Stable and metastable states in iron–manganese pnictides of the system Fea−xMnxAs

Abstract

The first-order magnetic phase transitions of the order–order type induced by magnetic field in the layered antiferromagnetic alloys of the system Fea−xMnxAs are analyzed in the model of itinerant magnetism with allowance for the possible coexistence of ferromagnetic and antiferromagnetic deformations of the electronic band structure. In the abstraction to a model description of Fea−xMnxAs a single-band energy spectrum is used in which the filling of the band and the electronic density of states are chosen on the basis of first-principles calculations of the nonmagnetic and ferrimagnetic states. It follows from the results of the this analysis that the order–order transitions might be caused by a slight transformation of the electronic density of states and a change of the degree of filling of the magnetically active band. Such changes may be a consequence of thermal fluctuations of the spin density and pressure. The role of pressure and of the magnetostrictive contribution to the order–order transitions is discussed.