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**** ESF Programme ****
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**** RELATIVISTIC EFFECTS IN HEAVY ELEMENT CHEMISTRY ****
**** AND PHYSICS ****
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Newsletter No. 13 (14. June 1995)
______________________________________________________________
Editor: Bernd Hess, hess@uni-bonn.de
Tel. 49-228-732920
FAX 49-228-732251
______________________________________________________________
The programme 'Relativistic Effects in Heavy-Element Chemistry and Physics'
('REHE') has been initiated by the European Science
Foundation in November 1992 and it is expected to run for 5 years, i.e.
from 1993 through 1997. The programme is intended to strengthen the in-
dicated "field" and to facilitate interactions between European scientists
concerned with related topics.
The 'Steering Committee' of the programme has at present the following
members:
E. J. Baerends (Amsterdam)
J.P. Daudey (Toulouse)
K. Faegri (Oslo)
I.P. Grant (Oxford)
B. Hess (Bonn, Vice-Chairman)
H. U. Karow (ESF)
J. Karwowski (Torun)
P. Pyykko (Helsinki, Chairman)
K. Schwarz (Vienna)
A. Sgamellotti (Perugia).
================================================================================
--- E D I T O R I A L
Please send material for the forthcoming newsletter to my attention,
hess@uni-bonn.de
The newsletter will be sent out every second month around the 10th day
of the month. Contributions should arrive in Bonn until the end of the
preceding month.
| The next newsletter (#14) is scheduled for Beginning of August 1995.
| Please send your contributions until end of July 1995.
Please send material >by e/mail< that enables us to fill the
following topics in forthcoming newsletters
All REHE newsletters are now available on www under URL
http://pcgate.thch.uni-bonn.de/tc/hess/esf/nl.html
================================================================================
--- F E L L O W S H I P S
In the framework of the REHE programme, there is support available
for visits of doctoral students and also for senior scientists at
institutions in a foreign partner country. This support covers visits
lasting 2-4 months ("long-term visits") which will give the holders
time to acclimatize to the methods used in the host laboratory as well as
short visits ("short-term visits") of only a few days.
Please send a short application detailing the project, the names of the
scientists involved and the aproximate date and duration of the visit
to either Pekka Pyykko or Bernd Hess. Please refer to REHE newsletter #7
for details.
Should the planned dates of your stay change for any reason, you are
requested to notify the Chairman as soon as possible with a copy to
the ESF.
================================================================================
--- R E S E A R C H N E W S AND R E L A T E D I N F O R M A T I O N
Summaries of recent research or comments to it (up to 1 page),
which are of general interest to the 'REHE' community, may
be submitted by any colleague preferrably by E-mail to my attention.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[communicated by Luuk Visscher]
Reference Dirac-Fock calculations using a gaussian nuclear model.
L. Visscher K. G. Dyall
University of Groningen NASA Ames Research Center
Luuk@chem.rug.nl Dyall@pegasus.arc.nasa.gov
At the final discussion of the ESF meeting in "Il Ciocco" it was concluded
that it is desirable to define a standard set of nuclear exponents for
calculations employing the gaussian finite nuclear model. This will make it
possible to compare total energies of different codes that use such a
model.
We propose the use of the model used in GRASP [1] to provide an generally
available reference point for basis set calculations. The nuclear exponent
, alpha, is defined by equating the root-mean-square value, rms, of the
nuclear charge distribution to the root-mean-square value (in atomic units)
of the gaussian distribution via the formula : alpha = 1.5 / (rms)**2. The
parameter rms can be related to the nuclear mass number, A, by the
empirical formula rms = 0.836 x A**(1/3) + 0.570 (with rms now given in
fm).
We have done a series of reference Dirac-Fock calculations based on this
model. The Hamiltonian used is the Dirac-Coulomb Hamiltonian. The speed of
light used is 137.0359895, the conversion factor Bohr/fm used is
52917.7249. As value for the atomic weight we chose the integer value of
the mass of the most abundant isotope of the elements. In table 1 the
resulting values of rms and alpha are given in atomic units.
The energies calculated are the weighted average energies of the
groundstate configurations. These are given in table 2. In table 3. some
energies of other low-lying configurations for the transition metals and
some of the lanthanides and actinides are given.
We hope that these values may serve as a reference for future (basis set)
calculations based on the Dirac-Coulomb Hamiltonian. A more detailed
discussion of the results of the calculations is planned to be published
elsewhere.
[1] K. G. Dyall, I. P. Grant, C. T. Johnson, E. P. Plummer and F. Parpia,
Comp. Phys. Comm. 50, 375 (1989).
Table 1. Nuclear masses, RMS radii (au) and exponents.
Element Nuclear parameters
Charge Mass RMS radius Gaussian Exponent
-------------------------------------------------------------
Hydrogen 1 1 2.6569547399E-05 2.1248239171E+09
Helium 2 4 3.5849373401E-05 1.1671538870E+09
Lithium 3 7 4.0992133976E-05 8.9266848806E+08
Beryllium 4 9 4.3632829651E-05 7.8788802914E+08
Boron 5 11 4.5906118608E-05 7.1178709563E+08
Carbon 6 12 4.6940079496E-05 6.8077502929E+08
Nitrogen 7 14 4.8847128967E-05 6.2865615725E+08
Oxygen 8 16 5.0580178957E-05 5.8631436655E+08
Fluorine 9 19 5.2927138943E-05 5.3546911034E+08
Neon 10 20 5.3654104231E-05 5.2105715255E+08
Sodium 11 23 5.5699159416E-05 4.8349721509E+08
Magnesium 12 24 5.6341070732E-05 4.7254270882E+08
Aluminum 13 27 5.8165765928E-05 4.4335984491E+08
Silicon 14 28 5.8743802504E-05 4.3467748823E+08
Phosphorus 15 31 6.0399312923E-05 4.1117553148E+08
Sulfur 16 32 6.0927308666E-05 4.0407992047E+08
Chlorine 17 35 6.2448101115E-05 3.8463852873E+08
Argon 18 40 6.4800211825E-05 3.5722217300E+08
Potassium 19 39 6.4346167051E-05 3.6228128110E+08
Calcium 20 40 6.4800211825E-05 3.5722217300E+08
Scandium 21 45 6.6963627201E-05 3.3451324570E+08
Titanium 22 48 6.8185577480E-05 3.2263108827E+08
Vanadium 23 51 6.9357616830E-05 3.1181925878E+08
Chromium 24 52 6.9738057221E-05 3.0842641793E+08
Manganese 25 55 7.0850896638E-05 2.9881373610E+08
Iron 26 56 7.1212829817E-05 2.9578406371E+08
Cobalt 27 59 7.2273420879E-05 2.8716667270E+08
Nickel 28 58 7.1923970253E-05 2.8996391416E+08
Copper 29 63 7.3633018675E-05 2.7665979354E+08
Zinc 30 64 7.3963875193E-05 2.7419021043E+08
Gallium 31 69 7.5568424848E-05 2.6267002737E+08
Germanium 32 74 7.7097216161E-05 2.5235613399E+08
Arsenicum 33 75 7.7394645153E-05 2.5042024280E+08
Selenium 34 80 7.8843427408E-05 2.4130163719E+08
Bromine 35 79 7.8558604038E-05 2.4305454351E+08
Krypton 36 84 7.9959560033E-05 2.3461213272E+08
Rubidium 37 85 8.0233033713E-05 2.3301551109E+08
Strontium 38 88 8.1040799081E-05 2.2839354730E+08
Yttrium 39 89 8.1305968993E-05 2.2690621893E+08
Zirconium 40 90 8.1569159980E-05 2.2544431039E+08
Niobium 41 93 8.2347219223E-05 2.2120420724E+08
Molybdenum 42 98 8.3607614434E-05 2.1458511597E+08
Technetium 43 98 8.3607614434E-05 2.1458511597E+08
Ruthenium 44 102 8.4585397905E-05 2.0965270287E+08
Rhodium 45 103 8.4825835954E-05 2.0846586999E+08
Palladium 46 106 8.5537941156E-05 2.0500935221E+08
Silver 47 107 8.5772320442E-05 2.0389047621E+08
Cadmium 48 114 8.7373430179E-05 1.9648639618E+08
Indium 49 115 8.7596760865E-05 1.9548577691E+08
Tin 50 120 8.8694413774E-05 1.9067718154E+08
Antimony 51 121 8.8910267995E-05 1.8975246242E+08
Tellurium 52 130 9.0801452955E-05 1.8193056289E+08
Iodine 53 127 9.0181040290E-05 1.8444240538E+08
Xenon 54 132 9.1209776425E-05 1.8030529331E+08
Cesium 55 133 9.1412392742E-05 1.7950688281E+08
Barium 56 138 9.2410525664E-05 1.7565009043E+08
Lanthanum 57 139 9.2607247118E-05 1.7490463170E+08
Cerium 58 140 9.2803027311E-05 1.7416744147E+08
Praseodynium 59 141 9.2997877424E-05 1.7343837120E+08
Neodynium 60 144 9.3576955934E-05 1.7129844956E+08
Promethium 61 145 9.3768193375E-05 1.7060044589E+08
Samarium 62 152 9.5082839751E-05 1.6591550422E+08
Europium 63 153 9.5267329183E-05 1.6527352089E+08
Gadolinium 64 158 9.6177915369E-05 1.6215880671E+08
Terbium 65 159 9.6357719009E-05 1.6155419421E+08
Dysprosium 66 162 9.6892647152E-05 1.5977529080E+08
Holmium 67 162 9.6892647152E-05 1.5977529080E+08
Erbium 68 168 9.7943009317E-05 1.5636673634E+08
Thulium 69 169 9.8115626740E-05 1.5581702004E+08
Ytterbium 70 174 9.8968651305E-05 1.5314257850E+08
Lutetium 71 175 9.9137288835E-05 1.5262201512E+08
Hafnium 72 180 9.9970978172E-05 1.5008710340E+08
Tantalum 73 181 1.0013585755E-04 1.4959325643E+08
Tungsten 74 184 1.0062688070E-04 1.4813689532E+08
Rhenium 75 187 1.0111259523E-04 1.4671710337E+08
Osmium 76 192 1.0191070333E-04 1.4442808782E+08
Iridium 77 193 1.0206865731E-04 1.4398142103E+08
Platinum 78 195 1.0238293593E-04 1.4309883584E+08
Gold 79 197 1.0269507292E-04 1.4223027307E+08
Mercury 80 202 1.0346628039E-04 1.4011788914E+08
Thallium 81 205 1.0392291259E-04 1.3888925203E+08
Lead 82 208 1.0437511130E-04 1.3768840081E+08
Bismuth 83 209 1.0452487744E-04 1.3729411599E+08
Polonium 84 209 1.0452487744E-04 1.3729411599E+08
Astatine 85 210 1.0467416660E-04 1.3690277000E+08
Radon 86 222 1.0642976299E-04 1.3242350205E+08
Francium 87 223 1.0657317899E-04 1.3206733609E+08
Radium 88 226 1.0700087100E-04 1.3101367628E+08
Actinium 89 227 1.0714259349E-04 1.3066730974E+08
Thorium 90 232 1.0784503195E-04 1.2897067480E+08
Protactinium 91 231 1.0770535752E-04 1.2930539512E+08
Uranium 92 238 1.0867476102E-04 1.2700881714E+08
Neptunium 93 237 1.0853744903E-04 1.2733038109E+08
Plutonium 94 244 1.0949065967E-04 1.2512299012E+08
Americium 95 243 1.0935561268E-04 1.2543221826E+08
Curium 96 247 1.0989359973E-04 1.2420711085E+08
Berkelium 97 247 1.0989359973E-04 1.2420711085E+08
Californium 98 251 1.1042580946E-04 1.2301273547E+08
Einsteinium 99 252 1.1055797721E-04 1.2271879740E+08
Fermium 100 257 1.1121362374E-04 1.2127611477E+08
Mendelevium 101 258 1.1134373034E-04 1.2099285491E+08
Nobelium 102 259 1.1147350119E-04 1.2071131346E+08
Lawrencium 103 260 1.1160293843E-04 1.2043147354E+08
Rutherfordium 104 261 1.1173204420E-04 1.2015331850E+08
Hahnium 105 262 1.1186082063E-04 1.1987683191E+08
Seaborgium 106 263 1.1198926979E-04 1.1960199758E+08
Unnilseptium 107 262 1.1186082063E-04 1.1987683191E+08
Unniloctium 108 265 1.1224519460E-04 1.1905722195E+08
Unnilennium 109 266 1.1237267433E-04 1.1878724932E+08
Table 2. Weighted energies (a.u) of groundstate configurations.
