Damping of antiferromagnetic spin waves by valence fluctuations in the double layer perovskite YBaFe2O5

TL;DR

This study investigates how valence fluctuations in YBaFe2O5 dampen antiferromagnetic spin waves, revealing that electron hopping processes disrupt spin correlations and cause significant damping of spin excitations.

Contribution

It provides experimental evidence linking valence fluctuations to spin wave damping in a double-layer perovskite, highlighting the role of electron hopping in magnetic dynamics.

Findings

Spin dynamics are well described by eg superexchange interactions.

Electron hopping disrupts spin correlations above the Verwey transition.

Valence fluctuations cause massive damping of zone-boundary spin waves.

Abstract

Inelastic neutron scattering experiments show that spin dynamics in the charge ordered insulating ground state of the double-layer perovskite YBaFe2O5 is well described in terms of eg superexchange interactions. Above the Verwey transition at TV = 308 K, t2g double exchange-type conduction within antiferromagnetic FeO2--BaO--FeO2 double layers proceeds by an electron hopping process that requires a spin flip of the five-fold coordinated Fe ions, costing an energy 5<J>S^2 of approximately 0.1 eV. The hopping process disrupts near-neighbor spin correlations, leading to massive damping of zone-boundary spin waves.