Study of the effect of disorder on the local magnestism in Heusler alloys

Abstract

A local study of the influence of annealing temperature that can provoke structural defects and chemical disorder on the magnetism of Heusler alloys has been carried out by measuring hyperfine interactions in Pd2MnZ (Z=Ge, In, Sn, and Sb). Perturbed angular correlation method has been used to measure the hyperfine fields at 111Cd probe nuclei substituting the Mn and Z sites as a function of temperature. The fraction of 111In-nuclei-occupying Mn sites was found to increase with the annealing of sample at higher temperatures followed by quenching that can leave the alloy in a disordered state. As a consequence, it was possible to observe the effect of temperature in the ordering of the alloys. Moreover, electric quadrupole interaction measurements clearly indicated chemical disorder after quenching in Pd2MnSn and an improvement in the ordering of the Pd2MnGe structure at high temperatures.