Element Valence configuration Weighted average energy
-------------------------------------------------------------
Hydrogen 1s1 -5.000066561265E-01
Helium 1s2 -2.861813322836E+00
Lithium He) 2s1 -7.433533135116E+00
Beryllium He) 2s2 -1.457589169824E+01
Boron He) 2s2 2p1 -2.453655424194E+01
Carbon He) 2s2 2p2 -3.767604073501E+01
Nitrogen He) 2s2 2p3 -5.432772189773E+01
Oxygen He) 2s2 2p4 -7.482498609906E+01
Fluorine He) 2s2 2p5 -9.950161528883E+01
Neon He) 2s2 2p6 -1.286919305477E+02
Sodium Ne) 3s1 -1.620780878320E+02
Magnesium Ne) 3s2 -1.999350669564E+02
Aluminum Ne) 3s2 3p1 -2.423307494688E+02
Silicon Ne) 3s2 3p2 -2.894613378333E+02
Phosphorus Ne) 3s2 3p3 -3.414946686908E+02
Sulfur Ne) 3s2 3p4 -3.985979302393E+02
Chlorine Ne) 3s2 3p5 -4.609383841595E+02
Argon Ne) 3s2 3p6 -5.286837628150E+02
Potassium Ar) 4s1 -6.015259539703E+02
Calcium Ar) 4s2 -6.797101614534E+02
Scandium Ar) 4s2 3d1 -7.633787393210E+02
Titanium Ar) 4s2 3d2 -8.528198251855E+02
Vanadium Ar) 4s2 3d3 -9.481886587231E+02
Chromium Ar) 4s1 3d5 -1.049596037818E+03
Manganese Ar) 4s2 3d5 -1.157321917868E+03
Iron Ar) 4s2 3d6 -1.271391985389E+03
Cobalt Ar) 4s2 3d7 -1.392001830426E+03
Nickel Ar) 4s2 3d8 -1.519305627226E+03
Copper Ar) 4s1 3d10 -1.653455075141E+03
Zinc Ar) 4s2 3d10 -1.794612983443E+03
Gallium Ar) 4s2 3d10 4p1 -1.942563763600E+03
Germanium Ar) 4s2 3d10 4p2 -2.097470360635E+03
Arsenicum Ar) 4s2 3d10 4p3 -2.259441912230E+03
Selenium Ar) 4s2 3d10 4p4 -2.428588274499E+03
Bromine Ar) 4s2 3d10 4p5 -2.605023485473E+03
Krypton Ar) 4s2 3d10 4p6 -2.788860623537E+03
Rubidium Kr) 5s1 -2.979805013301E+03
Strontium Kr) 5s2 -3.178079969233E+03
Yttrium Kr) 5s2 4d1 -3.383761823539E+03
Zirconium Kr) 5s2 4d2 -3.597083337324E+03
Niobium Kr) 5s1 4d4 -3.818148615074E+03
Molybdenum Kr) 5s1 4d5 -4.047141557025E+03
Technetium Kr) 5s2 4d5 -4.284113368334E+03
Ruthenium Kr) 5s1 4d7 -4.529269710325E+03
Rhodium Kr) 5s1 4d8 -4.782646287107E+03
Palladium Kr) 4d10 -5.044401093366E+03
Silver Kr) 5s1 4d10 -5.314634288967E+03
Cadmium Kr) 5s2 4d10 -5.593318837297E+03
Indium Kr) 5s2 4d10 5p1 -5.880431582337E+03
Tin Kr) 5s2 4d10 5p2 -6.176128089102E+03
Antimony Kr) 5s2 4d10 5p3 -6.480518627183E+03
Tellurium Kr) 5s2 4d10 5p4 -6.793698966609E+03
Iodine Kr) 5s2 4d10 5p5 -7.115794175183E+03
Xenon Kr) 5s2 4d10 5p6 -7.446895439744E+03
Cesium Xe) 6s1 -7.786771668333E+03
Barium Xe) 6s2 -8.135645011189E+03
Lanthanum Xe) 6s2 5d1 -8.493645715589E+03
Cerium Xe) 6s2 4f1 5d1 -8.861071487818E+03
Praseodynium Xe) 6s2 4f3 -9.238148527358E+03
Neodynium Xe) 6s2 4f4 -9.625131866514E+03
Promethium Xe) 6s2 4f5 -1.002209535915E+04
Samarium Xe) 6s2 4f6 -1.042916311399E+04
Europium Xe) 6s2 4f7 -1.084650507645E+04
Gadolinium Xe) 6s2 4f7 5d1 -1.127423020449E+04
Terbium Xe) 6s2 4f9 -1.171254530825E+04
Dysprosium Xe) 6s2 4f10 -1.216154577767E+04
Holmium Xe) 6s2 4f11 -1.262141333422E+04
Erbium Xe) 6s2 4f12 -1.309227053518E+04
Thulium Xe) 6s2 4f13 -1.357431706575E+04
Ytterbium Xe) 6s2 4f14 -1.406767725960E+04
Lutetium Xe) 6s2 4f14 5d1 -1.457253325274E+04
Hafnium Xe) 6s2 4f14 5d2 -1.508878660723E+04
Tantalum Xe) 6s2 4f14 5d3 -1.561663078504E+04
Tungsten Xe) 6s2 4f14 5d4 -1.615618541220E+04
Rhenium Xe) 6s2 4f14 5d5 -1.670762013174E+04
Osmium Xe) 6s2 4f14 5d6 -1.727108244859E+04
Iridium Xe) 6s2 4f14 5d7 -1.784678875058E+04
Platinum Xe) 6s1 4f14 5d9 -1.843491730915E+04
Gold Xe) 6s1 4f14 5d10 -1.903559509983E+04
Mercury Xe) 6s2 4f14 5d10 -1.964889615637E+04
Thallium Xe) 6s2 4f14 5d10 6p1 -2.027485064428E+04
Lead Xe) 6s2 4f14 5d10 6p2 -2.091371433185E+04
Bismuth Xe) 6s2 4f14 5d10 6p3 -2.156570607968E+04
Polonium Xe) 6s2 4f14 5d10 6p4 -2.223101317878E+04
Astatine Xe) 6s2 4f14 5d10 6p5 -2.290980761601E+04
Radon Xe) 6s2 4f14 5d10 6p6 -2.360210424554E+04
Francium Rn) 7s1 -2.430819334953E+04
Radium Rn) 7s2 -2.502818780985E+04
Actinium Rn) 7s2 6d1 -2.576236803465E+04
Thorium Rn) 7s2 6d2 -2.651090741186E+04
Protactinium Rn) 7s2 5f2 6d1 -2.727437880829E+04
Uranium Rn) 7s2 5f3 6d1 -2.805283995557E+04
Neptunium Rn) 7s2 5f4 6d1 -2.884700609464E+04
Plutonium Rn) 7s2 5f6 -2.965661751251E+04
Americium Rn) 7s2 5f7 -3.048262415700E+04
Curium Rn) 7s2 5f7 6d1 -3.132475585240E+04
Berkelium Rn) 7s2 5f9 -3.218383945308E+04
Californium Rn) 7s2 5f10 -3.305972228387E+04
Einsteinium Rn) 7s2 5f11 -3.395315531854E+04
Fermium Rn) 7s2 5f12 -3.486410104154E+04
Mendelevium Rn) 7s2 5f13 -3.579344389726E+04
Nobelium Rn) 7s2 5f14 -3.674135273222E+04
Lawrencium Rn) 7s2 5f14 6d1 -3.770804545159E+04
Rutherfordium Rn) 7s2 5f14 6d2 -3.869395524765E+04
Hahnium Rn) 7s2 5f14 6d3 -3.969954047093E+04
Seaborgium Rn) 7s2 5f14 6d4 -4.072527993600E+04
Unnilseptium Rn) 7s2 5f14 6d5 -4.177192864675E+04
Unniloctium Rn) 7s2 5f14 6d6 -4.283926465859E+04
Unnilennium Rn) 7s2 5f14 6d7 -4.392860174258E+04
Table 3. Weighted energies (a.u) of excited configurations.
