Ferromagnetic Mott-Insulating State in Double Perovskites Gd2MgIrO6

We have studied the electronic and magnetic properties of double perovskites Gd2MgIrO6 by first-principles density functional theory (DFT). Based on the DFT calculations, Gd2MgIrO6 is found to have a ferromagnetic (FM) ground state. The material undergo half-metallic ferromagnets to Mott-Hubbard insulator transition which happens due to strong correlation in Gd-4f and Ir-5d states. Our results shows that the 5d electrons of Ir hybridize strongly with O-2p states near the Fermi level giving rise to the insulating state of Gd2MgIrO6. Our study suggests that the enhanced magnetic moment is a result of itinerant exchange rather than the exchange interaction involving individual ions of Gd and Ir atoms. The total magnetic moment calculated in the present studies is 15 {\mu}B per formula unit for Gd2MgIrO6.