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 P2(1)/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 (CaCrSbO6)-Cr-2 than in Sr2CrSbO6, which is associated with the tilting of the CrO6 and SbO6 octahedra, displaying tilting angles phi = 13.5 degrees and phi = 5.5 degrees, respectively. Magnetization measurements and low-temperature NPD data show that Sr2CrSbO6 is an antiferromagnet with a Neel temperature of 12 K with an ordered magnetic moment of 1.64(4) mu(B) 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 mu(B) at 5 K. In the ferromagnetic arrangement, the Cr3+ spins are aligned approximately along the  direction with an ordered magnetic moment of 2.6(2) mu(B). 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.
- POWDER DIFFRACTION