The Heisenberg ferromagnet with higher-order exchange
- 1 February 1979
- journal article
- Published by IOP Publishing in Journal of Physics C: Solid State Physics
- Vol. 12 (3) , 575-583
- https://doi.org/10.1088/0022-3719/12/3/023
Abstract
The authors investigate the properties of ferromagnetic spin systems with higher-order exchange interactions, in particular with four-spin terms of the form (Si.Sj)(Sk.Sl) and (Si.Sj)(Sj.Sk). Using the Green function equation of motion method, and simple decoupling approximations, they obtain renormalised spin-wave energies, magnetisation curves, and critical temperatures for various strengths of the four-spin interactions. For sufficiently large values of these interactions the transition becomes first order. For comparison they also give the results of spin-wave and mean-field theories.Keywords
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