Phase transition in the magnetocrystalline anisotropy of tetragonal Heusler alloys: Rh$_2T$Sb, $T=$ Fe, Co

TL;DR

This study uses first principles calculations to explore how the magnetocrystalline anisotropy in tetragonal Rh$_2T$Sb Heusler alloys changes with Fe and Co composition, revealing a transition from easy-axis to easy-plane anisotropy around 40 ext% Fe.

Contribution

It provides new insights into the composition-dependent magnetic anisotropy transition in Rh$_2T$Sb Heusler alloys based on first principles calculations.

Findings

Magnetic moments increase with Fe content from 2 to 3.4 μ_B.

Curie temperature decreases from 500 to 464 K with Fe addition.

A transition from easy-axis to easy-plane anisotropy occurs at approximately 40 ext% Fe.

Abstract

This work reports on first principles calculations of the electronic and magnetic structure of tetragonal Heusler compounds with the composition Rh$_2$Fe$_{x}$Co$_{1-x}$Sb ($0\leq x\leq1$). It is found that the magnetic moments increase from 2 to 3.4~$\mu_B$ and the Curie temperature decreases from 500 to 464~K with increasing Fe content $x$. The $3d$ transition metals make the main contribution to the magnetic moments, whereas Rh contributes only approximately 0.2~$\mu_B$ per atom, independent of the composition. The paper focuses on the magnetocrystalline anisotropy of the borderline compounds Rh$_2$FeSb, Rh$_2$Fe$_{0.5}$Co$_{0.5}$Sb, and Rh$_2$CoSb. A transition from easy-axis to easy-plane anisotropy is observed when the composition changes from Rh$_2$CoSb to Rh$_2$FeSb. The transition occurs at an iron concentration of approximately 40\%.