1201.1148 (A. Katanin)

Longitudinal and transverse static spin fluctuations in layered ferro-
and antiferromagnets    [PDF]

A. Katanin

We analyse the momentum dependence of static non-uniform susceptibilities of layered local-moment systems below Curie (Neel) temperature. While the spin-wave approach is applicable only at low temperatures, we extend its results for static spin susceptibilities to broader temperature range by considering the spin-wave interaction within the perturbation theory and first order of 1/N expansion. The latter approach treats the contribution of longitudinal, as well as critical fluctuations to transverse susceptibility. The obtained results for the transverse spin susceptibility are found to be different from those of the renormalization-group (RG) approach, but, contrary to the RG\ approach, fulfill the sumrule for the weight of the transverse and longitudinal fluctuations outside the critical regime (where the longitudinal susceptibility is described by the ladder (parquet) approach) and at $T=T_{N}$ (where the O(3) symmetry arguments can be applied). We also discuss the effect of longitudinal spin fluctuations on the (sublattice) magnetization of layered systems.

View original: http://arxiv.org/abs/1201.1148