Sobre a teoria das ondas de spin / On the theory of Spin waves

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

27/11/1984

RESUMO

The mathematical formalismo f the spin wave theory is analysed. The thermodynamical equivalence between the Dyson-Malleev and Holstein-Primakoff transformations is proved. The problems involving the kinematical interaction are also discussed in detail. A new splitting of the Heisenberg Hamiltonian, perfomed in configuration space, is used to study the spin wave dynamical interaction at low temperature and for large values of the spin quantum number S. Assuming the the kinematical restriction may be lifted, a low temperature espansion of the free energy is developed with results in agreement with Dysons. The relevance of the Mattis diagonal approximation for the dynamical interaction is demonstrated. Using the method of reflection positivity, upper and lower bounds to the contribuition of the dynamical interaction to the free energy are provided. In a certain approximation, these bounds mean that the dynamical interaction may be dropped IF the inverse temperature (=1/KT) and the spin quantum number S are large enough but depends on S in the estimates, a novel feature wich does not occur in the classical limit but is characteristic of the spin-wave limit.

ASSUNTO(S)

dyson holstein-primakoff transformation interação cinemática interação dinâmica interaction dynamics kinematics interaction ondas de spin spin waves transformação de dyson transformação de holstein-primakoff transformation

ACESSO AO ARTIGO

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