Element Valence configuration Weighted average energy
-------------------------------------------------------------
Scandium Ar) 4s1 3d2 -7.633017349838E+02
Titanium Ar) 4s1 3d3 -8.527557574214E+02
Vanadium Ar) 4s1 3d4 -9.481359904421E+02
Chromium Ar) 4s2 3d4 -1.049638479896E+03
Manganese Ar) 4s1 3d6 -1.157288780278E+03
Iron Ar) 4s1 3d7 -1.271367404311E+03
Cobalt Ar) 4s1 3d8 -1.391985182445E+03
Nickel Ar) 4s1 3d9 -1.519296380884E+03
Copper Ar) 4s2 3d9 -1.653457381098E+03
Yttrium Kr) 5s1 4d2 -3.383699991150E+03
Zirconium Kr) 5s1 4d3 -3.597041525888E+03
Niobium Kr) 5s2 4d3 -3.818168261792E+03
Molybdenum Kr) 5s2 4d4 -4.047137383664E+03
Technetium Kr) 5s1 4d6 -4.284142765323E+03
Ruthenium Kr) 5s2 4d6 -4.529213844130E+03
Rhodium Kr) 5s2 4d7 -4.782562817239E+03
Palladium Kr) 5s2 4d8 -5.044280576747E+03
Palladium Kr) 5s1 4d9 -5.044392702838E+03
Silver Kr) 5s2 4d9 -5.314492518156E+03
Lanthanum Xe) 6s2 4f1 -8.493543577267E+03
Cerium Xe) 6s2 4f2 -8.860997696337E+03
Gadolinium Xe) 6s2 4f8 -1.127424286462E+04
Hafnium Xe) 6s1 4f14 5d3 -1.508870323453E+04
Tantalum Xe) 6s1 4f14 5d4 -1.561656433577E+04
Tungsten Xe) 6s1 4f14 5d5 -1.615613790559E+04
Rhenium Xe) 6s1 4f14 5d6 -1.670759321577E+04
Osmium Xe) 6s1 4f14 5d7 -1.727107755328E+04
Iridium Xe) 6s1 4f14 5d8 -1.784680715349E+04
Platinum Xe) 6s2 4f14 5d8 -1.843487443919E+04
Gold Xe) 6s2 4f14 5d9 -1.903552668278E+04
Actinium Rn) 7s2 5f1 -2.576220117866E+04
Thorium Rn) 7s2 5f2 -2.651071216115E+04
Protactinium Rn) 7s2 5f3 -2.727427421756E+04
Uranium Rn) 7s2 5f4 -2.805276519816E+04
Neptunium Rn) 7s2 5f5 -2.884696040862E+04
Curium Rn) 7s2 5f8 -3.132479317126E+04
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[communicated by M. Barysz]
Maria Barysz has been working with prof.Geerd Diercksen,
in Max-Planck-Institut in Garching from 05.05.95 till 05.07.95.
She has been continuing the project aimed at studing
an interplay between electron correlation and relativistic effects using
different kinds of scalar relativistic approximations to
to beyond-Hartree-Fock methods.
During this two month stay in Garching studies
on generalizations of single and multireference
coupled cluster approach using the algebraic no-pair
scalar relativistic theory of Hess and also some
versions of Pauli-like approximations will be performed.
Works on scalar relativistic CI will also be continued.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[communicated by Timo Fleig]
Dear Prof. Hess,
As requested, I summarize the results of the Bonn-Lund collaboration with
Dr. Jeppe Olsen from March 8 to March 22. The application No. 6/95 in the
REHE accounts was accepted on 2 March, 1995.
We are planning to develop a spin-dependent CASSCF program, employing the
two component formalism of the no-pair approach and the appropriate
kinematic and spin-orbit Hamiltonians.
The main task during these two weeks was to construct an antihermitean
operator for carrying out the orbital rotations in the MCSCF optimization.
The molecular orbital basis to be used consists of functions and their
time-reversed pendants, so a basis of Kramers spinors which are expanded
in a scalar manner in atomic spinors and complex coefficients. We set up
a general rotation operator in second quantization in the aforementioned
basis containing four independent optimization parameters. The introduction of
Kramers symmetry is now imposed by constructing the time-reversed one-particle
operators. As the excitation operators transform in the same fashion as the
orbitals, we evaluate commutators up to first order in a
Baker-Campbell-Hausdorff expansion which directly leads to expressions
restricting the degrees of freedom in the unitary transformations. The final
result is then an antihermitean operator which is to be used in a general
parametrization of the CASSCF wavefunction. As a conclusion, incorporation
of Kramers symmetry allows a reduction to two independent optimization
parameters.
The minimization itself is to be carried out by making use of the Super-CI
method with a Hessian approximation by Malmqvist, Rendell and Roos. The
possibility of performing a determinant-based CI (method by Olsen et al.) in
the present spin-dependent case was discussed in detail. The integration
of the program into the MOLCAS program package was reasoned with but decisions
in this respect have not yet been made.
Finally, we want to continue the successful cooperation with the group in
Lund on this project in the near future.
Timo Fleig
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[communicated by Kornel Sailer]
Dr. Christian Hofmann has been working with us on the examination of
relativistic effects in atomic systems. He considered the influence of the
nuclear structure on the electron-positron pair emission rate in internal pair
conversion of excited heavy-ions. This takes into account that the pair
creation does not only proceed via the exchange of a virtual photon, which is
emitted in the nuclear transition, but also by the penetration of the electron
and positron wave functions into the decaying nucleus. Since the pair
production occurs in the strong electromagnetic field of a highly-charged
nucleus we have to solve the Dirac equation for the Coulomb potential. We
calculated the spherical continuum wave functions assuming a point-like
or an extended nucleus. To determine the angular distribution of electrons
and positrons we also utilize the exact scattering solutions.
For a first estimation of the penetration effect we chose a surface-current
approximation, which was earlier employed to calculate the dynamical matrix
elements in the case of bound state conversion. Restriction of the nuclear
current to the nuclear surface results in a factorization of the pair
conversion matrix element into a part which describes the emission of a
photon by the decaying nucleus and a part which represents the electronic
continuum-continuum transition. Normalizing the pair conversion probability
by the photon emission probability yields an expression involving only the
electron and positron wave functions. This expression is evaluated numerically.
We found that the pair emission rate for electric nuclear transitions are
weakly affected by the penetration effects, while the magnetic pair
conversion is rather sensitive and leads for highly-charged nuclei to a
measurable deviation from the calculations performed by neglecting the
penetration effect. In the following we will apply a more realistic model
for the nuclear current within the framework of a collective nuclear model.
In addition to the calculations of Dr. Christian Hofmann concerning the
angular correlation of electron-positron pairs emitted by nuclear transitions
following Coulomb excitation, the theory of internal pair conversion would
then be completed.
The obtained results may help to shed more light on the results obtained
by the collaborations EPOS and ORANGE at the GSI, Darmstadt (Germany),
which encountered narrow line structures in the electron and positron
coincidence spectra measured in heavy-ion collisions at the Coulomb barrier.
These line structures, though not confirmed by another collaboration, APEX,
in Argonne (USA), lack any explanation up to now. Even if simulations
based on internal pair conversion will not reproduce these line structures,
the information about the pair emission rate and the angular distribution
is valuable to estimate the nuclear contribution to the background.
Yours sincerely
Kornel Sailer
Head of the Dept. for Theoretical Physics
Kossuth Lajos University, Debrecen, Hungary
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[communicated by Laszlo Szunyogh ]
******************************************
Spin-polarized Auger electron spectroscopy
******************************************
Report on a scientific stay of Dr. Laszlo Szunyogh (Institute of
Physics, Technical University of Budapest) with Prof. Dr. Hubert Ebert
at the Institute for Physical Chemistry of the University Munich
20th - 28th April 1995
During the first part of my stay I participated at the REHE-funded
workshop "Spin-orbit influenced spectroscopies of magnetic solids" at
Herrsching close to Munich (20th - 23th April 1995). As an oral
contribution I reported on our recent work concerning a relativistic
study of the magnetism of 4d and 5d adlayers on Ag(001) and Au(001)
surfaces. In contrast to previous scalar-relativistic calculations
predicting the occurrence of spontaneous spin magnetism mainly for
monolayers, it was found that apart from some few exceptions spin-orbit
coupling suppresses the formation of permanent spin moments. A simple
explanation for this finding could be given in terms of the Stoner model
due to spin-orbit coupling induced hybridization.
The second part of the stay I spent in Munich working with the group of
Prof. Ebert. The aim of the recently started common project is to
extend the relativistic Auger electron spectroscopy (AES) program,
developed by Szunyogh, Weinberger and Redinger (Phys. Rev. B, 46:2015,
1992) for paramagnetic systems, to a spin-polarized version in order to
get access to magnetically ordered systems as well as to spin-orbit
coupling induced phenomena in ferromagnetic systems. The underlying
formalism was reconsidered in detail because the new program version is
planned to give (in contrast to its fore-runner) spin- and
angle-resolved spectra. Apart from this new feature, the implementation
requires primarily the replacement of the Dirac equation solver for the
valence and core states as well as a corresponding adaptation of the
loops over various quantum numbers. Routines handling spin-polarized
relativistic scattering for the valence states have been developed and
used by both partners in the past (see above) and there was a very
fruitful exchange of experiences in that field. The core solver for the
new program comes from the Munich group and all technical details of its
inner working structure as well as its interface were discussed and
documented. The next steps in setting up the new AES program will be
done primarily in Budapest. It was agreed to meet the next time in
Vienna together with Prof. Peter Weinberger - presumably in July 1995 -
to combine the work done in the meantime and to discuss the further steps.
Future applications of the new package are planned to go in line with
corresponding experimental work done within the project "Zirkular
polarisierte Synchrotronstrahlung: Dichroismus, Magnetismus und
Spinorientierung" run by the German Ministry for Research and Technology
(BMFT).
