Large Magnetocrystalline Anisotropy and Giant Coercivity in the Ferrimagnetic Double Perovskite Lu2NiIrO6

We discover that large uniaxial magnetocrystalline anisotropy driven by the simultaneous presence of spin–orbit coupling and structural distortions is the origin of the giant coercivity observed experimentally in the double perovskite Lu2NiIrO6. The magnetic easy axis turns out to be the monoclinic b-axis with an anisotropy constant as high as 1.9 × 108 erg/cm3. The predicted coercive field of 50 kOe and Curie temperature of 220 K agree with the experimentally observed values and point to potential of Lu2NiIrO6 in spintronics applications. We find that the spin–orbit coupling induces a rare Ir4+ Jeff = 1/2 Mott insulating state, suggesting that Lu2NiIrO6 provides a playground to study the interplay between spin–orbit coupling and electronic correlations in a 5d transition metal oxide. The spin–orbit coupling also results in a direct band gap with the valence and conduction states localized on different transition metal sublattices, i.e., efficient electron–hole separation upon photoexcitation and low electron–hole recombination.