Half-metallic ferromagnetism in non-magnetic double perovskite oxides Sr2MSbO6 (M=Al, Ga) doped with C and N

Double perovskite oxides have gained tremendous attention in material science and device technology due to their facile synthesis and exceptional physical properties. In this paper, we elucidate the origin of magnetisation in non-magnetic double perovskite oxides Sr2MSbO6 (M = Al, Ga) induced by non-magnetic 2p impurities (C and N) substituted. The calculations were done within the full potential linearised augmented plane wave method in the framework of the density functional theory. The exchange-correlation potential is evaluated using the generalised gradient approximation (GGA) of Perdew-Burke-Ernzerhof and the modified Becke and Johnson (mBJ-GGA). Regarding structural properties of undoped double perovskites Sr2MSbO6 (M = Al, Ga), we found that the lattice constants and oxygen positions are in rational accord with the experimental results. Furthermore, both of the examined compounds are brittle in nature with isotropic character. For Sr2AlSbO6, we have got the values of energy gap equal to 1.9 and 3.7 eV within the GGA and the mBJ-GGA, respectively. However, for Sr2GaSbO6 the values of energy gap obtained in GGA and mBJ-GGA are equal to 0.8 and 2.9 eV, respectively. Finally, spin-polarised calculations reveal that the doping C and N can lead to drastic changes in the magneto-electronic properties of the semiconducting Sr2MSbO6 matrix with the integer magnetic moment of 6.00 mu(B) and exhibit half-metallic properties. The origin of ferromagnetism can be attributed to the spin-split impurity bands inside the energy gap of the semiconducting Sr2MSbO6 matrix. These results may help experimentalists in synthesising new double perovskites for spintronic applications.