Electronic structure and estimation of Curie temperature in Ca\u3csub\u3e2\u3c/sub\u3eBIrO\u3csub\u3e6\u3c/sub\u3e(B = Cr, Fe) double perovskites

We investigate the electronic and magnetic properties of Ca 2 CrIrO 6 and Ca 2 FeIrO 6 by means of density functional theory. These materials belong to a family of recently synthesized Ca 2 CrOsO 6 whose properties show possible applications in a room temperature regime. Upon replacement of Os by Ir in Ca 2 CrOsO 6, we found the system to exhibit a stable ferrimagnetic configuration with a bandgap of ∼0.25 eV and an effective magnetic moment of ∼2.58 μ B per unit cell. Furthermore, when chemical doping is considered by replacing Cr with Fe and Os with Ir, the material retains the insulating state but with a reduced bandgap of 0.13 eV and large increment in the effective magnetic moment of ∼6.68 μ B per unit cell. These observed behaviors are noted to be the consequence of the cooperative effect of spin-orbit coupling; Coulomb correlations from Cr-3d, Fe-3d, and Ir-5d electrons; and the crystal field effect of the materials. These calculations suggest that by chemical tuning, one can manipulate the bandgap and their effective magnetic moment, which may help in material fabrication for device applications. To check further the suitability and applicability of Ca 2 CrIrO 6 and Ca 2 FeIrO 6 at higher temperatures, we estimate the Curie temperature (T C) by calculating the spin-exchange coupling. We found that our findings are in a valid T C trend similar to other perovskites. Our findings are expected to be useful in experimental synthesis and transport measurement for potential applications in modern technological devices