Concentration Fluctuations in FexMn1 – xSi Chiral Ferromagnets in an External Magnetic Field

Abstract

Magnetic h–T diagrams of FexMn1 – xSi chiral helicoidal ferromagnets with the Dzyaloshinskii–Moriya interaction are studied within the theory of spin fluctuations. A specific analysis of the magnetic equations of state is based on a model of the electronic structure resulting from the LDA + U + SO DOS calculations in the virtual-crystal approximation. It is shown that, in the region of concentrations x 0.12 and the region of the helicoidal ferromagnetic order is preserved up to concentrations xc = 0.20. In the interval 0.10 < x < 0.20, the fluctuation-induced transition to the paramagnetic state is accompanied by the disappearance of local magnetization and the formation of a paramagnetic state with dynamic spin correlations.