Strain-driven half-metallicity in a ferri-magnetic Mott-insulator Lu2NiIrO6: a first-principles perspective

Abstract

Half-metallic ferromagnetic/ferrimagnetic (FiM) materials are a matter of enormous interest due to their potential technological applications in solid-state electronic devices. In this way, strain plays an important role to tune or control the physical properties of the systems; therefore, the influence of both biaxial ([110]) and hydrostatic ([111]) strain on the electronic and magnetic properties of recently synthesized double perovskite oxide Lu₂NiIrO₆ is investigated using density-functional theory calculations. The unstrained system exhibits a FiM Mott-insulating (i.e., having an energy gap of 0.20 eV) ground state due to strong antiferromagnetic superexchange coupling between high-energy half-filled Ni²⁺–e²_g↑ and low-energy partially filled Ir⁴⁺ t³_2g↑t²_2g↓ orbitals. Interestingly, a half-metallic FiM state is predicted under biaxial and hydrostatic compressive strains of −8% and −6%, respectively. The admixture of Ir 5d orbitals in the spin-majority channel is mainly responsible for the conductivity with small contributions from Ni 3d orbitals. In contrast, all the tensile strain systems show almost the same electronic behavior (Mott-insulating FiM states) as found in the case of the unstrained system. The magnetic moments of the Ni (Ir) ion slightly decrease and increase as a function of compressive and tensile strains due to shortening and lengthening of the Ni–O(Ir–O) bond lengths, respectively. Moreover, our calculations show that compressive strain enhances the structural distortions, which could help to increase the Curie temperature of the system.