Neutron diffraction study and magnetotransport properties of stoichiometric CaMoO 3 perovskite prepared by a soft-chemistry route

Abstract

Polycrystalline CaMoO 3 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) Å, b=5.5821(1) Å and c=7.7803(2) Å. In the perovskite network the MoO 6 octahedra are tilted by 13.5° in order to optimize the Ca–O bond lengths; the tilting scheme corresponds to a GdFeO 3-like superstructure. The perovskite is fully oxygen stoichiometric, as demonstrated from the refinement of the oxygen occupancy factors. Resistivity and transport measurements indicated that CaMoO 3 behaves as a metal; at low temperatures (5 K) a small positive magnetoresistance 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 Mo 4+ spins is patent at low temperatures.