Structure and magnetic properties of cation-disordered perovskites SrLaCrSnO6 and Ca2CeCr2TiO9

Polycrystalline samples of the new perovskites SrLaCrSnO6 and Ca2CeCr2TiO9 have been synthesised using the ceramic method and characterized by x-ray diffraction, neutron diffraction and magnetometry. Both crystallise in the space group Pbnm, with a disordered distribution of B-site cations, and both exhibit Gz-type antiferromagnetism at low temperatures. The antiferromagnetic order develops over a large temperature range. It is proposed that isolated antiferromagnetic clusters grow in size upon cooling to form a long-range antiferromagnetically-ordered backbone running through the structure. Cations with few magnetic nearest-neighbours remain decoupled from the backbone down to 2 K. More decoupled clusters are present in Ca2CeCr2TiO9 than in SrLaCrSnO6. This is attributed to the increase in frustration that accompanies the increase in strength of the next-nearest-neighbour interactions that occurs when d10:Sn4+ is replaced by d0:Ti4+