Magnetic Phase Transitions in the Fe₂As–Mn₂As System

Abstract

Magnetic and crystallographic measurements on Fe_2.1−xMn_xAs with 0≤x≤2.1 are made in the temperature range between 77 and 600 K. The compounds with 0≤x<1.29 and 1.52<x≤2.1 have the antiferromagnetic spin structures of the Fe₂As and Mn₂As types, respectively. The compounds with 1.29≤x≤1.52 show a first order phase transition between the ferrimagnetic state of the Mn₂Sb type and the antiferromagnetic state of the Fe₂As type. A magnetic phase diagram of Fe_2−xMn_xAs system is proposed and discussed qualitatively on the basis of the molecular field theory.