Lanthanum based quaternary Heusler alloys LaCoCrX (X = Al, Ga): Hunt for half-metallicity and high thermoelectric efficiency

Abstract

Ab-initio framework investigation of physical, structural stability, electro-magnetic, thermodynamic and transport behavior of quaternary La-based Heusler alloys carried out using spin-polarized calculations. The structural characterization in nonmagnetic, ferromagnetic and anti-ferromagnetic states reveal the ordered ferromagnetic LiMgPdSn-type structure as stable phase. The band structure profile show perfect half-metallic character with integral 3.00 µB magnetic moment according to the Slater-Pauling rule. From the temperature variation of Seebeck coefficients, LaCoCrAl (LaCoCrGa) show a descent value of −44 (−38) µV K−1 at 300 K, respectively, conveying the electrons favor the heat carrier mechanism with overall n-type behavior. Insight into variation of lattice thermal conductivity show an exponential decreasing trend for both the compounds intriguing their experimental exploration. The high-pressure study of the variation of specific heat follow the Dulong-Petit law, with low ranges of anharmonicity presence in both the compounds. Keywords: Half-metallic alloys, f-Electron system, Spin polarization, Seebeck coefficient