Magnetism and exchange coupling in iron pnictides

TitleMagnetism and exchange coupling in iron pnictides
Publication TypeJournal Article
Year of Publication2010
AuthorsPulikkotil JJ, Ke L, van Schilfgaarde M, Kotani T, Antropov VP
Journal TitleSuperconductor Science & Technology
Volume23
Pages054012
Date Published05/01
ISBN Number0953-2048
Accession NumberISI:000277029800017
Keywordsspin dynamics
Abstract

Using linear-response density-functional theory, we obtain the magnetic interactions in several iron pnictides. The ground state has been found to be non-collinear in FeSe, with a large continuum of nearly degenerate states lying very close to the magnetic 'striped' structure. The presence of non-collinearity also seems to be a generic feature of iron pnictides when the Fe moment is small. At small RFe-Se the system is itinerant: strong frustration gives rise to an excess of spin entropy, long ranged interactions create incommensurate orderings and strong biquadratic coupling violates the applicability of the Heisenberg model. There is a smooth transition to more localized behavior as RFe-Se increases: stable magnetic orbital order develops which favors long range AFM stripe ordering with strongly anisotropic in-plane exchange couplings. The stabilization of the stripe magnetic order is accompanied by the inversion of the exchange coupling.

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