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. CEPPI; A. MESQUITA; F. POMIRO; E.V.PANNUNZIOMINER

Campinas

Congreso; XXII Reunión Anual de Usuarios del LNLS; 2012

The spinel Mn2¡xV1+xO4 series with x = 0; 1=3, and 1, prepared by solid statereaction, were studied by Pannunzio-Miner et al. 1 using several techniques inorder 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 tetrahedraland 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 weremeasurement at the D04B-XASF1 beamline. The Mn oxidation state and coordi-nation were determined using the edge energy half way up the normalized-edgestep in the usual way (i.e. where the absorption is equal to 0.5) and the area ofthe extracted pre-edge structure, respectively, comparing with reference spinels. Inaddition, these results were used to compare this conventional technique with thehigh-resolution K¯ Emission Spectroscopy applied in previous works 2;3.