Physics of Spin in Solids: Materials, Methods and Applications NATO Science Series A Series presenting the results of scientific meetings supported under the NATO Science Programme The Series is published by IOS Press, Amsterdam, and Kluwer Academic Publishers in conjunction with the NATO Scientific Affairs Division Sub-Series I II III IV V Life and Behavioural Sciences Mathematics, Physics and Chemistry Computer and Systems Science Earth and Environmental Sciences Science and Technology Policy IOS Press Kluwer Academic Publishers IOS Press Kluwer Academic Publishers IOS Press The NATO Science Series continues the series of books published formerly as the NATO ASI Series The NATO Science Programme offers support for collaboration in civil science between scientists of countries of the Euro-Atlantic Partnership Council The types of scientific meeting generally supported are “Advanced Study Institutes” and “Advanced Research Workshops”, although other types of meeting are supported from time to time The NATO Science Series collects together the results of these meetings The meetings are co-organized bij scientists from NATO countries and scientists from NATO’s Partner countries – countries of the CIS and Central and Eastern Europe Advanced Study Institutes are high-level tutorial courses offering in-depth study of latest advances in a field Advanced Research Workshops are expert meetings aimed at critical assessment of a field, and identification of directions for future action As a consequence of the restructuring of the NATO Science Programme in 1999, the NATO Science Series has been re-organised and there are currently Five Sub-series as noted above Please consult the following web sites for information on previous volumes published in the Series, as well as details of earlier Sub-series http://www.nato.int/science http://www.wkap.nl http://www.iospress.nl http://www.wtv-books.de/nato-pco.htm Series II: Mathematics, Physics and Chemistry – Vol 156 Physics of Spin in Solids: Materials, Methods and Applications edited by Samed Halilov Naval Research Laboratory, Washington, DC and University of Pennsylvania, Philadelphia, U.S.A KLUWER ACADEMIC PUBLISHERS NEW YORK, BOSTON, DORDRECHT, LONDON, MOSCOW eBook ISBN: Print ISBN: 1-4020-2708-7 1-4020-2225-5 ©2005 Springer Science + Business Media, Inc Print ©2004 Kluwer Academic Publishers Dordrecht All rights reserved No part of this eBook may be reproduced or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, without written consent from the Publisher Created in the United States of America Visit Springer's eBookstore at: and the Springer Global Website Online at: http://ebooks.kluweronline.com http://www.springeronline.com Contents Contributing Authors Preface ix xv Acknowledgments xvii Fulde-Ferrell-Larkin-Ovchinnikov-like state in Ferromagnet Superconductor Proximity System B L Gy¨ orffy, M Krawiec, J F Annett 1.1 Introduction 1.2 Model and theory 1.3 Andreev bound states 1.4 Spontaneous current 1.5 Transport properties 1.6 2D FFLO state 1.7 Conclusions Acknowledgments 11 14 14 15 References 15 Exchange Force Image of Magnetic Surfaces Hiroyoshi Momida, Tamio Oguchi 2.1 Introduction 2.2 Models and Methods 2.3 Results and Discussion 2.4 Conclusions Acknowledgments 17 References 24 Spin-dependent Tunnel Currents for Metals or Superconductors with Charge-Density Waves A M Gabovich, A I Voitenko, Mai Suan Li, H Szymczak, M Pekala 3.1 Introduction 3.2 Formulation 3.3 Results and discussion 17 18 19 23 23 25 25 27 32 Acknowledgments 38 References 38 v vi Contents Electronic Structure of Strongly Correlated Materials: towards a First Principles Scheme Silke Biermann, Ferdi Aryasetiawan, Antoine Georges 4.1 The parent theories 4.2 The Ψ-functional 4.3 GW+DMFT 4.4 Challenges and open questions 4.5 Static implementation 4.6 Perspectives 4.7 Acknowledgments 45 52 54 59 61 63 64 References 64 43 Spin-density Wave and Short-range Oscillations in Photoemission from Films of Cr Metal S.L Molodtsov 5.1 Incommensurate spin-density wave 5.2 Short-range oscillations 5.3 Acknowledgments 70 77 82 References 82 67 