Spin and orbital ordering in Y1−xLaxVO3

The spin and orbital ordering in Y${}_{1\ensuremath{-}x}$La${}_{x}$VO${}_{3}$ (0.30 \ensuremath{\leqslant} $x$ \ensuremath{\leqslant} 1.0) has been studied to map out the phase diagram over the whole doping range 0 \ensuremath{\leqslant} $x$ \ensuremath{\leqslant} 1. The phase diagram is compared with that for $R$VO${}_{3}$ ($R$ = rare earth or Y) perovskites without $A$-site variance. For $x$ > 0.20, no long-range orbital ordering was observed above the magnetic ordering temperature ${T}_{N}$; the magnetic order is accompanied by a lattice anomaly at a ${T}_{t}$ \ensuremath{\leqslant} ${T}_{N}$ as in LaVO${}_{3}$. The magnetic ordering below ${T}_{t}$ \ensuremath{\leqslant} ${T}_{N}$ is $G$ type in the compositional range 0.20 \ensuremath{\leqslant} $x$ \ensuremath{\leqslant} 0.40 and $C$ type in the range 0.738 \ensuremath{\leqslant} $x$ \ensuremath{\leqslant} 1.0. Magnetization and neutron powder diffraction measurements point to the coexistence below ${T}_{N}$ of the two magnetic phases in the compositional range 0.4 $x$ 0.738. Samples in the compositional range 0.20 $x$ \ensuremath{\leqslant} 1.0 are characterized by an additional suppression of a glasslike thermal conductivity in the temperature interval ${T}_{N}$ $T$ ${T}^{*}$ and a change in the slope of 1/\ensuremath{\chi}($T$). We argue that ${T}^{*}$ represents a temperature below which spin and orbital fluctuations couple together via $\ensuremath{\lambda}\mathbf{L}\ifmmode\bullet\else\textbullet\fi{}\mathbf{S}$.