Magnetism of mixed quaternary Heusler alloys: (Ni,T)$_{2}$MnSn (T=Cu,Pd) as a case study

TL;DR

This study uses ab initio calculations to explore how doping Ni2MnSn Heusler alloys with Cu or Pd affects their magnetic, electronic, and transport properties, revealing complex behaviors of Curie temperatures and resistivity.

Contribution

It provides a comprehensive theoretical analysis of doped Ni2MnSn alloys, including magnetic moments, Curie temperatures, exchange interactions, and resistivity, with good agreement to experimental data.

Findings

Curie temperatures show nonlinear dependence on Cu doping.

Electronic structure near Fermi energy is weakly perturbed by dopants.

Resistivity behavior follows Nordheim rule and spin-disorder effects.

Abstract

The electronic properties, exchange interactions, finite-temperature magnetism, and transport properties of random quaternary Heusler Ni$_{2}$MnSn alloys doped with Cu- and Pd-atoms are studied theoretically by means of {\it ab initio} calculations over the entire range of dopant concentrations. While the magnetic moments are only weakly dependent on the alloy composition, the Curie temperatures exhibit strongly non-linear behavior with respect to Cu-doping in contrast with an almost linear concentration dependence in the case of Pd-doping. The present parameter-free theory agrees qualitatively and also reasonably well quantitatively with the available experimental results. An analysis of exchange interactions is provided for a deeper understanding of the problem. The dopant atoms perturb electronic structure close to the Fermi energy only weakly and the residual resistivity thus obeys a simple Nordheim rule. The dominating contribution to the temperature-dependent resistivity is due to thermodynamical fluctuations originating from the spin-disorder, which, according to our calculations, can be described successfully via the disordered local moments model. Results based on this model agree fairly well with the measured values of spin-disorder induced resistivity.