Structural and magnetic study of the cation-ordered perovskites Ba2xSrxErMoO6

摘要

A series of perovskite phases have been prepared from the appropriate carbonates and oxides by heating under reducing conditions at temperatures up to 1300 degrees C. Complete ordering between ErO6 and MoO6 octahedra and a disordered distribution of Sr2+ and Ba2+ occur in all compounds. Neutron powder diffraction experiments show that the substitution of Sr2+ into Ba2ErMoO6 introduces a progressive reduction in symmetry from Fm3m (x = 0) to I4/m (x = 0.5, 0.8) to P2(1) (x = 1.25, 1.75, 2.0). Magnetic susceptibility measurements indicate that all of these compounds show Curie-Weiss paramagnetism and that for x < 1.25 this behaviour persists down to 2 K. The monoclinically distorted compounds show magnetic transitions at low temperature and neutron diffraction has confirmed the presence of long-range antiferromagnetic order below 2.5 and 4K in Ba0.25Sr1.75ErMoO6 and Sr2ErMoO6, respectively. Ba0.75Sr1.25ErMoO6, Ba0.25Sr1.75ErMoO6 and Sr2ErMoO6 do not undergo structural distortion on cooling from room temperature. (c) 2006 Elsevier Inc. All rights reserved.