One-Dimensional Easy-Plane Magnets: Classical Sine-Gordon Theory or a Quantum Model

摘要

A classical mechanics description of one-dimensional easy-plane ferro- and antiferromagnets predicts the existence of sine-Gordon kink excitations in these systems, for the case of a small applied field within the (''strong'') easy plane. Here we consider: (1) the deviations from the sine-Gordon model, due to stronger fields or weaker anisotropy, which result in modified kink properties, including negative effective masses and kink-antikink annihilation and reflection during collisions, and, (2) equilibrium thermodynamics, especially specific heat, for quantum spin S = 1/2, and S = 1 models, comparing with the predictions of classical sine-Gordon theory and with available experimental results. The applicability of a sine-Gordon model versus a quantum model or the full classical magnetic Hamiltonian is discussed, for materials such as CsNiF sub 3 , CHAB ((C sub 6 H sub 11 NH sub 3 )CuBr sub 3 ) and TMMC ((CD sub 3 ) sub 4 NMnCl sub 3 ). 27 refs., 7 fgis. (ERA citation 12:012867)