Mn coordination and oxidation state determination in spinel Mn(2-x)V(1+x)O4 series by XANES. Comparison with high resolution Kb emission spectroscopy

G. TIRAO; S. A. CEPPI; A. MESQUITA; F. POMIRO; E. V. PANNUNZIO MINER

Campinas

Congreso; 22º Reunión anual de usuarios; 2012

LNLS

The spinel Mn(2−x)V(1+x)O4 series with x = 0, 1/3, and 1, prepared by solid state reaction, were studied by Pannunzio-Miner et al. using several techniques in order to explain their magnetic susceptibility and electrical properties behaviors. All the samples presented positive magnetoresistance (MR) at room temperature, in particular, the highest value (around 1%) was observed in the MnV2O4 sample. This feature could be justify by the distribution of Mn/V cations in the tetrahedral and octahedral sites, assuming that the Mn and V cations were in the 2+ and 3+ oxidation states, respectively. In order to study the Mn chemical environment, Mn-K XANES spectra were measurement at the D04B-XASF1 beamline. The Mn oxidation state and coordination were determined using the edge energy half way up the normalized-edge step in the usual way (i.e.where the absorption is equal to 0.5) and the area of the extracted pre-edge structure, respectively, comparing with reference spinels. In addition, these results were used to compare this conventional technique with the high-resolution Kb Emission Spectroscopy applied in previous works.