Evolution of metallicity, enhancement of TC and magnetic anisotropy energy in Y2NiIrO6: Hydrostatic ([111]) strain influence

Ir-based double perovskite oxides (DPO) provide a distinct electronic and magnetic behavior due to entanglement among lattice distortion, strong electron correlation, and spin–orbit coupling (SOC). In this work, we investigated the hydrostatic ([111]) strain impact on the physical properties of the Y${}_2$NiIrO${}_6$ DPO using ab-initio calculations. Unstrained motif displayed the ferrimagnetic (FiM) spin state owing to strong antiferromagnetic (AFM) interactions between Ni$\uparrow$ and Ir$\downarrow$ ions, further confirmed by the computed partial spin magnetic moments and 3D spin-magnetization density iso-surfaces plots. A Mott-insulating state is established with an energy band gap ($E_g$) of 0.43 eV due to the existence of a rare Ir${}^{+4}$ state having $J_{eff.}=\frac{1}{2}$ and a Curie temperature ($T_C$) of 198 K using the Heisenberg Hamiltonian model, which is up to the experimental observations. The easy magnetic axis is the [010] (b-axis) having a giant magnetic anisotropy energy (MAE) constant of 1.7 × 10${}^8$ erg/cm${}^3$. Moreover, it is predicted that strain holds the FiM spin order as a magnetic ground state for the considered range of $\pm$8%. Notably, an electronic transition from Mott-insulating to a metallic state is established at a critical compressive strain of $-$8%, where the admixture of Ir 5d states appears at/around the Fermi level. On the other hand, $E_g$ solely increases with the increase of tensile strain amplitude. Due to strong and weak hybridization, the spin/orbital magnetic moment value is reduced and enhanced as a function of compressive and tensile strains, respectively. Along with this, it is found that MAE/$T_C$ increases to 25%/18% and 15%/10% at $-$8% compressive and ＋8% tensile strains due to larger structural distortion than that of the unstrained one, which enhances the system potential for magnetic memory devices.