Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/80000
Type: Artigo de periódico
Title: HIGH-TEMPERATURE DIPOLAR LOCAL FIELD CORRELATIONS IN 2-DIMENSIONAL EXCHANGE-COUPLED SYSTEMS
Author: GENNARO, AM
LEVSTEIN, PR
Abstract: High-temperature local field correlations are needed to calculate the angular variation of the electron spin resonance (ESR) linewidth of exchange-coupled systems in the paramagnetic phase. In low-dimensional magnetic systems, these time correlations are usually calculated by appealing to arbitrary intermediate functions to interpolate between short- and long-time regimes. In this work, we calculate the correlation function of the dipolar field in a two-dimensional (2D) square lattice of spins 1/2, for several orientations of an external magnetic field. Arbitrary interpolation functions are avoided by assuming that the normal modes of the spin correlations behave diffusively as soon as quantum coherence is broken. The effects of interlayer exchange in an actual system are considered by introducing a cut-off in the 2D diffusion. The angular variation of the resulting ESR linewidth is analysed as a function of the 'quantum coherence time' tau-0 and the cut-off time tau-c. Comparison with experimental data in layered Cu-amino acid crystals allows us to estimate tau-0 less-than-or-equal-to 0.5h/J and tau-c congruent-to 200h/J, where J is the in-layer exchange.
Country: Inglaterra
Editor: Iop Publishing Ltd
Rights: fechado
Identifier DOI: 10.1088/0953-8984/3/4/009
Date Issue: 1991
Appears in Collections:Unicamp - Artigos e Outros Documentos

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