Fig. 1: Crystal structures and schematic energy level diagram.

Crystal structure of a cubic space group Fm-3m (No. 225) and b tetragonal space group I4/m (No. 87) double perovskites. c Schematic energy level diagram of the d-levels in the cubic octahedron crystal field at the 3d B and 4d/5d B' sites. The arrows indicate the direction of magnetic moment at the B and B' magnetic sites.