Giant Coercivity and Spin-Valve Behavior of Mn ₂ IrGa: A Ferrimagnetic Spin Semimetal

Spin semimetals are a class of spintronic materials that exhibit a band gap in one spin channel and semimetallic features in the other, thus facilitating tunable spin transport. Here, we report Mn2IrGa as a candidate material for spin semimetals, along with giant coercivity and spin-valve characteristics, using a combined experimental and theoretical study. The alloy crystallizes in an inverse Heusler structure (without any martensitic transition) with a para- to ferrimagnetic transition at TC ∼ 243 K. It shows a giant coercive field of about 8.5 kOe (at 2 K). The negative temperature coefficient of resistivity (ρ), along with the low magnitude and weak temperature dependence of ρ, suggests the semimetallic character of the alloy. This is further supported by our specific heat measurements. Magnetoresistance (MR) confirms an irreversible nature (with magnitude ∼ 1%) along with a change of sign across the magnetic transition, indicating the potential of Mn2IrGa in magnetic switching applications. In addition, the asymmetric nature of MR in the positive and negative field cycles suggests spin-valve characteristics in this bulk alloy. Our ab initio calculations confirm the inverse Heusler structure with ferrimagnetic ordering to be the lowest energy state, with a saturation magnetization of 2 μB/f.u. <100> found to be the easy magnetic axis with considerable magnetocrystalline anisotropy energy. A large positive Berry flux at/around the Γ point gives rise to an appreciable anomalous Hall conductivity (about −180 S/cm).