216 Pages·1987·6.402 MB·English

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23 ...., . .r -n.::lllll"!!!!!!. Procee Managing Editor: H. K. V. Lotsch Volume 1 Fluctuations and Sensitivity in Nonequilibrium Systems Editors: W. Horsthemke and D. K Kondepudi Volume 2 EXAFS and Near Edge Structure 11/ Editors: K O. Hodgson, B. Hedman, and J. E. Penner-Hahn Volume 3 Nonlinear Phenomena in Physics Editor: F. Claro Volume 4 Time-Resolved Vibrational Spectroscopy Editors: A. Laubereau and M. Stockburger Volume 5 Physics of Finely Divided Matter Editors: N. Boeeara and M. Daoud Volume 6 Aerogels Editor: J. Fricke Volume 7 Nonlinear Optics: Materials and Devices Editors: C. Flytzanis and J. L. Oudar Volume 8 Optical Bistability 11/ Editors: H. M. Gibbs, P. Mandel, N.Peyghambarian, and S.D.Smith Volume 9 Ion Formation from Organic Solids (IFOS 11/) Editor: A. Benninghoven Volume 10 Atomic Transport and Defects in Metals by Neutron Scattering Editors: C.Janot, W.Petry, D.Riehter, and T.Springer Volume 11 Biophysical Effects of Steady Magnetic Fields Editors: G. Maret, J. Kiepenheuer, and N. Boeeara Volume 12 Quantum Optics IV Editors: J. D. Harvey and D. F. Walls Volume 13 The Physics and Fabrication of Microstructures and Microdevices Editors: M.J. Kelly and C. Weisbueh Volume 14 Magnetic Properties of Low-Dimensional Systems Editors: L. M. Falieov and J. L. Moran-L6pez Volume 15 Gas Flow and Chemical Lasers Editor: S. Rosenwaks Volume 16 Photons and Continuum States of Atoms and Molecules Editors: N.KRahman, C.Guidotti, and M.Allegrini Volume 17 Quantum Aspects of Molecular Motions in Solids Editors: A Heidemann, A Magerl, M.Prager, D.Riehter, and T.Springer Volume 18 Electro-optic and Photorefractive Materials Editor: P. GOnter Volume 19 Lasers and Synergetics Editors: R. Graham and A. Wunderlin Volume 20 Primary Processes in Photobiology Editor: T. Kobayashi Volume 21 Physics of Amphiphilic Layers Editors: J. Meunier, D. Langevin, and N. Boeeara Volume 22 Semiconductor Interfaces: Formation and Properties Editors: G. Le Lay, J. Derrien, and N. Boeeara Volume 23 Magnetic Excitations and Fluctuations 1/ Editors: U. Balueani, S. W. Lovesey, M.G. Rasetti, and V. Tognetti Springer Proceedings in Physics is a new series dedicated to the publication of conference proceedings. Each volume is produced on the basis of camera-ready manuscripts prepared by conference contributors. In this way, publication can be achieved very soon after the conference and costs are kept low; the quality of visual presentation is, nevertheless, very high. We believe that such a series is preferable to the method of publishing conference proceedings in journals, where the typesetting requires time" and considerable expense, and results in a longer publication period. Springer Proceedings in Physics can be considered as a journal in every other way: it should be cited in publications of research papers as Springer Proc. Phys., followed by the respective volume number, page number and year. Magnetic Excitations and Fluctuations II Proceedings of an International Workshop, Turin, Italy, May 25 - 30, 1987 Editors: U. Balucani, S. W Lovesey, M. G. Rasetti, and V. Tognetti With 96 Figures Springer-Verlag Berlin Heidelberg New York London Paris Tokyo Dr. Umberto Balucani Istituto di Elettronica, Quantistica, CNR, via Panciatichi 56/30. 1-50127 Firenze, Italy w. Professor Stephen Lovesey Rutherford Appleton Lab., Chilton, Oxfordshire, OX 11 OQX, U.K. Professor Mario G. Rasetti Dipartimento di Fisica Politecnico di Torino, Corso Duca degli Abruzzi, 24, 1-10129 Torino, Italy Professor Valerio Tognetti Dipartimento di Fisica, Universita di Firenze, Largo E. Fermi, 1-50125 Firenze, Italy ISBN-13: 978-3-642-73109-9 e-ISBN-13: 978-3-642-73107-5 001: 10.1007/978-3-642-73107-5 Library of Congress Cataloging-in-Publication Data. Magnetic excitations and fluctuations II: pro ceedings of an international workshop, Turin, Italy, May 25-30, 1987 / editors, U. Balucani ... let al.l. (Springer proceedings in physics; v. 23) Sponsored by the Institute for Scientific Interchange (lSI) In cludes index. 1. Statistical mechanics - Congresses. 2. Mathematical physics - Congresses. 