Critical competition between two distinct orbital-spin ordered states in perovskite vanadates

Abstract

We have investigated the spin/orbital phase diagram in the perovskite orthovanadate $R{\text{VO}}_{3}$ ($R=\text{Eu}$, Y, Dy, and Ho) by measurements of magnetization, dielectric constant, specific heat, Raman scattering spectra, and x-ray diffraction, focusing on the interplay between the $\text{V}\text{ }3d$ spin and the $4f$ moment of the $R$ ion. The thermally induced phase transition between the C-type spin/G-type orbital ordered state and the G-type spin/C-type orbital ordered state is observed for ${\text{Eu}}_{1\ensuremath{-}x}{\text{Y}}_{x}{\text{VO}}_{3}$ $(x=0--0.52)$ without $4f$ moment. By comparing this phase diagram with the spin/orbital ordering in ${\text{TbVO}}_{3}$, it is evident that the critical competition between the C-type spin/G-type orbital ordered phase and the G-type spin/C-type orbital ordered one depends not only on the ${\text{GdFeO}}_{3}$-type lattice distortion but also on the presence of the $4f$ moment of the $R$ ion. The magnetic field induced phase transition of the spin/orbital ordering is achieved concomitantly with polarizing $R\text{ }4f$ moments for ${\text{DyVO}}_{3}$ and ${\text{HoVO}}_{3}$. For ${\text{DyVO}}_{3}$, the G-type spin/C-type orbital ordered phase is switched to the C-type spin/G-type orbital ordered one by applying a moderate magnetic field around 3 T. By contrast, the G-type spin/C-type orbital ordering is rather favored under the magnetic field in ${\text{HoVO}}_{3}$. The results cannot be uniquely explained in terms of the exchange interaction between the $\text{V}\text{ }3d$ spin and the $R$-ion $4f$ moment. The coupling of the $R\text{ }4f$ moment polarization with the lattice distortion tied with the orbital ordering of the $\text{V}\text{ }3d$ sublattice may also be relevant to this field induced phase transition.