Structure distortion and magnetism in double perovskites Ca2−xLaxFeReO6 (0≤x≤0.8)

The crystal structure and magnetism of Ca2−xLaxFeReO6 (0≤x≤0.8) double perovskites have been investigated. The samples with low doping (x≤0.4) are found to crystallize with the monoclinic P21/n superstructure, while those in the high doping ones (x≥0.6) have orthorhombic Pbnm superstructure. With the increase of an La doping, the anti-site defects increases, giving rise to highly disordered samples at the Fe and Re positions. At the low doping region (x≤0.4), the compounds undergo a simultaneous structural and magnetic transition accompanying a slight increase of the Curie temperature. The increase of Curie temperature is discussed in terms of the structural change with doping.