An international workshop on Elementary Excitations and Fluctuations in Magnetic Systems was held in San Miniato, Italy, for five days beginning 28 May, 1984. The workshop comprised eight working sessions that contai ned a total of 43 invited talks, and 58 scientists were in attendance from 14 countries. Our aim was to review some topics of current interest in the statistical physics of magnetic materials and models, with an emphasis on theoretical studies and confrontations between these and experimental and computer simulation data. book contains summary papers written by the invited speakers, and This the material will be of immediate interest to graduate students and resear chers engaged in studies of magnetic properties. There is, perhaps, no ef fective way to record and convey the benefit of the numerous discussions between the participants that are a significant integral feature of a work shop. The magnificent .venue of the workshop, I Cappuccini, was made availa ble to us by the.Cassa di Risparmio San Miniato. Financial support for the workshop was received from Consiglio Nazionale delle Ricerche, Universita degli Studi di Firenze and the Gruppo Nazionale Struttura,della Materia. Our administrative load and the burden of preparing the proceedings for publication was made light by the talents of Carla Pardini (CNR, Florence), and Caroline Monypenny and Jane Warren (Rutherford Appleton Laboratory). Fina 11y, we wish to thank all the participants for their attendance and individual contributions to the success of the workshop.

Inhalt
I Experimental Studies of One-Dimensional Magnets.- Specific Heat of TMMC due to Non-Linear Excitations: Comparison with Classical Models.- Narrow and Broad Solitons in the Antiferromagnetic Chains of CsCoCl3 and TMMC.- Spin Waves in a One-Dimensional Antiferromagnetic Insulator.- Solitons in a XY (S=1/2) Quantum System.- Mössbauer Relaxation Studies of ?-Domain-Wall Dynamics in Pure and Impure Ising-Type Magnetic Chains.- k=0 Excitations in the Quantum Chain Systems (C6H11NH3)CuCl3 and (C6H11NH3)CuBr3.- Magnon-Phonon Coupling in Spin-½ Quasi 1D Antiferromagnets.- Spin Dynamics in CsNiF3: Spinwaves, 2-Spinwaves, Solitons.- II Spin Wave Dynamics in One Dimension.- Classical Ferromagnetic Chain in a Field; Spin-Waves Versus Non- Perturbative Interactions.- The Life Time of the Spin Waves of a Classical Ferromagnetic Chain in an Applied Magnetic Field.- Quantum Spin Chains: Phase Behaviour and Dynamic Excitations.- Nonlinear Excitations in the Classical XY-Model.- Field Dependent Spin Dynamics of Antiferromagnetic Heisenberg Chains.- Is CsNiF3 a Classical System?.- Spin Wave Theory for the Classical Easy Plane Ferromagnet in Zero Field: Exact Results at Low Temperature.- III Soliton Theories.- Sine-Gordon Statistical Mechanics.- Solitons in Lattice Systems.- Thermodynamics and Correlation Functions of Non-Linear Excitations in the Easy-Plane Ferromagnetic Chain.- Is TMMC a Sine-Gordon System?.- Dynamics of Phase Transitions in Ferromagnetic Domain-Wall Structures.- IV Mixed and Disordered Magnets.- Stress Fluctuations and Local Structural Distortions in Ferromagnetic Metallic Glasses: Their Role on the Relaxation of the Magnetic Permeability.- Frustration on Fractals.- A Weakly Anisotropic Ising Model in a Random Field.- Spin Dynamics Associated with Local Magnons inFeF2: Mn.- 2D Pure and Dilute Quantum Transverse Ising Model.- The Random Eield Ising Model. Equilibrium and Non-Equilibrium Properties.- V Excitations in Ordered Magnets.- Theory of the Raman and Brillouin Scattering on the Excited Electronic States and Magnons in Europium Chalcogenides.- Effect of a Surface on Magnon-Magnon Interactions in Ferromagnets.- Correlation Theory of Magnetic Excitations.- A Rescaling Approach to Excitations in Magnetic Systems.- VI Novel Magnetic Models and Systems.- Monte Carlo Study of the 2-Dimensional Spin-½ XY Model.- Quenching of Spin Fluctuations in Highly Enhanced Magnetic Materials.- Quasiparticle Model for High Frequency Inelastic Neutron Scattering from Intermediate Valence Compounds.- Singlet Ground-State Dimer Systems Cs3Cr2Br9 and Cs3Cr2Cl9.- Helimagnetism in the Heisenberg Model: New Features and Old Mechanisms.- Magnetic Excitations in the Quasi-2d Planar Magnets BaM2((XO)4)2 (M=Co,Ni; X=P,As).- Spin Dynamics of Rare Earth Ions in Crystal Fields Probed by Muon Spin Rotation.- Ground-State Properties of s = 1 Easy-Plane Ferromagnetic Heisenberg Chains.- Bound State of Phonons and CEF-Excitations in CeAl2.- Local Magnetic Field Distributions in Ising Models.- List of Contributors.