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Perturbation Theory for a Spin System
Author(s) -
Trimper S.
Publication year - 1973
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220550129
Subject(s) - ferromagnetism , commutation , magnetization , perturbation theory (quantum mechanics) , perturbation (astronomy) , physics , spin (aerodynamics) , condensed matter physics , quantum mechanics , mathematical physics , magnetic field , thermodynamics , voltage
The spin 1/2 Heisenberg ferromagnet is treated by perturbation theory. To avoid the difficulties connected with the unusual commutation relations of spin operators the Dyson‐Maleev transformation is applied. The corresponding Bose system is described by the Bose‐Green function. To calculate the thermodynamic behaviour of the spin system a relation has been found between spin and Bose‐Green function. The low temperature expansion of the magnetization is calculated. No agreement is found using Dyson's standard result.