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Title: Magnetocrystalline interactions and oxidation state determination of Mn{sub (2−x)}V{sub (1+x)}O{sub 4} (x=0, 1/3 and 1) magnetorresistive spinel family

Oxidation states of transition metal cations in spinels-type oxides are sometimes extremely difficult to determine by conventional spectroscopic methods. One of the most complex cases occurs when there are different cations, each one with several possible oxidation states, as in the case of the magnetoresistant Mn{sub (2−x)}V{sub (1+x)}O{sub 4} (x=0, 1/3 and 1) spinel-type family. In this contribution we describe the determination of the oxidation state of manganese and vanadium in Mn{sub (2−x)}V{sub (1+x)}O{sub 4} (x=0, 1/3,1) spinel-type compounds by analyzing XANES and high-resolution Kβ X-ray fluorescence spectra. The ionic models found are Mn{sup 2+}{sub 2}V{sup 4+}O{sub 4}, Mn{sup 2+}{sub 5/3}V{sup 3.5+}{sub 4/3}O{sub 4} and Mn{sup 2+}V{sup 3+}{sub 2}O{sub 4}. Combination of the present results with previous data provided a reliable cation distribution model. For these spinels, single magnetic electron paramagnetic resonance (EPR) lines are observed at 480 K showing the interaction among the different magnetic ions. The analysis of the EPR parameters show that g-values and relative intensities are highly influenced by the concentration and the high-spin state of Mn{sup 2+}. EPR broadening linewidth is explained in terms of the bottleneck effect, which is due to the presence of the fast relaxing V{sup 3+} ion instead of the weakmore » Mn{sup 2+} (S state) coupled to the lattice. The EPR results, at high temperature, are well explained assuming the oxidation states of the magnetic ions obtained by the other spectroscopic techniques. - Graphical abstract: View of the crystallographic structure of a spinel. It shows as an example one of the models of ion distribution determined for the spinels Mn{sub (2−x)}V{sub (1+x)}O{sub 4} (x=0, 1/3,1). Display Omitted - Highlights: • Determination of oxidation state of the metallic ions in Mn{sub (2−x)}V{sub (1+x)}O{sub 4} (x=0,1/3,1) by XAS and XES techniques. • The ionic models found are Mn{sup 2+}{sub 2}V{sup 4+}O{sub 4}, Mn{sup 2+}{sub 5/3}V{sup 3.5+}{sub 4/3}O{sub 4} and Mn{sup 2+}V{sup 3+}O{sub 4}. • EPR spectra correspond almost exclusively to a resonance of Mn{sup 2+}.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [2] ;
  1. INFIQC-CONICET, Departamento de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina)
  2. IFEG-CONICET and Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina)
  3. Centro Atómico Bariloche, Comisión Nacional de Energía Atómica e Instituto Balseiro, Universidad Nacional de Cuyo, 8400 San Carlos de Bariloche (RN) (Argentina)
  4. Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, 13506-900 Rio Claro, São Pablo (Brazil)
Publication Date:
OSTI Identifier:
22280726
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 205; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; CATIONS; CRYSTALLOGRAPHY; DISTRIBUTION; ELECTRON SPIN RESONANCE; FLUORESCENCE; FLUORESCENCE SPECTROSCOPY; HIGH SPIN STATES; INTERACTIONS; MANGANESE; MANGANESE IONS; SPECTRA; SPINELS; VANADIUM; VANADIUM IONS; X RADIATION; X-RAY SPECTROSCOPY