Phase transitions in the MnAs1-xSbx alloy system

Abstract

Single crystals of a continuous series of MnAs1-xSbx solid solutions are obtained and their crystal structure and magnetic properties are investigated in the temperature range from 150 to 600 K. It is shown that the crystal structure of MnAs, MnSb, and alloys with a small content of Sb and As, respectively, is characterized by uniaxial diplacements of atoms in the ferromagnetic state. At the temperature of the first order phase transition Tu the displacements in [001], [011], [011] directions become random. A layered magnetic structure with the ordered arrangement of moments in (100) and arbitrary multiples of 60° in the neighbouring layers is proposed. The destruction of the atter to the paramagnetic state occurs with a second order phase transition (at Tc). For single crystals of composition (0.3 ≦ x ≦ 0.8) the static displacements of Mn atoms are disordered, possibly by the structure defects; here the temperature dependence of the magnetization is described by the Brillouin function. From the data obtained a diagram of transformations (phase diagram) for MnAs1-xSbx single crystals is plotted.