3. Spin excitations - Congresses. I. Balucani, U. (Umberto), 1942-. II. Institute for Scientific Interchange. III. Series. QC174.7M34 1987 539.7'2-dc19 87-28852 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, speCifically the rights of translation, reprinting, reuse of illustrations, reCitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks. Duplication ofthis publication or parts thereof is only permitted under the provisions of the German Copyright Law of September 9, 1965, in its version of June 24, 1985, and a copyright fee must always be paid. Violations fall underthe prosecution act of the German Copyright Law. © Springer-Verlag Berlin Heidelberg 1987 Softcover reprint of the hardcover 1s t edition 1987 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and there fore free for general use. 2153/3150-543210 Preface An international workshop on Elementary Excitations and Fluctuations in Magnetic Systems was held in Turin for five days beginning 25 May, 1987. The workshop followed much the same format as the one with the same title held in San Miniato in 1984 (proceedings: Springer Series in-Solid-State Sciences, Vol. 54), that most participants contributed talks and provided papers for the proceedings. While many of the participants had attended the first workshop, 15 of the 40 invited review papers were presented by scientists who had not. The majority of the talks reported theoretical work concerned with the introduction of new techniques. However, experimental work was also well represented, not least because many of the reported theoretical studies were motivated by experimental findings, and a highlight of the workshop was an extremely stimulating session devoted to recent neutron scattering measure ments, on various systems, that exploited polarization analysis. The fine venue of the workshop, Villa Gualino, with its excellent facili ties and spacious accommodation, helped to produce a delightful relaxed and friendly atmosphere. For the use of Villa Gualino and significant financial support we are indebted to our host organization, the Institute for Scien tific Interchange (lSI). Additional financial support came from the Consiglio Nazionale delle Ricerche (CNR), Centro Interuniversitario di Struttura della Material del Ministero della Pubblica Istruzione (CISM-MPI) and Gruppo Nazionale di Struttura della Materia (GNSM-CNR). The permanent staff of the lSI, Tiziana Bertoletti (Coordinator) and Car men Novella (Secretary) took on the lion's share of the administration and organization of the workshop. Preparation of the proceedings for publica tion was competently and swiftly handled by Carla Pardini (Florence). The creature comforts of good food, a good bar service and well-prepared ac commodation were provided, with much charm, by Lina De Nisco and her helpers. Finally, we thank all the participants for their attendance and spirited individual contributions to the success of the workshop. Turin, June 1987 U. BaJucam S. W. Lovesey M. Rasetti V. Tognetti v Contents Part I Statistical Mechanics and Mathematical Physics Statistical Mechanics of the Integrable Models By R.K. Bullough, D.J. Pilling, and J. Timonen 2 Lattice Equations, Hierarchies and Hamiltonian Structures By H. W. Capel and G.L. Wiersma ............ . . . . . . . . . . . . . 6 Modular Invariance and Two-Dimensional Critical Systems By C. Itzykson ....................................... 11 Variational Principle for Quantum Effects on Nearly Sine-Gordon Chains. By R. Giachetti and V. Tognetti (With 2 Figures) ....... 15 Quantum Theory of Planar Kinks in a Finite Easy Plane Ferromagnetic Chain. By J.F. Lemmens and W.J.M. de Jonge .... 20 RAF Model and Solid Oxygen: Infinite Degeneracy, Soft Lines, No LRO in Classical Approximation and Order by Quantum Disorder By E. Rastelli and A. Tassi (With 2 Figures) ................ 25 Phase Transitions in Ising Superlattices By D. W. Hone (With 2 Figures) .......................... 29 A Fermionic Treatment of the Frustrated Ising Model By J.A. Blackman and J. Poulter (With 3 Figures) . . . . . . . . . . . . . 34 Calculation of Static Magnetic Susceptibilities of a Jahn-Teller E- Doublet By P. de Vries, A. Lagendijk, and H. De Raedt (With 1 Figure) 38 Part II Random Field Problems, Spin Glasses and Chaotic Behaviour . Critical Properties of the Random Field Ising Model By J. Villain, T. Nattermann, and M. Schwartz ............... 44 Random-Exchange and Random-Field xv-Chain for 8=1/2 By T. Schneider and A. Politi (With 2 Figures) ............... 49 VII Spin-glass-like Behaviour in Spinels By E. Agostinelli and D. Fiorani (With 4 Figures) 55 Harmonic Magnons in Spin Glasses: Cdo.35MnO.65 Te By D.L. Huber, W.Y. Ching, and T.M. Giebultowicz (With 2 Figures) ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 On a Symmetric (2S+1)-State System Coupled to Its Environment: Tunneling Splitting and Quantum Coherence. By T. Tsuzuki ..... 