Local structure study of Mn and V in spinel Mn(2-x)V(1+x)O4 series by high-resolution Kb emission spectroscopy

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

Campinas

Congreso; 21ª Reunião Anual de Usuários do LNLS; 2011

LNLS

In the first row transition metals, high resolution X-ray Kb spectra consist of main lines (Kb1,3, Kb5) and satellite lines (Kb´ , Kb´´) whose origin are related to spin coupling of 3p and 3d electrons or to ligand type. Relative variations of spectral parameters in diferent compounds are useful to characterize the main atom chemical environment, i.e., the oxidation states, the net spin in the valence band, and the occupation site. Kb spectra and their relation with the chemical environment have been quite studied for Mn compounds and less for V compounds 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 5%) was observed in the MnV2O4 sample. The electrical and magnetic transport was explained using a model of cation distribution where manganese was present as Mn2+ and vanadium as V3+ or V4+, depending on the compound stoichiometry 5. In this work, measurements of the V-Kb and Mn-Kb X-ray emission spectra were performed using a high-resolution Johann-type spectrometer 8 at the D12A-XRD1 beamline at the LNLS. The spectral parameters dependences founded show that the Mn (V) atoms are in 2+ (3+ / 4+) oxidation states preferentially located at tetrahedral (octahedral) site. This results confirm the MR magnetic model of spinel Mn(2-x)V(1+x)O4 series.