The Role of Hydration and Magnetic Fluctuations in the Superconducting Cobaltate M.D Johannes, D.J Singh 6.1 Hydrated and Unhydrated Band Structures 6.2 Quantum Critical Fluctuations 88 91 Acknowledgments 96 References 97 85 Holstein-Primakoff Representation for Strongly Correlated Electron Systems Siyavush Azakov 7.1 Introduction 7.2 Representations of the spl(2.1) algebra 7.3 Slave particles Holstein-Primakoff representation 7.4 Supercoherent States for spl(2.1) Superalgebra 7.5 Discussion and Conclusions Acknowledgments 101 105 108 110 113 113 References 114 Tuning the magnetism of ordered and disordered strongly-correlated electron nanoclusters Nicholas Kioussis, Yan Luo, and Claudio Verdozzi 8.1 Introduction 8.2 Methodology 8.3 Results and discussion 8.4 Conclusions 101 115 115 118 121 136 Contents vii Acknowledgments 137 References 137 Density Functional Calculations near Ferromagnetic Quantum Critical Points I.I Mazin, D.J Singh and A Aguayo 9.1 Introduction 9.2 The LDA Description Near a FQCP 9.3 “Beyond-LDA” Critical Fluctuations 9.4 Ni3 Al and Ni3 Ga 9.5 Towards a Fully First Principles Theory 9.6 Summary and Open Questions 139 140 142 145 149 152 Acknowledgments 152 References 152 139 Interplay between Helicoidal Magnetic Ordering and Superconductivity on the Differential Conductance in HoNi2 B2 C/Ag Junctions I N Askerzade 10.1 Introduction 10.2 Basic Equations 10.3 Results and Discussions 155 156 158 References 159 155 Ab initio Calculations of the Optical and Magneto-Optical Properties of Moderately Correlated Systems: accounting for Correlation Effects 161 A Perlov, S Chadov, H Ebert, L Chioncel, A Lichtenstein, M Katsnelson 11.1 Introduction 161 11.2 Green’s function calculations of the conductivity tensor 164 11.3 Results and discussion 170 11.4 Conclusion and outlook 174 References 174 Spin-dependent Transport in Phase-Separated Manganites 177 K I Kugel, A L Rakhmanov, A O Sboychakov , M Yu Kagan, I V Brodsky, A V Klaptsov 12.1 Introduction 177 12.2 Resistivity 179 12.3 Magnetoresistance 184 12.4 Magnetic susceptibility 188 12.5 Discussion 190 Acknowledgments 193 References 194 New Magnetic Semiconductors on the Base of TlBV I -MeBV I Systems 195 E M Kerimova, S N Mustafaeva, A I Jabbarly, G Sultanov, A.I Gasanov, R N Kerimov viii Contents References 205 Localized Magnetic Polaritons in the Magnetic Superlattice with Magnetic Impurity R.T Tagiyeva Acknowledgments 215 References 215 Spin Stability and Low-Lying Excitations in Sr2 RuO4 S V Halilov, D J Singh, A Y Perlov 15.1 Introduction 15.2 LSDA magnetic ground state 15.3 Formation of spin and orbital moments and pressure dependencies 15.4 Anisotropy of static magnetic susceptibility 15.5 Summary: possible magnetic low-lying excitations and impact upon superconductivity 217 207 217 220 226 236 239 Acknowledgments 241 References 241 Contributing Authors B L Gy¨ orffy, H H Wills Physics Laboratory, University of Bristol, Tyndall Ave., Bristol BS8 1TL, UK Centre for Computational Materials Science, TU Wien, Gertreidemarkt 9/134, A-1060 Wien,Austria M Krawiec, Institute of Physics and Nanotechnology Center, Maria Curie-Sklodowska University, Pl Marii Curie-Sklodowskiej 1, 20-031 Lublin, Poland J F Annett, H H Wills Physics Laboratory, University of Bristol, Tyndall Ave., Bristol BS8 1TL, UK Hiroyoshi Momida, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan Tamio Oguchi, ADSM, Hiroshima University 1-3-1 Kagamiyama, Higashihiroshima 739-8530 Japan A M Gabovich, Institute of Physics, prospekt Nauki 46, 03028 Kiev28, Ukraine A I Voitenko, Institute of Physics, prospekt Nauki 46, 03028 Kiev-28, Ukraine Mai Suan Li, Institute of Physics, Al Lotnikow 32/46, PL-02-668 Warsaw, Poland ix x Contributing Authors H Szymczak, Institute of Physics, Al Lotnikow 32/46, PL-02-668 Warsaw, Poland M Pekala, Department of Chemistry, University of Warsaw, Al Zwirki i Wigury 101, PL-02-089 Warsaw, Poland Silke Biermann, Centre de Physique Theorique, Ecole Polytechnique, 91128 Palaiseau, France Ferdi Aryasetiawan, Research Institute for Computational Sciences, AIST, 1-1-1 Umezono, Tsukuba Central 