We thank the ESF and the organizers of the REHE-network for the
financial support making this stay possible.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
================================================================================
--- P A P E R S F U N D E D B Y R E H E
>>> please send a preprint of papers funded by REHE to Bernd A. He\ss,
>>> Institut f\"ur Physikalische und Theoretische Chemie, Universit\"at Bonn,
>>> 53115 Bonn, Germany
--- S. Keller and C.T. Whelan
On the plane wave Born approximation for relativistic (e,2e) processes
published in J. Phys. B 27, L771
--- C.T. Whelan, H. Ast, S. Keller, H.R.J. Walters, and R.M. Dreizler
Triply differential cross sections in energy sharing symmetric geometry
for gold and uranium at relativistic impact energies
published in J. Phys. B 28, L 33
supported by REHE grants 7-93 and 16-93
================================================================================
--- C O N F E R E N C E N E W S
'Conference News' (in general they should NOT overrun about 1 page)
may be provided by organizers or their scientific secretaries. --
For meetings and workshops supported by ESF the submission of such
a report is a m u s t . To facilitate my job the reports should
be forwarded to my attention via E-mail.
Also please send information about conferences that might be of interest
for the members of the REHE community.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[communicated by H. Ebert]
SPIN-ORBIT INFLUENCED SPECTROSCOPIES OF MAGNETIC SOLIDS
a workshop funded by the ESF - prorgamme
RELATIVISTIC EFFECTS IN HEAVY ELEMENT CHEMISTRY AND PHYSICS
(coord.: P. Pyykk"o, Helsinki and B. Hess, Bonn)
and the EU-HCM - network:
AB INITIO (FROM ELECTRONIC STRUCTURE)
CALCULATION OF COMPLEX PROCESSES IN MATERIALS
(coord.: W. Temmerman, Daresbury)
at Herrsching (D), from 20.- 23. April 1995
organized by H. Ebert and G. Sch"utz
The aim of the workshop was to bring together researchers from
all over Europe, active in the field of Spin-orbit influenced
spectroscopies of magnetic solids and related topics, to present
and discuss their latest results and ideas.
Due to the fact that the workshop was funded by the ESF-network
on "RELATIVISTIC EFFECTS IN HEAVY ELEMENT CHEMISTRY AND PHYSICS"
(REHE) as well as the EU-HCM network of band structure theorists
AB INITIO (FROM ELECTRONIC STRUCTURE) CALCULATION OF COMPLEX
PROCESSES IN MATERIALS it was possible to bring together a great
number of theorists and experimenalists active in this field.
The ratio between theorists and experimentalists was about 1:1,
resulting in very fruitful discussions after the talks but also
during coffee breaks and in the evening in the so-called Magnetic
Bierstube.
Consistently with the title of the workshop various contributions
(see programme and abstracts below) reflected many different
possibilities in which the spin-orbit interaction can influence the
spectroscopical properties of magnetic solids -just giving rise to
some additional structure in the spectra or to phenomena not
present in paramagnets. The magneto-optical Kerr-effect, -a
classical example for this was addressed by J. K"ubler, P. Oppeneer,
D. Weller, and -in its non-linear form- by W. H"ubner.
Relativistic effects and magnetic dichroism in photoemission
for valence (J. Braun, A. Rampe) as well as core electrons
(U. Hillebrecht, G. van der Laan) were discussed. A theory to
describe the Auger-spectroscopy of magnetic systems was presented
by P. Weinberger.
Most contributions (talks by D. Arvanitis, M. S. S. Brooks,
K. Capelle, P. Carra, C. T. Chen, H. Ebert, A. Fontaine, G.-Y. Guo,
H. K"onig, G. Krill, G. Sawatzky, J. St"ohr, P. Strange, as well
as posters by D. Schmitz and J. Schwitalla) were related to magnetic
dichroism in X-ray absorption (XAS). The main issue of these talks
was the validity and applicability of the sum rules to deduce spin-
and orbital magnetic moments from experimental spectra. For this
reason the contributions of M. S. S. Brooks, B. Johansson, and
L. Szunyogh on the importance of the spin-orbit coupling and the
orbital polarisation mechanism for these moments perfectly fitted
into the programme. XAS at high energies i.e. magnetic EXAFS and the
interpretation of the corresponding spectra were addressed by
C. Brouder and G. Sch"utz. The inverted XAS i.e. magnetic dichroism
in fluorescence was the topic of B. Gyorffy's talk. Applications of
the magnetic dichroism in XAS to investigate magnetic coupling and
domain structures were presented by C. T. Chen and C. M. Schneider.
M. J. Cooper's and K. Baberschke's talks on Compton scattering and
ferromagnetic resonance, respectively, demonstrated that XAS is not
the one and only tool to get information on spin- and orbital
magnetism. A scheme to treat the relativistic effects in an
approximate way and its application to scattering at free atoms was
presented by L. Fritsche. Finally, P. Pyykk"o reminded us that spin-
orbit coupling has its impact not only on electron spectroscopies but
also for example in nuclear quadrupole resonance spectroscopy.
(Hubert Ebert and Gisela Sch"utz)
PROGRAMME
---------
Friday, April 21.
----------------
J. K"ubler, Darmstadt
Calculated magneto-optical properties of transition metals and their
compounds
D. Weller, San Jose
Magneto Optical Spectroscopy in strongly anisotropic systems: FePt
and Co
M. S. S. Brooks, Karlsruhe
Relativistic Effects in Actinides
P. M. Oppeneer, Dresden
Spin-orbit transmission effects in the Kerr spectra of compounds:
an ab initio study
W. H"ubner, Berlin
Nonlinear Magneto-Optical Response of Thin Ferromagnetic Films
G. Sawatzky}, Groningen
Magnetic X-Ray dichroism in studies of both short and long range
magnetic order in antiferromagnetica
G. Krill, Orsay
Magnetic Circular X-ray Dichroism in RE/TM intermetallic compounds
Role of the hybridization between 4f and the conduction electrons
G.-Y. Guo, Daresbury
Band Theoretical Investigation of Circular Magnetic X-ray
Dichroism Sum Rules for Magnetic Multilayers
D. Arvanitis, Uppsala
An angle dependent MCXD study of Ni, Co and Fe on Cu(100);
Experiment versus Theory
M. J. Cooper, Warwick
Spin and orbital moments in rare earth ferromagnetic compounds
studied by Compton scattering
B. L. Gyorffy, Bristol
Dichroism in X-ray Fluorescence
B. Johansson, Uppsala
Enhancement of orbital magnetic moments at surfaces
C. Brouder, Paris
Multiple-scattering approach to magnetic EXAFS
Saturday, April 22.
------------------
P. Weinberger, Wien
Relativistic AES
U. Hillebrecht, D"usseldorf
Angular dependent magnetic dichroism in core level photoemission
G. van der Laan, Daresbury
Magnetic Ground State Properties and Angular Dependent Magnetic
Dichroism in Core Level Photoemission
A. Rampe, Aachen
Linear magnetic dichroism in the angular distribution of photo-
electrons (LMDAD) from the valence bands of Co(0001) and Fe(110)
G. Sch"utz, Augsburg
Magnetic EXAFS
P. Carra, Grenoble
Unified approach to near-edge X-ray phenomena
C. T. Chen, Murray Hill
Orbital and spin magnetic moments from soft-X-ray MCD
A. Fontaine, Orsay
Spin polarization of conduction electrons in metallic multilayers
and intermetallic compounds from X-ray magnetic circular dichroism
J. St"ohr, San Jose
Angle-Dependent XMCD - Probing the Microscopic Origin of Magnetic
Anisotropy
H. Ebert, M"unchen
Multiple scattering approach to magnetic dichroism in electron
spectroscopy of transition metal systems
K. Baberschke, Berlin
Ni and Co single layers: Thickness dependence of Tc, the magnetic
moment and the anisotropy
L. Szunyogh, Budapest
Relativistic study of magnetism of 4d, 5d transition metal
overlayers on Ag(001) and Au (001)
C. M. Schneider, Berlin
Imaging of magnetic domains by means of magnetic dichroisms:
magnetic spectro-microscopy
Sunday, April 23.
