title: Total neutron scattering investigation of the structure of a cobalt gallium oxide spinel prepared by solvothermal oxidation of gallium metal.
abstract: A new solvothermal synthesis route to mixed-metal gallium oxides with the spinel structure has been developed for ternary oxides of ideal composition Ga(3-x)M(x)O(4-y) (M=Co, Zn, Ni). The structure of the novel cobalt gallate produced in this manner, Ga(1.767(8))Co(0.973(8))O(3.752(8)), has been determined from total neutron scattering to be a partially defective spinel with mixed-valent cobalt (approximately 25% Co(3+) and 75% Co(2+)) and with vacancies on approximately 6% of oxygen sites. Pair distribution function (PDF) analysis reveals significant local deviations from the average cubic structure, which are attributed to the conflicting coordination preferences of the Co(2+) (potential Jahn-Teller distortion) and Ga(3+) (Ga off-centring). Reverse Monte Carlo (RMC) modelling supports this conclusion since different metal-oxygen bond-distance distributions are found for the two cations in the refined configuration. An investigation of magnetic properties shows evidence of short-range magnetic order and spin-glass-like behaviour, consistent with the structural disorder of the material.
authors.affiliation: Department of Chemistry, University of Warwick, Coventry, West Midlands, CV4 7AL, UK. Department of Physics, University of Warwick, Coventry, West Midlands, CV4 7AL, UK.
authors.forename: Helen Y
authors.initials: HY
authors.lastname: Playford
authors.forename: Alex C
authors.initials: AC
authors.lastname: Hannon
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Tucker
authors.forename: Martin R
authors.initials: MR
authors.lastname: Lees
authors.forename: Richard I
authors.initials: RI
authors.lastname: Walton