Properties Of half-Heusler Compounds Research Articles

Topological properties of half Heusler compounds: Tuned by the spin-orbit coupling and p-d hybridization

The topological properties of Half Heusler compounds XYZ (X=Na, K; Y=Cu, Ag, Au; Z=S, Se, Te) are studied by the density functional theory (DFT) and tight-binding model Hamiltonian. The Y-s, Y-d and Z-p states form the bands around the Fermi level and determine their topological properties. When the energy of Y-s state is much larger than the other states, the compounds are normal insulators, just like NaCuS and NaCuS. On the contrary, when the Y-s state energy is only a little higher than the other states, the compounds are topological insulators (TI) or Dirac semi-metal (DSM) depended on the effective spin orbital coupling (SOC), which can be tuned by the relation between positive SOC Z-p and Y-d states. The compounds with negative effective SOC are TI such as NaAgS, NaAuS, while the compounds possessing positive SOC are DSM, just like NaAgTe and NaAuTe. Our simple tight-binding model can be used to design topological materials before the time consuming DFT calculations.

Topological Properties of Half Heusler Compounds: Tuned by the Spin-Orbit Coupling and P-D Hybridization

Topological Properties of Half Heusler Compounds: Tuned by the Spin-Orbit Coupling and P-D Hybridization

First principles calculation of Manganese based half Heusler compounds

The Half-Heusler compounds exhibit a diverse range of tuneable properties including half-metallic ferromagnetism topological insulator, solar cells and thermoelectric converters. We have studied four half-Heusler compounds MnFeIn, MnFeGa, MnNiAs and MnNiSb. The nature and properties of half-heusler compounds can be studied on the bases of their valance electron count. In this paper, Fe based compounds have 18 valence electrons; whereas 22 valence electrons in Ni based. The Density Functional Theory (DFT) has been performed with WIEN2k code. Ni based compounds with Mn located at octahedral sites are half-metals as revealed from the Density of States (DoS) and band structure calculations. In all of them, spin-up channels are conducting; whereas in MnNiAs and MnNiSb spin-down channels have the small band gaps. MnNiAs and MnNiSb exhibit half-metallic property with integer magnetic moments of 4 μB per formula unit and half-metallic gaps of 0.15 and 0.17 eV at their equilibrium volume respectively.