Room-temperature ferromagnetism in the mixtures of the TiO2 and Co3O4 powders
A. Serrano, E. Fernandez Pinel, A. Quesada, I. Lorite, M. Plaza, L., Perez, F. Jimenez-Villacorta, J. de la Venta, M. S. Martin-Gonzalez, J. L., Costa-Kramer, J. F. Fernandez, J. Llopis, M. A. Garcia
TL;DR
This study demonstrates room-temperature ferromagnetism in TiO2 and Co3O4 powder mixtures, linked to surface reduction of cobalt ions, with the effect dependent on TiO2's crystal structure.
Contribution
It reveals ferromagnetism in TiO2-Co3O4 mixtures at room temperature and identifies surface cobalt reduction as the cause, highlighting the importance of TiO2's anatase phase.
Findings
Ferromagnetism observed at 300 K in TiO2 and Co3O4 mixtures.
Surface reduction of Co+3 to Co+2 correlates with magnetism.
Anatase TiO2, not rutile, exhibits this ferromagnetic behavior.
Abstract
We report here the observation of ferromagnetism (FM) at 300 K in mixtures of TiO2 and Co3O4 powders despite the antiferromagnetic and diamagnetic character of both oxides respectively. The ferromagnetic behavior is found in the early stages of reaction and only for TiO2 in anatase structure; no FM is found for identical samples prepared with rutile-TiO2. Optical spectroscopy and X-ray absorption spectra confirm a surface reduction of octahedral Co+3->Co+2 in the mixtures which is in the origin of the observed magnetism
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