High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>T</mml:mi><mml:mi>C</mml:mi></mml:msub></mml:math>ferromagnetic inverse Heusler alloys: A comparative study of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Fe</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>RhSi</mml:mi></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Fe</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>RhGe</mml:mi></mml:math>
Venkateswara Yenugonda, S. Shanmukharao Samatham, Akhilesh Kumar Patel, P. D. Babu, Manoj Raama Varma, К. Г. Суреш, Aftab Alam
Abstract
We report the results of experimental investigations on structural, magnetic, resistivity, and caloric properties of ${\mathrm{Fe}}_{2}\mathrm{RhZ}$ (Z = Si,Ge) along with ab initio band structure calculations using first-principle simulations. Both alloys are found to crystallize in inverse Heusler structure but with disorder in tetrahedral sites between Fe and Rh. ${\mathrm{Fe}}_{2}\mathrm{RhSi}$ has a saturation moment of $5.00\phantom{\rule{4pt}{0ex}}{\ensuremath{\mu}}_{B}$ and while its counterpart has $5.19\phantom{\rule{4pt}{0ex}}{\ensuremath{\mu}}_{B}$. Resistivity measurement reveals a metallic nature in both of them. Theoretical simulations using generalized gradient approximation (GGA) predict an inverse Heusler structure with ferromagnetic ordering as a ground state for both alloys. However, it underestimates the experimentally observed moments. $\mathrm{GGA}+U$ approach, with Hubbard $U$ values estimated from density functional perturbation theory, helps to improve the comparison of the experimental results. ${\mathrm{Fe}}_{2}\mathrm{RhSi}$ is found to be a half-metallic ferromagnet while ${\mathrm{Fe}}_{2}\mathrm{RhGe}$ is not. Varying $U$ values on Fe and Rh sites does not change the net moment much in ${\mathrm{Fe}}_{2}\mathrm{RhSi}$, unlike in ${\mathrm{Fe}}_{2}\mathrm{RhGe}$. Relatively small exchange splitting of orbitals in ${\mathrm{Fe}}_{2}\mathrm{RhGe}$ compared to that of ${\mathrm{Fe}}_{2}\mathrm{RhSi}$ is the reason for not opening the band gap in the minority spin channel in the former. High ordering temperature and moment make ${\mathrm{Fe}}_{2}\mathrm{RhSi}$ useful for spintronics applications.