Structural, magnetic, electronic and mechanical properties of full-Heusler alloys Co2YAl (Y = Fe, Ti): First principles calculations with different exchange-correlation potentials

Abstract

The structural, magnetic, electronic, elastic and mechanical properties of full-Heusler compounds Co2YAl (Y=Fe, Ti), in L21 type structure are determined using the density functional theory based full potential linearized augmented plane waves (FP-LAPW) method. We have used four approaches to evaluate the structural stability for the two compounds, Co2FeAl and Co2TiAl, the Local Spin Density approximation (LSDA), the LSDA+USIC, the Spin-Perdew-Burke-Ernzerhof generalized gradient approximation GGA and PBE-GGA+USIC. The results show that the equilibrium lattice constants using the general gradient approximation method are in good agreement with experimental values. The electronic and magnetic properties of 3d transition metal based full Heusler compounds Co2YAl (Y=Fe, Ti) within the framework of Perdew-Burke-Ernzerhof generalized gradient approximation GGA, GGA+USIC besides new modified Becke and Johnson GGA (mBJ-GGA) have been calculated by exchange-correlation potentials. The calculated density of states (DOS) and band structure for Co2YAl show the existence of energy band gap in their minority-spin channel and half-metallic character, while their total magnetic moment following the Slater–Pauling rule Mt=Zt−24. The mechanical properties of bulk modulus, shear modulus, Young’s modulus E, anisotropic ratio, Poisson’s ratio ν and B/G ratio are also investigated to explore the ductile and brittle nature of these compounds. To collect more information on the mechanical stability, we have calculated Lame’s coefficients, Cauchy pressure, Kleinman parameter, sound velocities and Debye temperature θD Our calculated values are in agreement with experimental and theoretical data.