Magnetic and structural studies of the double perovskites Ba2REMoO6

A magnetic, electronic and structural study of the double perovskites Ba2REMoO6 (RE=Sm, Eu, Gd, Dy) has been performed. All materials crystallise in the cubic Fm3¯m symmetry space group and the cell volume decreases as RE varies from Sm to Dy in accordance with Vegard's law. An antiferromagnetic transition is observed below TN=130 and 112 K for RE=Sm and Eu, respectively. The Néel temperatures of these ordered rare earth molybdenum double perovskites are much higher than previously observed in double perovskites containing Eu or Sm and a 4d or 5d transition metal arranged in an ordered rock salt configuration. The high Néel temperatures arise due to a strong superexchange magnetic interaction via the Mo-O-RE-O-Mo pathway. All of the phases are electronically insulating and there is no evidence of magnetoresistance at any temperature.