Exploring orders in new double double perovskites

Perovskites ABO3 are important for many properties. Cation orderings can give double perovskites (DPv) and double double perovskites (DDPv = AA’BB’O6). Using high pressure-temperature synthesis, we discovered a new type of DDPv. We propose to study two further materials; 1. CaFeFeNbO6 – the first Fe-based DDPv. All previously reported DDPvs were Mn-based so CaFeFeNbO6 is an exciting development. WISH data are needed to investigate spin orders below 11 and 250 K transitions, and to measure O coordinates so BVS’s can be used to measure Fe2+/Fe3+ intersite charge transfer. 2. CaMnCoWO6 – the role of Mn/Co disorder. CaMnMnWO6 can be switched cleanly from a DDPv to a DPv polymorph leading to a switch in magnetic properties. We have subsequently prepared this new analogue - WISH PND data are needed to investigate spin order below 20 K and determine Mn/Co anti-site disorder - an extra variable.