La3+ doping of the Sr2CoWO6 double perovskite: A structural and magnetic study

Abstract

La-doped Sr2CoWO6 double perovskites have been prepared in air in polycrystalline form by solid-state reaction. These materials have been studied by X-ray powder diffraction (XRPD), neutron powder diffraction (NPD) and magnetic susceptibility. The structural refinement was performed from combined XRPD and NPD data (D2B instrument, λ=1.594 Å). At room temperature, the replacement of Sr2+ by La3+ induces a change of the tetragonal structure, space group I4/m of the undoped Sr2CoWO6 into the distorted monoclinic crystal structure, space group P21/n, Z=2. The structure of La-doped phases contains alternating CoO6 and (Co/W)O6 octahedra, almost fully ordered. On the other hand, the replacement of Sr2+ by La3+ induces a partial replacement of W6+ by Co2+ into the B sites, i.e. Sr2-xLaxCoW1-yCoyO6 (y=x/4) with segregation of SrWO4. Magnetic and neutron diffraction measurements indicate an antiferromagnetic ordering below TN=24 K independently of the La-substitution.