Non-adiabatic small polarons, positive magnetoresistance and ferrimagnetism behavior in the partially inverse Mn2-xV1+xO4 spinels.

J.M. DE PAOLI

JOURNAL OF APPLIED PHYSICS

The American Institute of Physics

Lugar: Argonne; Año: 2009 vol. 105

0021-8979

e present experimental results of electrical resistivity (ρ), magnetoresistance (MR), Seebeck coefficient (S), and magnetic susceptibility (χ) experiments at high temperature on the spinel Mn2-xV1+xO4 series with x=0, 1/3 and 1, prepared by solid state reaction. The Rietveld analysis of neutron powder diffraction (NPD) patterns confirm the expected cubic symmetry (SG: Fd-3m) with cell parameters, around 8.5 Å. We also precisely calculate the distribution of Mn/V cations, in the tetrahedral and octahedral sites, for the whole series showing an important degree of inversion. The magnetic susceptibility and electrical transport properties show ferrimagnetic and semiconductor behaviors respectively. A large difference detected between the activation energies for S and ρ indicates the presence of small polarons and the temperature dependence of ρ is well fitted with the non-adiabatic polarons model. All the samples present ositive magnetoresistance (MR) at room temperat