Longitudinal and transverse static spin fluctuations in layered ferromagnets and antiferromagnets

A. Katanin

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3 Citations (Scopus)


We analyze the momentum dependence of static susceptibilities of layered local-moment systems below Curie (Neel) temperature within the 1/S expansion, the renormalization-group (RG) approach, and the first order of the 1/N expansion. We argue that already at sufficiently low temperatures the previously known results of the spin-wave theory and RG approach for the transverse spin susceptibility acquire strong corrections, which appear due to the interaction of the incoming magnon having momentum q with virtual magnons having momenta k<q. Such corrections cannot be treated in the standard RG approach but can be described by both 1/S and 1/N expansions. The results of these expansions can be successfully extrapolated to T=TM, yielding the correct weight of static spin fluctuations, determined by the O(3) symmetry. For the longitudinal susceptibility, the summation of leading terms of the 1/S expansion within the parquet approach allows us to fulfill the sum rule for the weights of transverse and longitudinal fluctuations in a broad temperature region below TM outside the critical regime. We also discuss the effect of longitudinal spin fluctuations on the (sublattice) magnetization of layered systems.

Original languageEnglish
Article number224416
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number22
Publication statusPublished - 21 Dec 2012
Externally publishedYes


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