Paramagnetism and clustering in Fe-doped TiO2 nanoparticles

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Abstract

The magnetic behavior of Fe-doped TiO2 anatase nanoparticles (2.8 and 5.4 at.%) was investigated throughout magnetizations versus applied field measurements between 2 and 300 K temperatures. The experimental results were well-fitted by using the Brillouin function, giving rise to a moment per isolated Fe atom of about 5 μB. The thermal evolution of the number of magnetic ions shows that a decrease of ions in paramagnetic state occurs below 50 K for the most diluted sample. However for the 5.4 at.% sample the fall even at room temperature is evident. These moments probably order antiferromagnetically via superexchange interactions. Taking into account the low concentration of dopant and the high fraction of interacting ions, a correlated substitution of Fe in cation sites of TiO2 structure needs to be considered.

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Acknowledgements

We appreciate the financial support of CONICET, Argentina (PIP 6005 and PIP 6075). The DC magnetic measurements were performed using the RN3M facilities. We thank F.H. Sánchez for helpful discussions.

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