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A Green‐function theory of an anisotropic ferromagnet
Author(s) -
Pandey R. B.,
Bhandari C. M.
Publication year - 1976
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.2220780243
Subject(s) - anisotropy , condensed matter physics , magnetization , decoupling (probability) , ferromagnetism , magnetic anisotropy , limiting , physics , function (biology) , series expansion , magnetic field , quantum mechanics , mechanical engineering , control engineering , evolutionary biology , engineering , biology
Green's function technique is used to investigate the magnetic properties of a wide range of anisotropic ferromagnets. A method of terminating the series of equations through the standard spin identity for spin‐1 systems is used to treat the Green functions without decoupling and to obtain a set of coupled equations. Magnetization 〈 S z 〉 and 〈( S z ) 2 〉 are studied as a function of different anisotropic parameters, i.e. single‐ion crystal‐field anisotropy parameters D 1 and D 2 , exchange‐anisotropy parameters η 1 and η 2 , and temperature. Analytic expressions are derived in some limiting cases. In the absence of crystal‐field anisotropy expressions for magnetization and critical temperature as functions of exchange anisotropies are obtained by series expansion methods. All these physical properties are discussed in different models and are in limiting cases in agreement with some earlier results.