65 Regular and Chaotic Dynamics of Classical Spin Systems By N. Srivastava, C. Kaufman, G. Miiller, R. Weber, and H. Thomas (With 3 Figures) ................................. . . . . . 70 The Kicked Quantum Spin: A Model System for Quantum Chaos By H.J. Mikeska and H. Frahm (With 1 Figure) ............... 75 Chaotic Dynamics of Spin Wave Instabilities By S.M. Rezende, F.M. de Aguiar, and A. Azevedo (With 3 Figures) 79 Part III Theory of Spin Excitations Spin 1 vs Spin 1/2 Antiferromagnetic Chains: The Staggered Magnetization By D.C. Mattis and C.Y. Pan (With 3 Figures) ............... 88 Excitations and Critical Behavior in Generalized Heisenberg Spin Chains By J.C. Bonner, G. Milller, and J.B. Parkinson (With 3 Figures) 95 Exact Results for the Out of Plane Dynamical Correlation Function in a Classical Easy Plane Ferromagnet at Low Temperatures By G. Reiter (With 2 Figures) ............................ 101 A Comparison of the Bethe Ansatz and Green FUnction Approaches to Two-Magnon States of the Ferromagnetic Chain By P.D. Lolyand W.K. Scott (With 1 Figure) ................ 105 Nonlinear Effects in Low-Dimensional Magnetism: Solitons and Vortices. By A.R. Bishop, C. Kawabata, F.G. Mertens, and G.M. Wysin (With 1 Figure) ......................... 109 Theory of Excitations in Incommensurably Modulated Magnets By P.-A. Lindgard (With 2 Figures) ....................... 114 Linear Spin Dynamics of Incommensurably Modulated Magnets: Numerical and Analytic Results By S. W. Lovesey and A.P. Megann (With 3 Figures) ........... 120 On the Interpretation of Electronic and Phonon Anomalies in Mixed Valence Compounds. By A. Stasch ........................ 125 VIII Bloch Lines as Magnetic Excitations in Domain Wall Dynamics with a Large Sensitivity to Initial Conditions By J.J. Zebrowski and A. Sukiennicki (With 3 Figures) ......... 130 Dynamics of Magnetic Domain Walls and Barkhausen Noise in Metallic Ferromagnetic Systems. By G. Berlotti . . . . . . . . . . . . . .. 135 Part IV Spin Excitations: Experiments and Computer Simulations Magnetic Fluctuations and Excitations in the 8=1 Antiferromagnetic Chains of NENP. By L.P. Regnault, W.A.C. Erkelens, J. Rossat Mignod, J.P. Renard, M. Verdaguer, W.G. Stirling, and C. Vettier (With 5 Figures) .................................. ~ . .. 142 Study of Longitudinal Fluctuations in CsNiFs by Means of Inelastic Polarized Neutron Scattering. By U. Balucani, B. Dorner, K. Kakurai, R. Pynn, M. Steiner, V. Tognetti, and R. Vaia (With 4 Figures) ... 147 Dynamics of Critical Fluctuations in Isotropic Ferromagnets: Current Problems. By F. Mezei (With 2 Figures) .................... 152 Magnetism of MnSi and FeSi. By G. Shirane (With 5 Figures) .... 157 Neutron Scattering from Heavy Fermion Systems. By C. Broholm, J.K. Kjems, G. Aeppli, E. Bucher, and W.J.L. Buyers (With 3 Figures) ...................................... 162 Linear and Nonlinear Excitations in the 8=1/2 Ferromagnetic Chain System [C6Hn NHS]CuBrS (CHAB) By K. Kopinga and W.J.M. de Jonge (With 3 Figures) .......... 166 Doublings of Soliton Modes and Soliton Magnetic Resonance (SMR) By J.P. Boucher (With 10 Figures) ........................ 171 Relaxation Phenomena in Non-linear Systems; A Mossbauer Effect Spectroscopy and Susceptibility Study. By M. EIMassalami, H.H.A. Smit, H.J.M. de Groot, R.C. Thiel, and L.J. de Jongh (With 8 Figures) ...................................... 178 A Raman Scattering Study of the Spin-Phonon Interaction in Rutile Structure Antiferromagnets By D.J. Lockwood and M.G. Cottam (With 3 Figures) .......... 186 Raman Scattering Studies of Optical Magnons and of High-Energy Magnetic Excitons By P. Moch, A.T. Abdalian, and B. Briat (With 3 Figures) ...... 191 Spin-Dynamics Studies of Excitations in xv-Chains By D.P. Landau, R.W. Gerling, and M.S.S. Challa (With 3 Figures) 196 IX NUmerical Transfer-Kernel Results for the Classical xy-Chain in a Magnetic Field By R. W. Gerling, T. Delica, and H. Leschke (With 2 Figures) 199 Monte Carlo Simulation of the Quantum Sine-Gordon Chain By S. Wouters and H. De Raedt (With 2 Figures) .............. 204 Index of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . .. 209 *L ecturers , names are printed in italics. x Part I Statistical Mechanics and Mathematical Physics

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