2, Ibaraki 305-8568, Japan Antoine Georges, Centre de Physique Theorique, Ecole Polytechnique, 91128 Palaiseau, France S.L Molodtsov, Institut fr Festkrperphysik, Technische Universitt Dresden, D-01062 Dresden, Germany M.D Johannes, Center for Computational Material Science Naval Research Laboratory Washington, D.C 20375 Siyavush Azakov, Institute of Physics, Azerbaijan Academy of Sciences, Baku-370143, Azerbaijan Nicholas Kioussis, Department of Physics California State University Northridge, California 91330-8268 Yan Luo, Department of Physics California State University Northridge, California 91330-8268 Claudio Verdozzi, Department of Physics California State University Northridge, California 91330-8268 F M Grosche, Department of Physics Royal Holloway, University of London, Egham, UK 230 Spin Stability and Low-Lying Excitations in Sr2 RuO4 contrast, U becomes smaller under positive pressure due to an increase in Coulomb screening, which leads to a magnetization collapse with only a 3% reduction of the lattice constant The spin moment formation condition given by Eq (7) at the same time reads (U + J)ηiσ (EF ) ∼ 1.65 since of ηiσ (EF ) ≈ 0.65 st/eV/spin, which is large enough to satisfy the condition given by Eq (7) and the exchange splitting if not the effects of quantum fluctuations Formation of a local orbital moment requires, along with the spin moment formation, a certain local symmetry imposed by electrostatic crystal fields and relativistic coupling between spin and orbital moments The latter is always present in relativistic considerations, whereas the crystal-field effect has to be strong enough in order for the Hartree fields Ei+ for the two orbitally degenerate states to differ The origin of the orbital polarization can easily be traced out in terms of double-group symmetry classification for irreducible representation Notice that by non-relativistic consideration the basis orbitals have the following spin-angular part i ˆs , | φ1s ∼ √ (Y2,+1 + Y2,−1 )χ | φ2s ∼ √ (Y2,+1 − Y2,−1 )χ ˆs , with χ ˆ as the Pauli spinors, which leads to vanishing orbital momentum ˆ z Ylm = mYlm and orbital degeneracy 1s = 2s Eigenvalues because of L n=1,2s(k) in the periodic crystal will have similar degeneracy In the ˆ so, presence of spin-orbit coupling h the degeneracy in general will be lifted everywhere except perhaps at some high-symmetry points in the Brillouin zone By construction of single-particle eigenvectors from Bloch combinations of the orbitals, the respective eigenvalues can in lowest perturbation order, easily be shown to be split at every k-point ¯ns(k) = (+) +s (−) + ξ2, (9) where the spin-orbit coupling parameter ξ =| ψ1slz ψ2s | + | ψ1+ l+ ψ2− |2 , and (+) , (−) stand for half-sum and half-difference of the non-relativistic bands ns, respectively Thus, electrostatic crystal fields and the spinorbit coupling split the energy levels ¯ns ≈ + s | ξ | (10) at general k-point, with s = ± (not a spin index anymore) and ξ = φ1sˆlz φ2s since ˆl± is vanishing on the Ru sites The corresponding Formation of spin and orbital moments and pressure dependencies 231 eigenvectors in the lowest order of perturbation theory are | kns = is αns (k) | φis , (11) is which for the angular part implies | k1s ∼ Y2,+1 χ ˆs , ˆs , | k2s ∼ Y2,−1 χ since αis is either one or zero if no magnetic field or exchange splitting is present More formally this result could be obtained within doublegroup classification when the wave function is to be expanded in terms of basic functions corresponding to ∆56 and ∆57 irreducible representations of C4v group [22] By expanding the field operators in terms of the is-orbitals ψˆ = is ˆns(k), one easily verifies that the projection of ns,is αns (k) | kis c ˆ ζ≡e ˆζ ψˆ | l | ψˆ along spin quantization the net orbital momentum L ˆζ will be different from zero only if the spin degeneracy of direction e each state is lifted Then, in the lowest order of the perturbation theory in spin-orbit coupling [23–25] ˆ L ζ ≈ −4ξ ˆζ ( L ≡e ˆζ l | 2σ 3σ | σl | 4σ A(12, 34, σσ) 1σ | e 1234,σ + − + L ), (12) where the matrix element A(12, 34, σσ ) ≡