Nonadiabatic small polarons, positive magnetoresistance, and ferrimagnetism behavior in the partially inverse Mn2−xV1+xO4 spinels

E. V. PANNUNZIO-MINER; J. M. DE PAOLI; R. E. CARBONIO; R. D. SANCHEZ

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Año: 2009 vol. 105 p. 1139061 - 1139069

0021-8979

We present experimental results of electrical resistivity, magnetoresistance (MR), Seebeckcoefficient (S), and magnetic susceptibility (X) experiments at high temperature on the spinelMn2−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 r indicates the presence of small polarons and the temperature dependence of r is well fitted with the nonadiabatic polarons model. All the samples present positive MR at room temperature, in particular, the highest value around 1% was observed in the MnV2O4 sample.