The oxide, Mn0.6Ta0.4O1.65, was synthesized in air by rapidly cooling a melt from 1400C. It was characterized by using X-ray powder diffraction, selected-area electron diffraction, high-resolution electron microscopic, thermal analysis, magnetic susceptibility and electrical conductivity techniques. The average structure was that of a cubic fluorite, with a = 0.49826nm and with 18% vacancies on O-atom sites. Prominent diffuse scattering was seen in its electron diffraction patterns, and a structural model for this scattering was proposed. It was based upon roughly 1nm-sized micro-domains, with a pyrochlore-type structure, which were separated by antiphase boundaries. The magnetic susceptibility data revealed an antiferromagnetic interaction between the Mn2+ ions and an effective number of Bohr magnetons that increased with temperature.

An Electron and X-Ray Powder Diffraction Study of the Defect Fluorite Structure of (Mn,Ta)O2. S.Esmaeilzadeh, J.Grins, A.K.Larsson: Journal of Solid State Chemistry, 1999, 145[1], 37-49