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 P2(1)/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. (c) 2010 Elsevier Inc. All rights reserved