Structural, thermal, elastic, and magnetoelectronic properties of FeNiMnZ (Z = Al, Si) quaternary Heuslers under hydrostatic pressure

In this work, we have studied the structural, thermal, elastic and magnetoelectronic properties of FeNiMnZ (Z = Al, Si) Heuslers under pressure using the pseudo-potential plane wave method. The structural optimization was performed by considering three atomic arrangements in magnetic and non-magnetic states. It was found that FeNiMnZ Heuslers are chemically stable and crystallize in the ferromagnetic YI-type structure. At zero temperature (0 K) and zero pressure (0 GPa), the obtained lattice constant (a) and bulk modulus (B) are in good accordance with the literature. The determined elastic constants (Cij), Pugh’s ratio (B/G), and universal elastic anisotropy index (AU) under pressure reveal that FeNiMnZ Heuslers are mechanically stable up to 76 GPa, behave in a ductile manner, and exhibit a notable elastic anisotropy, respectively. The band structure analysis shows that FeNiMnAl Heusler compound changes from perfect half-metallic to a metallic nature at 50.2 GPa, while FeNiMnSi Heusler compound keeps its metallicity throughout the considered pressure range. The spin polarization and total magnetic moment of FeNiMnAl (FeNiMnSi) material decrease under pressure varying from 50.2 to 88 GPa (from 0 to 80 GPa). Below 50.2 GPa, FeNiMnAl material exhibits 100% spin polarization and a total magnetic moment of 4μB, which makes it hopeful in spintronic applications.