Damping of antiferromagnetic spin waves by valence fluctuations in the double layer perovskite YBaFe2O5.
Inelastic neutron scattering experiments show that spin dynamics in the charge-ordered insulating ground state of the double layer perovskite YBaFe(2)O(5) is well described in terms of e(g) superexchange interactions. Above the Verwey transition at T(V)=308 K, t(2g) double exchange-type conduction proceeds within antiferromagnetic FeO(2)-BaO-FeO(2) double layers by an electron hopping process that requires a spin flip of the five-coordinated Fe ions, costing an energy of 5<J>S(2) approximately 0.1 eV. The hopping process disrupts near-neighbor spin correlations, leading to massive damping of zone-boundary spin waves.
Ames Laboratory, Ames, Iowa 50011, USA. schang@ameslab.gov
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