Electron doping in the double perovskite LaxA2-xCrWO6 with A=Sr and Ca

The ferrimagnetic double perovskites can have high Curie temperatures T-C above 600 K. In the system Sr2FeMoO6 (T-C approximate to 420 K) electron doping by substituting, for example, La3+ for Sr2+ ions leads to a considerable increase in T-C. Here we report the same effect for LaxCa2-xCrWO6. This demonstrates that electron doping generically increases T-C in the ferrimagnetic double perovskites. However, in the system Sr2CrWO6 (T-C approximate to 450 K) the preferential formation of LaCrO3 prevents electron doping by La substitution as supported by neutron scattering and x-ray diffraction. (C) 2006 American Institute of Physics.