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"Extended Heisenberg Hamiltonian for LaMn2X2 (X=Si,Ge) using an ab initio parametrization"
V. Massidda, S. Di Napoli and A.M. Llois
Proc. of the Workshop "At the Frontiers of Condensed Matter II - Magnetism, Magnetic Materials, and their Applications", Buenos Aires, Argentina, June 22-26, 2004. Ed. C. Saragovi, J. Guevara, R. Weht, A.M. Llois and M.T. Causa
Physica B Condens. Matter. 354(1-4) (2004) 232-236
The two compounds LaMn2Ge2 and LaMn2 Si2 exhibit different noncollinear and collinear magnetic structures and temperature-driven transitions between them. A phenomenological study of the behaviour of each of them requires a Hamiltonian containing the interactions between the localized moments. We assume a model Hamiltonian with bilinear, biquadratic and anisotropic interactions for which the interaction constants are taken from ab initio calculations and evaluate the free energies of the above-mentioned configurations within a mean field approximation (MFA). The experimentally observed phase sequences are obtained for both compounds.
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