Spin resolved electron density study of YTiO(3) in its ferromagnetic phase: signature of orbital ordering

The present work reports on the charge and spin density modelling of YTiO(3) in its ferromagnetic state (T (C) = 27 K). Accurate polarized neutron diffraction and high-resolution X-ray diffraction (XRD) experiments were carried out on a single crystal at the ORPHÉE reactor (LLB) and SPRING8 synchrotron source. The experimental data are modelled by the spin resolved pseudo-atomic multipolar model (Deutsch et al., 2012 ▸). The refinement strategy is discussed and the result of this electron density modelling is compared with that from XRD measured at 100 K and with density functional theory calculations. The results show that the spin and charge densities around the Ti atom have lobes directed away from the O atoms, confirming the filling of the t (2g) orbitals of the Ti atom. The d (xy) orbital is less populated than d (xz) and d (yz), which is a sign of a partial lift of degeneracy of the t (2g) orbitals. This study confirms the orbital ordering at low temperature (20 K), which is already present in the paramagnetic state above the ferromagnetic transition (100 K).