Physical properties of half-Heusler YMnZ (Z = Si, Ge, Sn) compounds via ab-initio study

We have contemplated the basic structural stability, electronic, magnetic and thermoelectric properties of the newly predicted half-metallic (HM)YMnZ (Z = Si, Ge, Sn) alloys in half-Heusler (HH) phase with optimized lattice constants by ab-initio full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method using density functional theory (DFT). We have explored MgAgAs (C1_b-type) structure of these HH YMnZ materials in three different atomic arrangements (X-type1, X-type2, X-type3) and found X-type1 structure is energetically more favorable for YMnSi and YMnGe whereas YMnSn prefers the X-type2 structure. Moreover, non-magnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) states computed for YMnZ HH materials favor FM states. The presence of the energy gap in the majority spin bands and density of the states within the HH YMnZ are indications of potential HM ferromagnetism. For the lattice constant range of 6.2 Å to 7.4 Å, the total magnetic moment remains integral value of 4.0μ_B per formula unit and obeys the modified Slater-Pauling rule. The calculations reveal that YMnZ display HM ferromagnetism having the total magnetic moment of 4.00 μ_B which primarily arises from the spin-polarization of d-electrons of Mn atom and partial involvement of p-electrons of Z-atom. The half-metallicity of YMnZ materials might show that they are ideal for applications in spin polarizers and spin injectors of magnetic nano-devices due to their larger half-metallic gaps, which mean that they are steady at ambient conditions. The robustness associated with half-metallicity contrary to the lattice constant is additionally ascertained for desirable spintronics applications. Thermoelectric properties of the YMnZ materials are additionally computed over an extensive variety of temperature and it is discovered that YMnSi demonstrates higher figure of merit than YMnGe and MnSn.