2003/06/30 by Annamaria Kiss, Annamária Kiss, P. Fazekas · 3 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic and transport properties of perovskites and related materials #Rare-earth and actinide compounds #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.68.174425
published as Physical Review B 68, 174425 (2003) · 29 pages, 10 figures LaTeX In its contents, the present version agrees with the published one (see Journal Reference below). Essential additions to the text in Sec. III, otherwise some change of wording, and minor corrections
openalex publication_date 2003/11/21 · arxiv created 2004/04/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We study f-electron lattice models which are capable of supporting octupolar, as well as dipolar and quadrupolar, order. Analyzing the properties of the \ensuremathΓ8 ground-state quartet, we find that (111)-type combinations of the \ensuremathΓ5 octupoles T111^\ensuremathβ=Tx^\ensuremathβ+Ty^\ensuremathβ+Tz^\ensuremathβ are the best candidates for octupolar order parameters. Octupolar ordering induces \ensuremathΓ5-type quadrupoles as secondary order parameter. Octupolar order is to some extent assisted, but in its basic nature unchanged, by allowing for the presence of quadrupolar interactions. In the absence of an external magnetic field, equivalent results hold for antiferro-octupolar ordering on the fcc lattice. In this sense, the choice of our model is motivated by the recent suggestion of octupolar ordering in NpO2. The bulk of our paper is devoted to a study of the effect of an external magnetic field on ferro-octupolar ordering. We found that octupolar order survives up to a critical magnetic field if the field is lying in specific directions, while for general field directions, the underlying symmetry of the model is destroyed and therefore the phase transition suppressed even in weak fields. Field-induced multipoles and field-induced couplings between various order parameters are discussed on the basis of a group-theoretical analysis of the Helmholtz potential. We also studied the effect of octupolar ordering on the nonlinear magnetic susceptibility which satisfies Ehrenfest-type relations at continuous octupolar transitions.