----------------
K. Capelle, W"urzburg
Off-Diagonal Spin-Orbit Coupling in Superconductors
H. K"onig, Grenoble
X-ray Absorption in a Tight-binding Band Structure Approach
P. Strange, Keele
On the Interpretation of MXCD Experiments on Itinerant Magnets
L. Fritsche, Clausthal-Zellerfeld
Treating Electronic excitations in Magnetic Materials by Solving
Fully Relativistic Two-Component One-Particle Equations
J. Braun, Osnabr"uck
Relativistic effects in inverse photoemission
P. Pyykk"o, Helsinki
Relativistic effects on nuclear quadupole coupling
List of Participants
--------------------
D. Arvanitis (Uppsala), M. Battocletti (M"unchen), K. Baberschke (Berlin),
G. Bauer (Delft), J. Braun (Osnabr"uck), M. S. S. Brooks (Karlsruhe),
C. Brouder (Paris), K. Capelle (W"urzburg), P. Carra (Grenoble),
C. T. Chen (Murray Hill), M. J. Cooper (Warwick),
P. H. Dederichs (J"ulich), M. Deng (M"unchen), C. Demangeat (Strasbourg),
H. A. D"urr (Daresbury), H. Ebert (M"unchen), R. Feder (Duisburg),
L. Fritsche (Clausthal), H. Freyer (M"unchen), A. Fontaine (Orsay),
J. Goedkoop (Grenoble), G. G"untherodt (Aachen), G.-Y. Guo (Daresbury),
B. L. Gyorffy (Bristol), U. Hillebrecht (D"usseldorf),
D. Hartmann (Aachen), W. H"ubner (Berlin), B. Johansson (Uppsala),
G. Kaindl (Berlin), P. Kienle (M"unchen), E. Kisker (D"usseldorf),
M. Knecht (M"unchen), H. K"onig (Grenoble), G. Krill (Orsay),
J. K"ubler (Darmstadt), M. Mikami (Yokohama), P. M. Oppeneer (Dresden),
P. Pyykk"o (Helsinki), A. Rampe (Aachen), G. Sawatzky (Groningen),
D. Schmitz (J"ulich), C. M. Schneider (Berlin), G. Sch"utz (Augsburg),
J. Schwitalla (M"unchen), J. St"ohr (San Jose), P. Strange (Keele),
Z. Szotek (Daresbury), L. Szunyogh (Budapest),
W. M. Temmerman (Daresbury), G. van der Laan (Daresbury),
A. Vernes (M"unchen), P. Weinberger (Wien), W. Weber (M"unchen),
D. Weller (San Jose)
A list of the addresses of the participants as well as a LATEX-
version of this report is available upon request (email) from
H. Ebert.
ABSTRACTS
---------
AN ANGLE DEPENDENT MCXD STUDY OF NI, CO AND FE ON CU(100);
EXPERIMENT VERSUS THEORY
J. Hunter Dunn (1), D. ARVANITIS (1), N. Martensson (1),
M. Tischer (2), F. May (2), M. Russo(2), K. Baberschke (2)
(1) Physics Department, Uppsala University, Box 530,
S-75121 Uppsala, Sweden
(2) Institut f"ur Experimentalphysik, Freie Universit"at Berlin,
Arnimallee 14, D-14195 Germany
We report MCXD measurements of Ni, Co and Fe overlayers on a
Cu(100) surface. The samples were prepared and characterized in
situ, in ultra high vacuum. Out of plane elliptical X-ray light
was used from a bending magnet at the storage ring BESSY in
combination to an SX 700 plane grating monochromator. Data were
collected around the overlayer L3,2 edges. MCXD measurements as
a function of the X-ray incidence angle for thicker overlayers
show that saturation effects clearly modify the intensity
distribution of the L3,2 peak heights for the grazing X-ray
incidence angles. This effect is therefore particularly important
in the case where the magnetization easy axis is parallel to the
surface. We have taken saturation effects into account before
deriving information on magnetic moments using MCXD sum rules.
By applying the sum rules to thick overlayers we find values for
the magnetic moments that differ from the known ground state ones
[1]. Possible reasons for this discrepancy will be discussed. One
such contribution to the MCXD signal, is the existence of final
states of s character. We present experiments of controlled oxygen
contamination in the case of Ni overlayers on Cu(100) that allow
one to quantify experimentally the MCXD contribution of these
states. These experiments also yield information on the influence
of light contaminants on the magnetic properties of metal overlayers.
[1] J. Hunter Dunn, D. Arvanitis, N. Martensson, M. Tischer,
F. May, M. Russo, K. Baberschke, J. Phys. C 7, 1111(1995)
%%%
NI AND CO SINGLE LAYERS:
THICKNESS DEPENDENCE OF TC, THE MAGNETIC MOMENT AND THE ANISOTROPY
K. BABERSCHKE (1), M. Tischer, B. Schulz, A. Aspelmeier,
M. Farle, D. Arvanitis
(1) Inst. f"ur Atom- und Festk"orperphysik (WE 1), Freie
Universit"at Berlin, Arnimallee 14, D-14195 Berlin - Dahlem
MCXD /1/, ferromagnetic resonance /2/, and susceptibility /3/
measurements are reported for Ni and Co single layers mostly on
Cu(100). Emphasis is given to the full thickness dependence of Tc
and the critical exponent beta and in addition to the temperature
dependence of M(T) and the anisotropy energy K(T). It appears to be
important to analyze K as function of the reduced temperature
t = T/Tc. The "surface" contribution of K is separated and the
origin of a crossover between in- and out-of-plane will be discussed.
In the ultrathin limit an enhancement of the ratio orbital/spin
moment is measured for Co/Cu(100) and a reduction of the total moment
can be seen for Ni/Cu(100). For the later case the anisotropy of the
magnetic moment can also be seen.
/1/ M. Tischer et al. Surf. Sc. 307, 1096 ('94)\\
/2/ B. Schulz et al. Phys. Rev. B50, 13467 ('94)\\
/3/ M. Tischer et al. J. MMM 135, L1 ('94)\\
%%%
RELATIVISTIC EFFECTS IN INVERSE PHOTOEMISSION
J. BRAUN
Universit"at Osnabr"uck
The relativistic one-step theory is applied to inverse photoemission
from the Ir(111)-surface. In the framework of a completely new
developed surface contribution theoretical spectra are compared with
corresponding experimental data. Herein the matrix elements for the
surface contribution have been calculated in considering the image-
potential behaviour of the barrier. Furthermore, it will be shown
that relativistic effects induced by the bulk crystal modify the
calculated spectra.
%%%
RELATIVISTIC EFFECTS IN ACTINIDES
M.S.S. BROOKS (1), A. Delin (2), O. Eriksson (2) and
B. Johansson (2)
(1) European Commission, European Institute for Transuranium
Elements, Postfach 2340, D-76125 Karlsruhe, Federal Republic
of Germany
(2) Condensed Matter Theory Group, Institute of Physics,
University of Uppsala, BOX 530, S-75121, Uppsala, Sweden
The effect of spin-orbit coupling upon the calculated pressure-
volume relationship and upon the magnetic equation of state is
summarized.
The local, diffuse and orbital magnetization and moment densities
of 3d transition metals and actinides are compared. In the
actinides the diffuse moments (mostly 6d in character) are anti-
parallel to the local spin moments (mostly of 5f character) whereas
the orbital moments (mostly of 5f character) are anti-parallel to
the local spin moments and very large. Neutron diffraction results
are analysed and comparison with theory yields the ground state
spatial local, diffuse and orbital ground state magnetization
densities. In particular the large orbital moments in actinides
have been both measured and calculated from first principles.
Initial results for M4 and M5 edge magnetic circular dichroism in
actinides selects primarily the 5f orbital moment, resolved in
energy. Calculations of the magneto-optical Kerr effect for the
actinide compound US, while agreeing with measurements in the 2eV
range, produce a peak at 4eV which is not observed.
%%%
SPIN-ORBIT EFFECTS IN SUPERCONDUCTORS WITH HEAVY ELEMENTS
KLAUS CAPELLE
Institut f"ur Theoretische Physik, Universit"at W"urzburg
Starting from a recently proposed relativistic theory of super-
conductivity, the counterparts of the Dirac equation and the Pauli
equation are derived for superconductors. In the non-relativistic
limit the conventional theory of superconductivity is regained. Up
to order $(v/c)^2$ one obtains, besides the usual Darwin, spin-
orbit and kinetic energy corrections, new off-diagonal spin-orbit
and Darwin terms involving the pair potential in place of the
electrostatic potential. These previously unknown terms are
relevant for superconductors which contain heavy elements or have
a small coherence lenght. The effect of the spin-orbit terms on
dichroism in superconductors is investigated. It turns out that
there are three ways to produce dichroism in a superconductor:
(i) external magnetic fields (Faraday/Kerr effect),
(ii) internal magnetic fields (magnetic superconductors) and
(iii) unconventional order parameter.
In all three cases the effect of the new off-diagonal terms is an
additional contribution to the total dichroism below the critical
temperature.
%%%
ORBITAL AND SPIN MAGNETIC MOMENTS FROM SOFT-X-RAY MAGNETIC
CIRCULAR DICHROISM
C. T. CHEN
AT\&T Bell Laboratories, 600 Mountain Avenue, Murray Hill,
NJ 07974, USA
High precision, L2,3-edges photoabsorption and magnetic circular
dichroism spectra of iron and cobalt were measured by the
transmission method with in-situ grown thin films, eliminating
experimental artifacts encountered by the indirect methods used in
all previous measurements. The magnetic moments determined
from the integrals of these spectra, according to the x-ray magnetic
circular dichroism sum-rules, are found to be in excellent agreement
(within 3\%) for the orbital to spin moment ratios, and in good
agreement (within 8\%) for the individual moments, with those
obtained from Einstein-de Haas gyromagnetic ratio measurements,
demonstrating decisively the applicability of the individual orbital
and spin sum-rules to these two itinerant magnetic systems. The
general verification and applicability of the individual sum-rules
to magnetic systems and the caveats for total electron and
fluorescence yield x-ray magnetic circular dichroism measurements
will be discussed.
%%%
SPIN AND ORBITAL MOMENTS IN RARE EARTH FERROMAGNETS
M. J. COOPER
Department of Physics, University of Warwick,
Coventry CV4 7AL, UK
Magnetic Compton scattering is a technique that allows the spin-
dependent momentum distribution in ferromagnets to be studied [1].
In alloys and compounds that contain dissimilar elements the
momentum distribution of the electrons with unpaired spins are
sufficiently different to allow the site specific spin moments to
be separated from each other. This has been demonstrated in rare-
earth compounds such as HoFe2, ErFe2 and DyFe2 [2]. The spin
moments can be followed as a function of temperature leading to
the direct observation of spin compensation temperatures in
compounds with antiferromagnetic coupling between the two sites
[3]. In addition if the data on spin moments are combined with
bulk magnetisation results some statement about the orbital
component can be made.
The experiments reffered to above have been largely concerned with
exploring the scope of this new technique and the actual moments
in these materials are considered to be well-known. However
measurements have recently been made on CeFe2 where there is a
pronounced difference between the calculated 4f moment [4] and that
deduced from neutron data [5]. Our results show that the Ce 4f
moment is very small - less than 0.1 mu_B which is in agreement
with the neutron result and markedly different to the calculated
value which is some four times larger. On the other hand the Ce 5d
moment is higher than that inferred from the neutron measurement.
These data together with those for UFe2 will be discussed.
[1] Cooper et al. J Phys Condensed Matter {\bf 4} L399 1992
[2] Lawson et al. J Phys Condensed Matter {\bf 7} 389 1995
[3] Cooper et al. Phys Rev Letts. {\bf 71} 1095 1993
[4] Eriksson et al. Phys Rev Letts. {\bf 60} 2523 1988
[5] Kennedy et al. J Phys Condensed Matter {\bf 5} 5169 1993
%%%
MULTIPLE SCATTERING APPROACH TO MAGNETIC DICHROISM IN ELECTRON
SPECTROSCOPY OF TRANSITION METAL SYSTEMS
H. EBERT, J. Schwitalla and G. -Y. Guo
Inst. f"ur Physikalische Chemie Universit"at M"unchen,
Theresienstr. 37, D-80333 M"unchen
A rigorous and parameterfree description of magnetic X-ray
dichroism (MXD) and other related phenomena requires to deal with
magnetism as well as relativistic effects on equal footing. A
corresponding description of the electronic structure within the
framework of spin-density functional theory is sketched in short.
