Preparation, crystal structure, and magnetic and magnetotransport properties of the double perovskite Ca2FeMoO6

Ca2FeMoO6 perovskite has been prepared in polycrystalline form by controlle d reduction of previously decomposed citrate precursors. This material has been studied by X-ray and neutron powder diffraction (NPD), scanning electr on microscopy, thermal analysis, and magnetic and magnetotransport measurem ents. The crystal structure is monoclinic, space group P2(1)/n, with a = 5. 4150(1), b = 5.5224(1.), c = 7.7066(2) Angstrom, and beta = 89.969(8)degree s at room temperature (RT). The crystal contains alternating FeO6 and MoO6 octahedra, considerably tilted due to the relatively small size of the Ca2 cations. Low-temperature (2 K) NPD data show evidence for a ferrimagnetic coupling between the Fe3+ and Mo5+ sublattices, with ordered magnetic momen ts of 3.2(1) and -0.76(6) mu(B), respectively. The Curie temperature is 380 K. Both magnetism and transport indicate a large component of itinerancy f or downspin Feta, electrons. The carrier density measured by the Hall effec t is 0.031 holes per formula unit at 100 K. A magnetoresistance of 80% has been observed at RT for 9T, significantly larger than that reported for oth er A(2)FeMoO(6) perovskites, A = Sr, Ba.