Effect of antiphase boundaries on the magnetic properties of Cu-Mn-Al Heusler alloys

Abstract

The magnetic properties of Heusler alloys of approximate composition Cu₂MnAl have been studied by Lorentz microscopy. as a function of composition, heat treatment and plastic deformation. Magnetic domain walls have been observed to be pinned at antiphase boundaries. The strength of pinning varies with composition and heat treatment, being strongest in alloys in which some of the aluminum has been replaced by copper, and in specimens which have been quenched from above the ordering temperature The pinning is thought to be due to antiferromagnetic coupling between the magnetic moments of manganese atoms on opposite sides of antiphase boundaries. Magnetic domain walls are also pinned at antiphase boundaries produced by the splitting of superlattice dislocations during plastic deformation. The results obtained by Lorentz microscopy provide an explanation for the variations of bulk magnetic properties with composition and heat treatment.