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

GERMÁN TIRAO; SERGIO CEPPI; ALEXANDER MESQUITA; FERNANDO POMIRO; ELISA VICTORIA PANNUNZIO MINER

Campinas

Congreso; 22 Reunión Anual de usuarios del Laboratorio Nacional de Luz Sincrotrón; 2012

LNLS, Caminas, Brasil

The spinel Mn2¡xV1+xO4 series with x = 0; 1=3, and 1, prepared by solid state reaction, were studied by Pannunzio-Miner et al. 1 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 coordi- nation 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 K¯ Emission Spectroscopy applied in previous works