As a first step to go beyond this scheme inclusion of the magnetic
interaction is discussed. To allow for a detailed discussion of
the role of spin-orbit coupling a model Hamiltonian to be used
within multiple scattering schemes has been derived that allows
to scale the spin-orbit coupling strength without affecting other
relativistic effects. Corresponding calculations of orbital magnetic
moments MOKE- as well as MXD-spectra demonstrate the usefulness of
the approach. Finally theoretical MXD-spectra in Cu-Co-alloys will
be presented and discussed in some detail.
%%%
SPIN POLARISATION OF CONDUCTION ELECTRONS IN METALLIC MULTILAYERS
AND INTERMETALLIC COMPOUNDS EVIDENCED BY X-RAY MAGNETIC CIRCULAR
DICHROISM
A. FONTAINE (1,2), S. Pizzini (1), R. M. Galera (1),
F. Baudelet (3,4), J. F. Bobo (4), Ch. Giorgetti (3),
E. Dartyge (3), M. Piccuch (4)
(1)Laboratoire L. Neel CNRS BP 166X F-38042 Grenoble
(2)ESRF BP 220 F-38043-Grenoble
(3)LURE CNRS-CEA-MESR Bat 209d 91405 ORSAY
(4)Laboratoire de Physique des Solides BP 239 F-54506 Vandoeuvre
les Nancy
After a delay of almost a century, synchrotron radiation has been
able to associate the original ideas on magnetism of Zeeman and the
discovery of X-rays by R"ontgen. In the hard X-ray range, it is
possible to produce polarisation-tunable sources using an additional
optical device, the phase plate which opens up new classes of X-ray
spectroscopies and new resonant methods of diffraction for magnetic
materials. The main lines of X-ray magnetic circular dichroism at
K-edge of the 3d elements, are discussed in term of hybridisation
of the 4p-probed band with the spin polarized and orbital momentum-
polarized d band. Results on very appealing materials such Cu-Co,
Cu-Fe multilayers which exhibit large magnetoresistance are
presented in term of spin polarisation of conduction electrons of
the copper layer. XMCD of Co/Cu and Fe/Cu multilayers at the copper
K edge shows:
i) that the p-band of copper is significantly spin-polarised by
the adjacent Co or Fe atoms;
ii) that the spin-polarisation of the copper layers strongly
depends on the adjacent magnetic layer;
iii) that the magnetic polarisation is not restricted to the
interface layer i. e. it departs from a simple 1/t(Cu)
dependence.
%%%
TREATING ELECTRONIC EXCITATIONS IN MAGNETIC MATERIALS BY SOLVING
FULLY RELATIVISTIC TWO-COMPONENT ONE-PARTICLE EQUATIONS
L. FRITSCHE
Institut f"ur Theoretische Physik der TU Clausthal,
Leibnizstr. 10 D--38678 Clausthal--Zellerfeld, Germany
As has been shown in a number of articles by the present author,
the Kohn-Sham version of density functional theory can be
extended to stationary excited N-electron states which amounts
to self-consistently solving N one-particle equations that have
primarily the form of Dirac equations. Within rather lenient
assumptions it is possible to reduce these equations to two-
component equations without resorting to Foldy-Wouthuysen trans-
formations. Hence, these equations hold to any order of v^2/c^2,
different from the familiar relativistic Pauli equations. They
contain an explicit expression for the spin-orbit coupling in the
general case of magnetic order and offer the advantage - among
other favorable aspects of numerical convenience - that they
reduce in the limit c to infinity to a pair of one-particle
Schr"odinger equations for the two spin orientations. The
capabilities of the new approach are demonstrated by results on
collision induced spin polarization of low energy electrons that
are scattered by heavy atoms.
%%%
MAGNETIC CIRCULAR DICHROISM IN X-RAY FLUORESCENCE: EXPERIMENT
C. F. HAGUE and J.-M. Mariot
Laboratoire de Chimie Physique Matiere et Rayonnement
(Unite associe au CNRS Universite Pierre et Marie Curie,
11 rue P. et M. Curie, 75231 Paris Cedex 05, France
Strange et al (Phys Rev Lett 1991) predicted that magnetic circular
dichroism in x-ray fluorescence spectra (XFS) would measure the
spin polarisation of valence states in a magnetically oriented
ferromagnet. The appeal of such an experiment is that it may
provide information concerning spin polarised hybridisation in
magnetic alloys which, unless the component valence states are well
separated, is not readily available even from spin polarised
photoemission. A technical point of interest also is that XFS is
relatively insensitive to surface effects which is of importance
when dealing with composite magnetic materials. We will present the
data measured so far and discuss some of the outstanding problems
related, either to the low efficiency of the experiment, or to the
multielectron effects inherent in the excitation spectra. Some
future experiments will be outlined.
%%%
ANGULAR DEPENDENT MAGNETIC DICHROISM IN CORE LEVEL PHOTOMEMISSION
U. HILLEBRECHT
Universit"at D"usseldorf
The use of linearly polarized light greatly facilitates studies of
magnetic dichroism in core level spectroscopy. If one uses a
chiral geometry in angle- resolved photoemission (MLDAD), the
information obtained is identical to that contained in circular
dichroism studies. The 3p and 2p levels of the 3d ferro- magnets
have been studied in this way, supplemented by spin-resolved photo-
electron detection. In such "complete" experiments the effects of
exchange and spin-orbit interaction can be separated. Studies of
the angular dependence of Fe and Co 3p MLDAD showed the influence
of both the atomic angle dependence as well as strong photoelectron
diffraction effects. The latter arise due to a dependence of the
scattering of the photoelectron on the angular momentum (l) and
magnetic (m) character of the final state. The present status and
prospects of combining photoelectron diffraction with magnetic
dichroism will be addressed.
%%%
NONLINEAR MAGNETO-OPTICAL RESPONSE OF THIN FERROMAGNETIC FILMS
W. H"UBNER, U. Pustogowa, and K. H. Bennemann
Institute for Theoretical Physics, Freie Universit"at,
Berlin, Germany
Nonlinear magneto-optics is a sensitive fingerprint of the elec-
tronic, magnetic and atomic structure of surfaces, interfaces and
thin films. We present a theoretical study of the nonlinear
magneto-optical Kerr-effect in Fe, which demonstrates how various
electronic material properties can be extracted from the nonlinear
Kerr spectrum. We derive its dependence on exchange interaction
and magnetization. We show that the Kerr rotation angle in second
harmonic generation (SHG) is enhanced by one order of magnitude
compared to the linear Kerr angle. Using the full-potential LMTO
method we calculate the thickness dependence of the nonlinear
Kerr spectra of thin Fe(001) films. We demonstrate how this
dependence can be used for the characterization of ultrathin films.
The polarization dependence of the SHG yield shows sensitively the
symmetry of surfaces and interfaces.
%%%
MAGNETIC CIRCULAR DICHROISM IN PHOTOEMISSION FROM LANTHANIDE MATERIALS
G. KAINDL
Institut f"ur Experimentalphysik, Freie Universit"at Berlin,
Arnimallee 14, D-14195 Berlin-Dahlem, Germany
We report on our investigation of magnetic circular dichroism (MCD)
in photoemission (PE) from magnetically ordered lanthanide
materials, in particular from single-crystalline films of Gd, Tb,
and Dy metal [1-3]. Particularly large MCD effects are expected for
well-resolved 4f^(n-1) PE multiplet spectra, amounting up to 93%
for the 8S7/2 component of the Tb-4f^7 PE spectrum, with 67%
observed [2]. An application of this new effect to a quantitative
measurement of the degree of circular polarization in the soft x-
ray region is discussed. Large MCD effects were also observed in
the 4d core-level PE spectra of Gd and Tb metal, which are well
accounted for by an atomic many-particle description [4]. Some
applications of this new element-specific tool to the study of
surface and interface magnetism are discussed:
(i) Magnetic properties of the close-packed (0001) surfaces of Gd
and Tb metall, and
(ii) Magnetic behavior of the hetero-magnetic interface 1 ML
Eu/Gd(0001)[5].
[1] K. Starke, E. Navas, L. Baumgarten, and G. Kaindl,
Phys. Rev. B {\bf 48}, 1329(1993).
[2] K. Starke, L. Baumgarten, E. Arenholz, E. Navas, and
G. Kaindl, Phys.Rev. B{\bf 50}, 1317(1994).
[3] E. Arenholz, E. Navas, K. Starke, L. Baumgarten, and
G. Kaindl, Phys. Rev. B{\bf 51}, xxx (1. April 1995).
[4] G. van der Laan, E. Arenholz, E. Navas, A. Bauer, and
G. Kaindl, Preprint(1995).
[5] E. Arenholz et al., to be published.
This work was supported by the BMFT, project 05-5KEAXI-3/TP01,
and the DFG, Sonderforschungsbereich 290/TP A06.
%%%
X-RAY ABSORPTION IN A TIGHT-BINDING BAND STRUCTURE APPROACH
HARALD K"ONIG (1), Bruce Harmon (2)
(1)European Synchrotron Radiation Facility, B.P. 220,
F-38043 Grenoble Cedex
(2)Ames Lab-USDOE and Dept. of Physics and Astronomy,
Iowa State University, Ames, Iowa 50011
We report the calculation of the X-ray Absorption Spectrum (XAS)
and Circular Magnetic X-ray Dichroism (CMXD) at the L$_3$-edge of
Dysprosium hcp metal. Using a LMTO-tight binding band structure
method, we study dipolar (E1) core hole absorption to wide band
final states. For heavy Rare Earth (RE) compounds, the LSDA
prescription results in the 4f minority spin states being pinned
at the Fermi level. Without spin-orbit coupling there is no
orbital moment and the spin moment is incorrect. Spin-orbit
coupling induces an orbital polarization of the 4f single
particle eigenstates, with orbital and spin moments close to
those of the corresponding RE ion in its Hund's rule ground state.
Adding a Coulomb repulsion term to the unoccupied 4f diagonal
elements of the Hamiltonian matrix, we shift these states to
energies well above the Fermi level to obtain integer occupation
of the 4f shell and correct spin moments for the 4f and 5d shells.
To account for quadrupole (E2) absorption to the narrow 4f final
states we use an atomic multiplet model for a Dy$^{3+}$ ion.
