Spin and orbital ordering in Y _1-xLa _xVO ₃

The spin and orbital ordering in Y _1-xLa _xVO ₃ (0.30 ≤ x ≤ 1.0) has been studied to map out the phase diagram over the whole doping range 0 ≤ x ≤ 1. The phase diagram is compared with that for RVO 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 ≤ T _N as in LaVO ₃. The magnetic ordering below T _t ≤ T _N is G type in the compositional range 0.20 ≤ x ≤ 0.40 and C type in the range 0.738 ≤ x ≤ 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 ≤ 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/χ(T). We argue that T ^* represents a temperature below which spin and orbital fluctuations couple together via λL•S.