Magnetic, Electronic, Mechanic, Anisotropic Elastic and Vibrational Properties of Antiferromagnetic Ru2TGa (T = Cr, Mn, and Co) Heusler Alloys

Abstract

A theoretical study of magnetic, electronic, mechanic, anisotropic elastic, and vibrational properties of $$ {\hbox{Ru}}_{2} $$ TGa (T = Cr, Mn, and Co) Heusler alloys has been extensively investigated by the first-principles method using the generalized gradient approximation. Structural parameters such as lattice constant ( $$ a_{0} $$ ), bulk modulus (B) and first pressure derivative of bulk modulus (B′) were obtained by using the Murnaghan equation. The calculated formation enthalpies ( $$ \Delta H_{f} $$ ) showed that these alloys are thermodynamically stable. The total spin magnetic moments per unit cell of $$ {\hbox{Ru}}_{2} $$ TGa (T = Cr, Mn, and Co) alloys were found to be 1.16 $$ \mu_{B} $$ , 2.16 $$ \mu_{B} $$ and 0.29 $$ \mu_{B} $$ , respectively. In addition to electronic band structures along the high symmetry directions, corresponding total and partial density of states were also plotted. It was found that the spin-up states have a metallic character for all alloys, but the spin-down states of the other alloys except for $$ {\hbox{Ru}}_{2} $$ CoGa have a pseudo-gap at the Fermi level. The bulk modulus (B), shear modulus ( $$ G $$ ), ratio of B/ $$ G $$ , Young’s modulus (E), Poisson’s ratios (ν), Vickers hardness ( $$ H_{V} $$ ), sound velocities ( $$ v_{l} $$ , $$ v_{t} $$ , and $$ v_{m} $$ ), Debye temperatures ( $$ \varTheta_{D} $$ ) and melting temperatures ( $$ T_{\rm{melt}} $$ ) were obtained from elastic constants ( $$ C_{ij} $$ ) in accordance with the Voigt–Reuss–Hill approximation. The calculated elastic constants showed that these alloys are mechanically stable and they have anisotropic character. The elastic anisotropy of the considered alloys was analyzed and pictured in great detail with 2D and 3D figures of directional dependence of Young’s modulus, linear compressibility, shear modulus, and Poisson’s ratio.These alloys are dynamically stable because there are no negative modes in their phonon dispersion curves.