Magnetic hyperfine interactions and compositional short range order in the Heusler alloys Cu 2MnIn 1- xSn x

Abstract

A comprehensive study of the magnetic hyperfine interactions and the processes of crystallographic ordering in the Heusler alloy system Cu 2MnIn 1- x Sn x has been made. We report the results of Mössbauer effect experiments, X-ray diffraction studies, electrical transport, and Curie temperature measurements. By a rapid quenching, low temperature annealing technique we have been able to extend the ordered L2 1 structure to high Sn concentration. Observations of inequivalent Sn sites and nonunique 119Sn hyperfine field values in these alloys are shown to be due to difficulties in ordering the L2 1 structure and a basic instability of this phase for high Sn concentrations. The compositional variation of 119Sn hyperfine fields in the ordered L2 1 phase of the Cu 2MnIn 1- x Sn x system reveals a systematic increase with Sn composition. Calculations of these fields based on a homogeneously spin polarized electron gas model reproduce the observed field systematics quite well. The implications of these results on the nature of magnetic interactions in Heusler alloys are discussed.