Soft resonant x-ray scattering in highly stoichiometric magnetite

We report here soft resonant x-ray scattering (SRXS) measurements on a single crystal of highly stoichiometric Fe₃O₄ (Verwey transition at T_v = 123.5 K). Resonant intensity was observed at the Fe L_2,3 and the O K edges for the (0,0,1/2) reflection and at the Fe L₁-edge for the (001) reflection in the low temperature phase. The energy, azimuthal angle and temperature dependence was explored using either σ- or π-incidence. The (001) reflection is active in the σ-σ' polarization channel whereas the (0,0,1/2) reflection is in the σ-π' polarization one. The (0,0,1) reflection is also observed at energies below the Fe L₁-edge, confirming that this reflection is permitted by the crystal symmetry of the low temperature phase. On the other hand, the (0,0,1/2) reflection is strictly forbidden and scattered intensity is only observed on resonance. The resonant and non-resonant signals simultaneously disappear at T_V for the two studied reflections at both the Fe L-edges and the O K-edge. This result indicates that the resonant reflections and the associated electronic anisotropy of the Fe d, Fe p and O p-states are explained by the lattice distortions.