We collaborate with other groups in the characterization of complex oxides:

• With Frank Berry and collaborators from the Department of Chemistry, University of Birmingham (UK), we have synthesized and characterized new complex transition metal oxides with different structures. In particular, we have studied the magnetic properties, the oxidation state of the cations and the different structural properties of FeSb₂O₄, which is isostructural with Pb₃O₄, and some lead- and cobalt-doped variants of composition FeSb1.5Pb0.5O4 and Co_0.5Fe_0.5Sb_1.5Pb_0.5O₄. We have found that antimony is present as Sb³⁺ and that the presence of Pb²⁺ on the antimony site induces partial oxidation of Fe²⁺ to Fe³⁺.The results have shown that there is no Verwey-type transition in which electrons are shared between iron in different oxidation states and that the quasi-one-dimensional magnetic structure gives rise to situations in which weakly coupled Fe²⁺ ions can coexist in a non-magnetic state alongside Fe³⁺ ions in a magnetically ordered state. Further work comprises the study initiated in previous years on the effect that the fluorination of compounds of the type Sr₃Fe₂O_7-x exerts on the cationic distribution and the complex magnetic properties of these materials.
• As part of a collaboration with Juan Luis Gautier and collaborators (Department of Materials Chemistry, University of Santiago de Chile), that has spread over the past fifteen years through bilateral cooperation projects we have studied compounds of composition LiNi_xCo_2-xO₄ , which are of interest in the field of Li-ion batteries, and which have been synthesized via sol gel procedures at low temperature. By means of X-ray photoelectron spectroscopy, XPS, we have found that a fraction of the Co ions in these compounds is present in the relatively unusual oxidation state of Co⁴⁺.