Combining E1 and E2 transitions, while accounting for their
different dependence on the angle between the incoming photon wave
vector and the magnetization direction, we explain the result of
recent experiments, thus establishing the E2 nature of the negative
feature at the low energy side of the Dy CMXD spectrum.
%%%
SPIN-ORBIT TRANSMISSION EFFECTS IN THE KERR SPECTRA OF COMPOUNDS:
AN AB INITIO STUDY
P.M. OPPENEER, V.N. Antonov, and T. Kraft
Max-Planck Research Group "Electron Systems"
University of Technology, D-01062 Dresden, Germany
The magneto-optical (MO) Kerr spectra of a number of transition-
metal and uranium compounds are studied from first principles,
using density-functional band-structure theory. The theoretical
Kerr spectra of the following transition-metal compounds will be
discussed:
(a) the Heusler alloys NiMnSb, PdMnSb, PtMnSb, PtMnSn, and Co2HfSn,
(b) the XPt$_3$ compounds, with X=V, Cr, Mn, Fe, and Co,
(c) the layered MnPt, FePt, and CoPt compounds, (d) the hexagonal
MnAs, MnSb, and MnBi compounds, and
(e) some Invar alloys.
Furthermore, the uranium monochalcogenides US, USe, and UTe are
investigated, as well as some ternary uranium intermetallics.
For the Heusler alloys, band-structure theory gives a very good
description of the measured Kerr spectra. Particularly the giant
Kerr rotation found experimentally in PtMnSb is straightforwardly
obtained. The Kerr spectra of the layered XPt (X=Mn, Fe, Co)
alloys are given for the (001), (111), and (110) orientation of
the magnetic moment. Large Kerr anisotropies are predicted in
these materials. For some of the XPt$_3$ compounds, theory also
predicts a giant Kerr rotation. The origin of the large Kerr
effect is analyzed by artificially changing the magnetic moments,
the spin-orbit coupling strength, and the optical transition-
matrix elements on each site. This reveals which interband
transitions are responsible for the Kerr rotation peak, and that
the large Kerr rotation is caused by a combination of the spin-
orbit coupling on Pt and the magnetic moment on X.
In case of the uranium compounds, the height and over-all shape
of the Kerr spectra is satisfactorily given by the single particle
LSDA approach. But when $5f$ electrons participate in the optical
transitions, the detailed agreement becomes less good. Thus, while
the LSDA does a perfect job for the MO spectra of transition-metal
compounds, for the uranium compounds we come to the limits of what
can be described within the LSDA.
%%%
RELATIVISTIC EFFECTS ON NUCLEAR QUADRUPOLE COUPLING
PEKKA PYYKK"O
Department of Chemistry, P.O.B. 55, FIN--00014 University of
Helsinki, Finland, E-mail: Pekka.Pyykko@helsinki.fi
Relativistic effects strongly influence the NMR or hyperfine
properties (chemical shifts, nuclear spin-spin coupling and nuclear
quadrupole coupling) of atoms, molecules or solids. As first shown
by Casimir in 1936 [1], for the two states j = l +/- s, three
radial electric field gradient integrals, q(++), q(+-), and q(--)
must be introduced. The relativistic correction factors, defined
for operator q as
$$ C = <{\rm R}\vert \hat q \vert {\rm R}>/<{\rm NR}\vert \hat q
\vert {\rm NR}>, $$
have quite different values for the three combinations. E.g. for
the bismuth atom ground state 6p shell at Dirac-Fock level, C(++)
and C(+-) are 1.28 and 1.91, respectively, while q(--) vanishes
entirely, due to j = 1/2. There also is a dependence on the n
quantum number [2]. In addition to these relativistic changes of
the integrals (at the atomic centre), spin-orbit tilting effects
may occur, even at light atoms, bonded to heavy ones.
Electric field gradients have been observed in half-closed-shell
atoms, whose S > 1/2, in free space and on cubic crystal sites.
Examples are the p^3 ,d^5 or f^7 atomic systems such as N-Bi, Mn
and Mn^{2+} or Gd^{3+}. The value of q grows faster than Z^6, from
1.27 Hz to 305.067(2) MHz for the series from N to Bi. The nature of
the effect was first understood by Sandars [3]. Similar effects are
known in cubic, magnetic solids.
We have produced Dirac-Fock-level electric field integrals for the
elements 1--94, investigated the hydrogen-like, n-dependent
correction factors, C and used simple molecular-orbital models for
estimating the spin-orbit tilting effects [4].
[1] H.B.G. Casimir, On the Interaction between Atomic Nuclei and
Electrons, Teyler's Tweede Genootschap, Harlem, 1936.
[2] P. Pyykk"o, E. Pajanne and M. Inokuti, Int.J. Quantum Chem. 7
(1973) 785
[3] L. Evans, P.G.H. Sandars and G.K. Woodgate,
Proc. Roy. Soc. London A 289 (1965) 108.
[4] P. Pyykk"o and M.C. Seth, unpublished results.
%%%%
LINEAR MAGNETIC DICHROISM IN ANGLE-RESOLVED PHOTOEMISSION FROM
CO(0001) AND FE(110) VALENCE BANDS
A. RAMPE, D. Hartmann, M. Reese, and G. G"untherodt
2. Physikalisches Institut, RWTH Aachen, D-52056 Aachen,
Germany
The linear magnetic dichroism in the angular distribution of
photoelectrons (LMDAD) from the valence bands of bulk-type
epitaxial layers of Co(0001) and Fe(110)on W(110) has been
studied by angle-resolved photoemission in the photon energy
range from 14eV to 64eV.
For Co(0001) the LMDAD appears only near the crossing points
of nonrelativistic $\Lambda^3$ and $\Lambda^1$ bands along the
A \Gamma direction of the first Brillouin zone. A simple model
is presented which interprets the LMDAD as follows:
a) Near such a crossing point the states are $\Lambda^1
\Lambda^3$ hybrids induced by the spin-orbit coupling.
b) The photoelectron waves, emitted coherently from
the $\Lambda^1$ and the $\Lambda^3$ part of the hybrid into
a $\Lambda^1$ final state, interfere with a phase difference,
which depends on the direction of the magnetization, thus
causing the LMDAD.
The LMDAD of Fe(110) is interpreted in the framework of this
model. The observed LMDAD can be explained by the formation of
two $\Sigma^{1 \downarrow} \Sigma^{3 \downarrow}$ hybrids from
bands with mainly $\Sigma^{1 \downarrow}$ and
$\Sigma^{3 \downarrow}$ character and two corresponding
$\Sigma^{1 \uparrow} \Sigma^{3 \uparrow}$ hybrids. We found that
a) the LMDAD of the $\Sigma^{1 \downarrow} \Sigma^{3 \downarrow}$
hybrids possesses the opposite sign of the exchange-split
$\Sigma^{1 \uparrow} \Sigma^{3 \uparrow}$ hybrids.
b) The LMDAD-asymmetry of these hybrids shows a strong dependence
on the photon energy with a maximum at about 26.7eV, such that
the LMDAD varies for the same initial states but different
final states.
c) We found no hints for a hybridization between states of
$\Sigma^1$ and $\Sigma^3$ symmetry but different spin
character.
This work has been supported by the DFG / SFB 341
and the BMBF (FKZ: 05 5PCFXB 2)
%%%
IMAGING OF MAGENETIC DOMAINS BY MEANS OF MAGNETIC DICHROISMS:
MAGNETIC SPECTRO-MICROSCOPY
C.M. SCHNEIDER, K. Meinel, J. Kirschner
MPI f. Mikrostrukturphysik, Weinberg, D-06120 Halle
Multi-component thin film systems are of growing interest in
magnetism with respect to both reasearch and application. They
exhibit fascinating effects such as the oscillatory magnetic
exchange coupling and the giant magnetoresistance. In order to
arrive at a better understanding of these magnetic properties and
the contributions from the individual components, an element-
specific characterization is mandatory. This is particulary true
for the magnetic microstructure. We have therefore developed a
technique allowing an element-specific imaging of the magnetic
domains of the different components in thin film systems. The
technique is based on the magnetic circular dichroism (MCD) in the
emission of photo- and secondary electrons, which is observed with
excitation by circularly polarised synchrotron radiation. By tuning
the energy of the radiation to the absorption edges of the
respective material and by using Auger electrons for the imaging,
one yields both elemental selectivity and surface sensitivity,
which is an essential prerequisite for studying thin film systems.
The various contrast mechanisms due to different magneto-dichroic
effects will be discussed, and first applications to the Fe/Cr
system will be shown.
The work was supported by the Bundesministerium f. Forschung u.
Technologie (grants No. 055EFAAI5 and No. 055VHFX1)
%%%
ON THE INTERPRETATION OF MXCD EXPERIMENTS ON ITINERANT MAGNETS
P. STRANGE
Physics Department, University of Keele, Staffs, ST5 5BG
The famous sum rules derived by Thole, Carra, Altarelli and
coworkers have provided a unique insight into localized magnetism
and have enabled us to use absorption dichroism measurements to
make an approximate determination of the orbital and spin con-
tribution to the magnetic moment of a material separately. In this
talk I will present a new rule for comparing absorption dichroism
experiments directly with band theory. We are able to show a direct
proportionality between the dichroism and the total magnetic moment
of the j=l-1/2 electron states above the fermi energy. i.e.
Dichroism experiments enable us to determine the total magnetic
moment of the j=l-1/2 conduction electron states separately from
the total moment of the $j=l+1/2$ states. The new rule does not
require an energy integration and all the required parameters can
be calculated easily from relativistic spin-polarised band theory.
This theory will be illustrated with applications at the $L_2$ edge
in pure Fe and in the random substitutional alloy Fe80Co20.
%%%
MAGNETIC GROUND STATE PROPERTIES AND ANGULAR DEPENDENT MAGNETIC
DICHROISM IN CORE LEVEL PHOTOEMISSION
Gerrit van der Laan
Daresbury Laboratory, Warrington WA4 4AD, United Kingdom
Angle dependent core level photoemission excited with polarized x-
rays can be used to determine the magnetic properties of metallic
systems by separating the geometrical dependence from the physical
information which is contained in the spectra. There are four
different geometries which can be distinguished: magnetic circular
dichroism (MCD), linear dichroism (LD), circular dichroism in the
angular dependence (CDAD), and magnetic linear dichroism in the
angular dependence (MLDAD). The shape of the dichroic spectra in a
one-electron model is determined by the core spin-orbit interaction
and the spin field. A good agreement between experiment and theory
is obtained for the Fe 3p photoemission of iron when the spin and
orbit dependence of the life time broadening is taken into account.
