Magnetic structure in ordered FeCr

Abstract

The magnetic phases of FeCr in the ${\mathrm{CsCl}\mathrm{}(\mathrm{B}}_{2})$ structure have been studied by three methods: (1) the full-potential linearized-augmented-plane-wave (FLAPW) method with a local-spin-density approximation without relativistic corrections, (2) the FLAPW method with the Perdew-Burke-Ernzerhof exchange-correlation potential in a generalized-gradient approximation, and (3) the augmented-spherical-wave method with the fixed-spin-moment procedure without nonlocal and relativistic corrections. Unusual antiferromagnetic (AF) and ferromagnetic (FM) phases are found from all these calculations; e.g., in the AF phase, both the Fe and the Cr sublattices are separately AF at large enough lattice constant; in the FM phase, the Fe and Cr sublattices have opposite FM moments at large lattice constants. With method (3), a second FM phase is found in which the moments of the two Fe atoms have different magnitudes and even opposite signs at large lattice constants. Methods (1) and (3) agree well in energy and moment values as functions of volume, but method (2) increases the equilibrium lattice constant by 1.9% and the average FM magnetic moment by 7.8% at equilibrium compared to method (1).