Structural, elastic, electronic, and magnetic properties of Si-doped Co2MnGe full-Heusler type compounds

Abstract

The structural, electronic, magnetic and elastic properties of Co2MnGe1-xSix (x = 0, 0.25, 0.50, 0.75, and 1) compounds are investigated by first-principles calculations within the generalized gradient approximation (GGA). The calculated structural parameters of these compounds show a slightly decreasing lattice constants and similarly decreasing lattice volumes and enthalpies of formation on increasing Si substitution x. The band structure calculations estimate that these compounds at their optimized lattice constants are half-metallic ferromagnets. The calculated total magnetic moment values are all integers, which is typical for half-metallic materials with a half-metallic bandgap (EHM) in the minority states. Besides, the total magnetic moments of these compounds are fully compatible with the Slater-Pauling rule showing the half-metallicity and large spin polarization desired for spintronics applications. The partial substitution of the Ge atom by the Si does not affect the atomic magnetic moment and total magnetic moment. The obtained values of structural parameters, total and atomic magnetic moments for x = 0 and 1 stoichiometric compounds are in good agreement with experimental and theoretical results. The elastic constants are studied for all compositions of x in order to verify the mechanical stability of these compounds. Born’s stability criterion implemented on elastic constants of Co2MnGe1-xSix (x = 0, 0.25, 0.50, 0.75, and 1) compounds confirm that these materials are mechanically stable. Other elastic parameters like bulk modulus (B), shear modulus (G), ratio of B/G, Young’s modulus (E), Poisson’s ratio (ν), and Shear anisotropic factor (A), which are the significant elastic moduli for technological applications have been thoroughly investigated. Consequently, these compounds, especially Co2MnGe1-xSix (x = 0.25, 0.50, 0.75) mixed systems, are promising candidates for practical applications in the field of spin electronics.