Neutron diffraction study and magnetotransport properties of stoichiometric CaMoO3 perovskite prepared by a soft-chemistry route

Polycrystalline CaMoO3 perovskite has been prepared by soft-chemistry procedures, followed by controlled annealing under reducing conditions (H-2/N-2 flow). The crystal structure, studied from neutron powder diffraction data, can be described in an orthorhombic unit cell, space group Pbnm (No. 62). The lattice parameters were a = 5.4510(1) angstrom, b = 5.5821 (1) angstrom and c = 7.7803(2) angstrom. In the perovskite network the MoO6 octahedra are tilted by 13.5 degrees in order to optimize the Ca-O bond lengths; the tilting scheme corresponds to a GdFeO3-like superstructure. The perovskite is fully oxygen stoichiometric, as demonstrated from the refinement of the oxygen occupancy factors. Resistivity and transport measurements indicated that CaMoO3 behaves as a metal; at low temperatures (5 K) a small positive magnetoresi stance is observed, reaching a maximum value of 1.4% at 9 T. The magnetic susceptibility is predominantly Pauli paramagnetic-like, although a non-negligible temperature-dependent component due to isolated Mo4+ spins is patent at low temperatures. (c) 2006 Elsevier Inc. All rights reserved.