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

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

Campinas

Congreso; XXII Reunión Anual de Usuarios del LNLS; 2012

LNLS

Since the magnetoresistance effect (MR) was discovered in spinel?type compounds, these have been the subject of renewed studies in the field of material sciences. Although theirMR is not as marked as that of some perovskites, spinel?type materials are attractive candidates for MR materials because a great number of spinels have ferrimagnetic properties and display some kind of electrical conductivity. Consequently, the search for magnetic spinels which might present MR effect has of technological importance. Materials belonging to thespinel family have the stoichiometry AB2X4, where A and B are cations of either 2+ and 3+ charge or of 4+ and 2+ charge, and X represents O2¡ or chalcogenides (like S2¡ and Te2¡).The structure is based on the cubic close?packing of anions with the cations located in 1/8 of the tetrahedral (T) and 1/2 of the octahedral (O) sites. In this work the chemical environmentsof Mn in spinel?type oxides Mn(2¡x)V(1+x)O4 (x = 0, 1/3 and 1) were studied using conventional X?ray absorption spectroscopy (XAS) technique. In addition, Mn-K XANESspectra were used to compare and validate the results obtained with high?resolution Kb emission spectroscopy (XES).