High T$_C$ ferromagnetic inverse Heusler alloys: A comparative study of Fe$_2$RhSi and Fe$_2$RhGe

TL;DR

This study compares Fe₂RhSi and Fe₂RhGe inverse Heusler alloys, revealing their structural, magnetic, and electronic properties, with Fe₂RhSi identified as a high-temperature, half-metallic ferromagnet suitable for spintronics.

Contribution

The paper combines experimental and first-principles calculations to identify Fe₂RhSi as a half-metallic ferromagnet with high ordering temperature, advancing understanding of inverse Heusler alloys.

Findings

Fe₂RhSi is a half-metallic ferromagnet.

Both alloys crystallize in inverse Heusler structure with disorder.

Fe₂RhSi has a high saturation magnetic moment of 5.00 μ_B.

Abstract

We report the results of experimental investigations on structural, magnetic, resistivity, caloric properties of Fe$_2$RhZ (Z=Si,Ge) along with \textit{ab-initio} band structure calculations using first principle simulations. Both these alloys are found to crystallize in inverse Heusler structure but with disorder in tetrahedral sites between Fe and Rh. Fe$_2$RhSi has saturation moment of 5.00 $\mu_B$ and while its counterpart has 5.19 $\mu_B$. Resistivity measurement reveals metallic nature in both of them. Theoretical simulations using generalized gradient approximation(GGA) predict inverse Heusler structure with ferromagnetic ordering as ground state for both the alloys. However it underestimates the experimentally observed moments. GGA+$U$ approach, with Hubbard $U$ values estimated from density functional perturbation theory helps to improve the comparison of the experimental results. Fe$_2$RhSi is found to be half metallic ferromagnet while Fe$_2$RhGe is not. Varying $U$ values on Fe and Rh sites does not change the net moment much in Fe$_2$RhSi, unlike in Fe$_2$RhGe. Relatively small exchange splitting of orbitals in Fe$_2$RhGe compared to that of Fe$_2$RhSi is the reason for not opening the band gap in the minority spin channel in the former. High ordering temperature and moment make Fe$_2$RhSi useful for spintronics applications.