Evidence of electron-phonon and spin-phonon couplings at the Verwey transition inFe3O4

Abstract

Using low temperature Raman spectra on two-dimensional epitaxial ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ thin films, the presence of electron-phonon (e-p) and spin-phonon (s-p) couplings is established in the vicinity of Verwey transition (${T}_{\mathrm{V}}$). The e-p coupling is linked to ${A}_{1g}$ and ${T}_{2g}$ Raman modes and s-p to the ${T}_{2g}$ mode, below isotropic point (${T}_{\mathrm{K}}$). The parabolic dependence of the characteristic spin-correlation eigenstates on the magnetization, ${\ensuremath{\Delta}\ensuremath{\omega}}_{s\ensuremath{-}\mathrm{phn}}\ensuremath{\propto}\ensuremath{\langle}{S}_{i}|{S}_{J}\ensuremath{\rangle}\ensuremath{\propto}{[\frac{M(T)}{{M}_{S}}]}^{2}$ observed between ${T}_{\mathrm{K}}$ and ${T}_{\mathrm{V}}$ demonstrates the presence of s-p coupling. This work provides experimental evidence of the onset of correlation between these couplings and charge-orbital ordering below ${T}_{\mathrm{K}}$ to govern the Verwey transition in ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ films.