Insulator-to-metal transition, magnetic anisotropy, and improved T C in a ferrimagnetic La 2 CoIrO 6 : strain influence.

The elegant interactions between Coulomb repulsion and spin-orbit coupling in Ir-based double perovskite oxides (DPO) normally induce peculiar magnetic behavior. Herein, we investigate the effect of the development of biaxial [110] strain on the formation energetics, and electronic and magnetic properties of the La 2 CoIrO 6 DPO employing density functional theory calculations. Our results reveal that the unstrained motif is a Mott-insulator achieving an energy band gap of 0.35 eV with a ferrimagnetic (FiM) ground state, which essentially arises due to anti-ferromagnetic (AFM) coupling between the half-occupied Co t 2g and partially occupied Ir t 2g /empty e g orbitals via oxygen 2p states. Along with this, it is found that [001] ( c -axis) is the easy magnetic axis, which results in 12.5 meV total energy per u.c., obtaining a large anisotropy constant of 0.8 × 10 8 erg cm -3 . The computed partial spin-magnetic moments on the Co/Ir ion are 2.64/-0.46 μ B , where the negative sign on the Ir ion moment confirms the AFM interactions between them. Additionally, the t 2g /e g and t 2g orbital characteristics of Co 2+ and Ir 4+ ions are visible in the spin-magnetization density isosurfaces plot, respectively. Likewise, the estimated Curie temperature ( T C ) using the Heisenberg model is 104 K, which is in agreement with the experimentally observed value of 94/97 K. Interestingly, an insulator-to-metal transition is achieved at a critical compressive strain of -6% with a robust FiM state, where the Co 3d xy and Ir 5d x 2 - y 2 orbitals are mainly responsible for metallicity. Simultaneously, the magnetocrystalline anisotropy energy and T C can be sufficiently enhanced by applying compressive strain due to enhancement in the structural distortions. So this work suggested that the strain strategy is an efficient approach to tuning the properties of the compounds for their feasible realization in spintronics.