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arXiv · 0707.2253

Zener double exchange from local valence fluctuations in magnetite

R. J. McQueeney·M. Yethiraj·S. Chang·W. Montfrooij·T. G. Perring·J. Honig·P. Metcalf
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Abstract

Magnetite (Fe$_{3}$O$_{4}$) is a mixed valent system where electronic conductivity occurs on the B-site (octahedral) iron sublattice of the spinel structure. Below $T_{V}=122$ K, a metal-insulator transition occurs which is argued to arise from the charge ordering of 2+ and 3+ iron valences on the B-sites (Verwey transition). Inelastic neutron scattering measurements show that optical spin waves propagating on the B-site sublattice ($\sim$80 meV) are shifted upwards in energy above $T_{V}$ due to the occurrence of B-B ferromagnetic double exchange in the mixed valent metallic phase. The double exchange interaction affects only spin waves of $Δ_{5}$ symmetry, not all modes, indicating that valence fluctuations are slow and the double exchange is constrained by electron correlations above $T_{V}$.

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R. J. McQueeney, M. Yethiraj, S. Chang, W. Montfrooij, T. G. Perring, J. Honig, P. Metcalf. 2007-07-16. Zener double exchange from local valence fluctuations in magnetite. https://doi.org/10.1103/physrevlett.99.246401

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