The influence of the orbit field and the spin filtering in the
solid can be estimated from the first spectral moment.
%%%
RELATIVISTIC AES
P. WEINBERGER, L. Szunyogh and J. Redinger
Inst. f"ur Techn. Elektrochemie, TU Wien, Getreidemarkt 9,
A-1060 Wien
Non-spin-polarized and spin-polarized relativistic
core-core-valence (ccv)-
\begin{center}
\fbox{$
\begin{array}{llcl}
\psi _1({\bf r}_1) & \mbox{core state} \# 1 & : & \epsilon _1 \\
\psi _2({\bf r}_2) & \mbox{continuum state} & : & \epsilon _2 \\
\psi _3({\bf r}_3) & \mbox{core state} \# 2 & : & \epsilon _3 \\
\psi _4({\bf r}_4) & \mbox{valence state} & : & \epsilon _4
\end{array}
$}\qquad \fbox{$
\begin{array}{cc}
----- & \epsilon _2 \\
& \\
======= & \epsilon _4 \\
& \\
----- & \epsilon _3 \\
----- & \epsilon _1 \\
\end{array}
$}
\end{center}
and core-valence-valence (cvv) relativistic AES theory
\begin{center}
\fbox{$
\begin{array}{llcl}
\psi _1({\bf r}_1) & \mbox{core state} & : & \epsilon _1 \\
\psi _2({\bf r}_2) & \mbox{continuum state} & : & \epsilon _2 \\
\psi _3({\bf r}_3) & \mbox{valence state} & : & \epsilon _3 \\
\psi _4({\bf r}_4) & \mbox{valence state} & : & \epsilon _4
\end{array}
$}\qquad \fbox{$
\begin{array}{cc}
----- & \epsilon _2 \\
& \\
======= & \epsilon _3, \epsilon _4\\
& \\
& \\
----- & \epsilon _1 \\
\end{array}
$}
\end{center}
as based on local spin density functional approximations is discussed for
semi-infinite solid systems, i. e. , for systems with surfaces. It will
be shown that the selection rules are in general governed by the
following scheme:
\begin{center}
\fbox{$
\begin{array}{ccccccc}
& & \mbox{{\bf Degeneracy}} & & {\bf D}^2 & {\bf E}^2 & {\bf DE} \\ &
\begin{array}{c}
\mbox{Core WF} \\ \psi _1({\bf r},\epsilon _1)
\end{array}
&
\begin{array}{c}
\mbox{Core WF} \\ \psi _3({\bf r},\epsilon _3)
\end{array}
&
\begin{array}{c}
\mbox{Cont WF} \\ \psi _2({\bf r},\epsilon _2)
\end{array}
& & & \\
& & \mbox{\ } & & & & \\
\mbox{no magnetic field} & \mu _1 & \mu _3 & \mu _2 & 3j & 3j & 6j \\
\mbox{with magnetic field} & - & - & - & 9j & 9j & 12j
\end{array}
$}
\end{center}
and that the intensity can be expressed as
$$
\overline{P}=\sum\limits_n\exp (-\gamma d_n){\overline{P}}^n\quad ,
$$
where the ${\overline{P}}^n$ are layer-dependent transition
probabilities, $d_n$ the separation between the layers and $\gamma $
is proportional to an escape length. \\
%%%
MAGNETO OPTICAL KERR EFFECT IN STRONGLY ANISOTROPIC MAGNETIC THIN
FILMS: FEPT AND CO
D. WELLER
IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120
Magneto-optical (MO) effects both in the visible and in the x-ray
regime are powerful experimental methods to study magnetic and
electronic properties of thin film materials as are being used in
magnetic and magneto-optic recording. Of the various important
materials parameters we have specifically investigated the
electronic underpinnings of the magneto-optical Kerr effect (MOKE),
which is used in MO recording to read back the stored bit
information. In model systems like epitaxial Co and FePt super-
lattice films grown in different crystallographic orientations, we
demonstrate that there exists a strong correlation between the
magnitude of MOKE and the occurrence of magneto-crystalline
anisotropy (MCA). Up to 100% changes in Kerr rotation and
ellipticity are observed, as the orientation is changed from (001)
to (110) in FePt (CuAu(I)) compound films. While the (001) film has
a strong out-of-plane anisotropy with anisotropy fields of the
order of $\sim$80 kOe, the (110) film has an in-plane easy axis with
anisotropy of similar strength and large coercivity of H$_C \sim$
7 kOe, which makes this an interesting material for magnetic
recording applications. The observed Kerr effect enhancement occurs
in the (001) direction, that means for the case of a parallel
alignment of photon propagation and MCA axis.
work done with G.R. Harp, A. Cebollada, A. Carl and
R.F.C. Farrow; see D. Weller et al., Phys. Rev. Lett. 72, 2097 (1994).
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MAIN RESEARCH INTERESTS
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BELGIUM
1) Michel Godefroid
CANADA
2) S.P. Goldman
3) Vedene H. Smith,Jr.
DENMARK
4) Gustavo Adolfo Aucar <09a02gaa@arunne.bitnet>
5) Jens Peder Dahl
6) Hans J\o rgen Aa. Jensen
7) Jens Oddershede
8) Sten Rettrup
9) Stephan P.A. Sauer
ESTONIA
10) Uko Maran
FINLAND
11) Tapio T. Rantala
12) Dage Sundholm
FRANCE
13) P. Braunstein
14) H. Chermette
15) Chantal Daniel
16) J. P. Desclaux
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18) Jean-Louis Heully
19) Paul INDELICATO
20) Michel Pelissier
21) Marie-Madeleine ROHMER
22) Christian Teichteil
23) Alain Veillard
GERMANY
24) Aleksey B. Alekseyev
25) Dirk Andrae
26) John BANHART
27) Robert J. Buenker
28) Klaus Capelle
29) Michelle Carnell
30) Christian Chang
31) Geerd H. F. Diercksen
32) Klaus Dietz
33) Michael Dolg
34) Reiner Dreizler
35) Hubert Ebert
36) Roland Feder
37) Gregor-Martin Fehrenbach
38) Burkhard Fricke
39) Lothar Fritsche
40) Norbert Geipel
41) Walter Greiner
42) E.K.U. Gross
43) Christoph Heinemann
44) J\"urgen Hinze
45) Siegfried Huebener
46) Martin Kaupp
47) Stefan Keller
48) Dietmar Kolb
49) Karl Klinkhammer
50) J. Hrusak
51) J. V. Kratz
52) J. K\"ubler
53) W. Kutzelnigg
54) J. Ladik
55) M. Mahnig
56) Christel M. Marian
57) Franz Mark
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61) Edgar Ottschofski
62) Valeria Pershina
63) S.D. Peyerimhoff
64) H. Pilkuhn
65) Bernd Reichert
66) Manuel Richter
67) Notker R\"osch
68) Matthias Schaedel
69) Werner Scheid
70) Paul von Ragu\'e Schleyer
71) Hans-Georg von Schnering
72) Hubert Schmidbaur
73) W.H.Eugen Schwarz
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75) Hermann Stoll
76) Detlev Suelzle
77) Birgit Willerding
78) G\"unter Wunner
GREECE
79) P. Marketos
HUNGARY
80) Laszlo Nyulaszi
ISRAEL
81) Uzi Kaldor
ITALY
82) Maurizio Casarin
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93) Robert A. de Groot
94) Bert de Jong
95) E. van Lenthe
96) Joop van Lenthe
97) Hirzo Merenga
98) Wim Nieuwpoort
99) Jaap G. Snijders
100) Luuk Visscher
101) Svetlana Kotochigova
NEW ZEALAND
102) Peter Schwerdtfeger
NORWAY
103) Odd Gropen
104) Jon K. Laerdahl
105) Inge Roeggen
106) Trond Saue
OESTERREICH
107) Dieter Gruber
108) Robert Polly
POLAND
109) Maria Barysz
110) Jacek Bieron
111) Zdzislaw LATAJKA
112) Andrzej Wojciech Rutkowski
113) Jacek Migdalek
114) Barbara Nissen-Sobocinska
115) J'ozef Eugeniusz Sienkiewicz
116) Maria Stanek
117) Radoslaw Szmytkowski
PORTUGAL
118) Jose Manuel Pires Marques
RUSSIA
119) Titov Anatoli
120) Alexander A. BAGATUR'YANTS
121) Ulyana I. Safronova
122) Vladimir Shabaev
123) V.L. Yakontov <\"m1s2s::yakhontov\"@cosmo.physi.uni-heidelberg.de>
SLOVAKIA
124) Vladimir Kelloe
125) Martina BITTEREROVA
126) Miroslav Urban
SOUTH KOREA
127) Yoon Sup Lee
SPAIN
128) Inmaculada Martin
129) Luis Seijo
SWEDEN
130) Lars A. Bengtsson
131) Stephan Fritzsche
132) Sven Larsson
133) Boris Minaev
134) Jeppe Olsen
135) Ann-Marie M\aa rtensson-Pendrill
136) Arne Ros\'en
137) Andrzej J. Sadlej
138) Per Svensson
139) Ulf Wahlgren
SWITZERLAND
140) Helmut Sigel
141) Walter Thiel
UNITED KINGDOM
142) G. Y. Guo
143) Richard E. Moss
144) A. M. Simper
BNFL Company Research Laboratory
Springfield Works Salwick
Preston PR4 OXJ
145) Stephen Wilson
USA
146) Kenneth George Dyall
147) Walter C. Ermler
148) Charlotte Froese Fischer
149) Yasuyuki Ishikawa
150) Ajaya K. Mohanty
151) Farid A. Parpia
STEERING COMMITTEE
152) E.J. Baerends
153) J.P. Daudey
154) Knut Faegri
155) Ian P. Grant
156) Bernd Artur He\ss
157) J. Karwowski
158) Pekka Pyykk\"o
159) Karlheinz Schwarz
160) A. Sgamelotti
161) Dr. Hans Karow
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End of REHE Newsletter No. 13