Premium
On the Diagram Technique for Green Functions of the Heisenberg Ferromagnet
Author(s) -
Kühnel A.
Publication year - 1986
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.2221370110
Subject(s) - commutation , diagram , ferromagnetism , spin (aerodynamics) , physics , magnetization , function (biology) , energy (signal processing) , phase diagram , theoretical physics , condensed matter physics , mathematics , quantum mechanics , thermodynamics , statistics , phase (matter) , voltage , evolutionary biology , biology , magnetic field
The Green function approach to the Heisenberg ferromagnet is confronted with the difficulties connected with the commutation rules of spin operators. Recently, Baryakhtar, Krivoruchko, and Yablonskii (BKY) proposed a new diagram technique for Green functions containing spin operators based on the corresponding technique by Izyumov and Kassan‐Ogly. The new approach is compared with that proposed earlier by Haberlandt and Kühnel. Calculating some crucial terms it is shown why the diagrams of BKY do not represent the corresponding analytical terms properly if kinematic interaction due to the peculiar commutation relations is involved. The results for the low temperature spin wave energy and magnetization are discussed.