Structural transformation in magnetite below the Verwey transition

摘要: The magnetite structure was studied with synchrotron x-ray powder diffraction above and below the Verwey transition. A symmetry-mode analysis performed to obtain atomic displacements from amplitudes of condensing modes. main contributing modes that drive structural phase transition at temperature correspond irreducible representations ${\ensuremath{\Delta}}_{5}$, ${X}_{1}$, ${X}_{4}$, ${W}_{1}$, ${W}_{2}$. $W$ modes, neglected so far, must be taken into account a reliable description low-temperature crystal can obtained. This is refined in nonpolar space group $C$2/$c$ ten nonequivalent octahedral irons. condensation mentioned leads wide distribution local environments around iron atoms, whose valences range between 2.53 2.84. finding rules out any bimodal charge disproportionation i.e., an ${\mathrm{Fe}}^{2+}$-like/${\mathrm{Fe}}^{3+}$-like ordering.