Switching from ferro- to antiferromagnetism in A2CrSbO6 (A = Ca, Sr) double perovskites: a neutron diffraction study

Abstract

Double perovskites Sr2CrSbO6 and Ca2CrSbO6 have been prepared by a solid-state procedure. The crystal and magnetic structures have been studied from X-ray (XRD) and neutron powder diffraction (NPD) data. Rietveld refinements show that the room-temperature crystal structure is monoclinic (space group P21/n), and contains an almost completely ordered array of alternating CrO6 and SbO6 octahedra sharing corners, tilted along the three pseudocubic axes according to the Glazer notation a−a−b+. The monoclinic distortion is larger in Ca2CrSbO6 than in Sr2CrSbO6, which is associated with the tilting of the CrO6 and SbO6 octahedra, displaying tilting angles φ = 13.5° and φ = 5.5°, respectively. Magnetization measurements and low-temperature NPD data show that Sr2CrSbO6 is an antiferromagnet with a Néel temperature of 12 K with an ordered magnetic moment of 1.64(4) μB per Cr3+. The propagation vector is k = 0. Ca2CrSbO6 exhibits ferromagnetic long-range order below TC = 16 K, with a saturation magnetization of 2.36 μB at 5 K. In the ferromagnetic arrangement, the Cr3+ spins are aligned approximately along the [110] direction with an ordered magnetic moment of 2.6(2) μB. To our knowledge, this is the first example of a ferromagnetic double perovskite containing a non-magnetic element in the B positions of the perovskite structure.