Pressure dependence of Curie temperature and resistivity in complex Heusler alloys

TL;DR

This study uses first-principles calculations to explore how hydrostatic pressure affects the Curie temperature and resistivity in Ni2MnSn Heusler alloys doped with Cu and Pd, revealing pressure-induced variations and underlying exchange interactions.

Contribution

It provides a detailed theoretical analysis of pressure effects on magnetic and transport properties in doped Heusler alloys, including new insights into the crossover behavior of Curie temperature with pressure.

Findings

Curie temperature increases with pressure in (Ni1-x,Pdx)2MnSn alloys.

Crossover from increasing to decreasing Curie temperature occurs at about 70% Cu doping.

Resistivity contributions from spin disorder are quantified using the disordered local moment model.

Abstract

Using first-principles electronic structure calculations, we have studied the dependence of the Curie temperature on external hydrostatic pressure for random Ni2MnSn Heusler alloys doped with Cu and Pd atoms, over the entire range of dopant concentrations. The Curie temperatures are calculated by applying random-phase approximation to the Heisenberg Hamiltonian whose parameters are determined using the linear response and multiple scattering methods, based on density-functional theory. In (Ni1-x,Pdx)2MnSn alloys, the Curie temperature is found to increase with applied pressure over the whole concentration range. The crossover from the increase to the decrease of the Curie temperature with pressure takes place for Cu concentrations larger than about 70% in (Ni1-x,Cux)2MnSn Heusler alloys. The results for the reference Ni2MnSn Heusler alloy agree well with a previous theoretical study of E. Sasioglu, L. M. Sandratskii and P. Bruno Phys. Rev. B 71 214412 (2005) and also reasonably well with available experimental data. Results for the spin-disorder-induced part of the resistivity in (Ni1-x,Pdx)2MnSn Heusler alloys, calculated by using the disordered local moment model, are also presented. Finally, a qualitative understanding of the results, based on Anderson's superexchange interaction and Stearn's model of the indirect exchange interaction between localized and itinerant d electrons, is provided.