Peculiarities of the spontaneous and magnetic-field-induced magnetically ordered phases in alloys of the Mn2−xFexAs0.5P0.5 system

Abstract

The phase diagram of the system Mn2−xFexAs0.5P0.5 is investigated experimentally and theoretically. The existence of an antiferromagnetic phase for alloys with x<0.7 is revealed. It is shown that in the region 0.5<x<0.8, ferromagnetism and antiferromagnetism can coexist in the low-temperature phase, which possesses spontaneous magnetization. This phase can be described as a canted ferromagnetic structure. The electronic structure of the alloy Mn1.5Fe0.5As0.5P0.5 is calculated in the ferromagnetic and nonmagnetic states. A comparison of the calculated and experimental values of the magnetic moment per formula unit shows that a pure ferromagnetic state is realized only in alloys with x>0.8, for which those values are in good agreement. A model is constructed that can describe correctly the main features of the spontaneous and magnetic-field-induced magnetically ordered states observed in the given system. The parameters of the model are the degree of filling of the d band, the nonmagnetic density of electronic states, and the interatomic exchange integral. Their values are estimated from the data of electronic structure calculations from first principles. The model has made it possible to predict and experimentally observe the existence of a triple point on the state diagram of these alloys.