Amorphous Heusler alloys: The effect of annealing on structure and magnetic and transport properties

Abstract

Alloys with the Heusler compositions Cu2MnIn, Cu2MnAl and Cu2MnSn have been prepared as amorphous films for the first time. The structural disorder results in as-deposited films which are not ferromagnetic and, in fact, exhibit spin-glass properties due to the distribution of MnMn distances and co-existence of positive and negative exchange interactions. Annealing of the In and Al alloys can restore single phase ordered Heusler structures which are ferromagnets with Curie temperatures typical of bulk alloys. The calculated Mn moments remain lower than the bulk values of 4 μB probably due to disorder at grain boundaries. Films annealed under non-optimum conditions crystallized into several non-magnetic structures as well as the magnetic L21 Heusler phase. Lattice constants of all phases were determined. The temperature dependence of resistivity through the amorphous-crystalline transformation was found to confirm the results of thermal annealing on structure and magnetization. © 1982.