Different effects of Ce-doping on orbital and spin ordering in perovskite vanadate Sm_1-xCe_xVO₃

The effects of Ce-doping on the phase transition of the orbital/spin ordering (OO/SO) are studied through the structural, magnetic, and electrical transport measurements of perovskite vanadate Sm_1-xCe_xVO₃. The measurements of structure show that the cell volume decreases as x ≤ 0.05, and then increases as Ce-doping level increases further. The OO state exists but is suppressed progressively in the sample with x ≤ 0.2 and disappears as x>0.2. The temperature at which the C-type SO transition is present increases monotonically with Ce-doping level increasing. The temperature dependence of resistivity for each of all samples shows a semiconducting transport behavior and the transport can be well described by the thermal activation model. The activation energy first decreases as x ≤ 0.2, and then increases for further doping. The obtained results are discussed in terms of the mixed-valent state of the doped-Ce ions.