Abstract

The usual Heisenberg Hamiltonian with bilinear exchange -2JS→1•S→2 has been extended to include a biquadratic term -2αJ(S→1•S→2)2, with an adjustable parameter α. A method equivalent to constant coupling was employed to calculate the effect of the biquadratic exchange term on the Curie temperature, magnetization, susceptibility, specific heat, and entropy for lattices with spin-1 atoms. As α goes from 0 to 1, the Curie temperature falls by a factor 2 to 3, while the asymptotic Curie temperature is reduced by the factor 2. The magnetization rises much more rapidly below TC, and the specific heat has a peak and discontinuity several times higher for α=1. The curvature of the inverse susceptibility increases with α, as does the entropy change taking place above TC. © 1971 The American Physical Society.

Department(s)

Physics

International Standard Serial Number (ISSN)

0163-1829

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2023 American Physical Society, All rights reserved.

Publication Date

01 Jan 1971

Included in

Physics Commons

 
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