1210.2188 (P. A. Igoshev et al.)

Competing magnetic fluctuations in gamma-iron due to peculiarities of
its electronic structure    [PDF]

P. A. Igoshev, A. V. Efremov, A. A. Katanin, A. I. Poteryaev, V. I. Anisimov

Applying the local density and dynamical mean field approximations to paramagnetic gamma-iron, we revisit a problem of theoretical description of its magnetic properties in a wide temperature range. We show that contrary to alpha-iron, the frequency dependence of the electronic self-energy has a quasiparticle form for both, t2g and eg states. The momentum dependence analysis of static magnetic susceptibility shows maximum near the wave vector q_X=(2 pi,0,0), in agreement with the experimentally observed antiferromagnetic state in gamma-iron precipitates. This state is however found to closely compete with the states, characterized by magnetic wave vectors along the directions q_X--(pi,pi,pi)--(3 pi/2,3 pi/2,0). From the analysis of the uniform magnetic susceptibility we find, that contrary to alpha-iron, the Curie-Weiss law is not fulfilled in a broad temperature range, although the inverse susceptibility is nearly linear in the moderate--temperature region (1200--1500 K). This non-linearity of the inverse uniform magnetic susceptibility in broader temperature range is due to the density of states peak located in the vicinity of the Fermi level. Based on the obtained momentum dependence of the susceptibility in the paramagnetic phase the exchange integrals are estimated. The obtained results allow us to ascertain the size of the correlation effects in gamma-iron as weak to moderate and give evidence of close relation of gamma-iron to the other weak itinerant antiferromagnets.

View original: http://arxiv.org/abs/1210.2188