Structural, magnetic and magnetotransport properties of La_0.7−xCe_xBa_0.3MnO₃ (x = 0–0.4) have been investigated although some unreacted secondary phases of CeO₂ were present. The rhombohedral structure (R-3c) forx = 0 transforms to orthorhombic with the space groupImma forx = 0.3. All samples showed ferromagnetic transition above 300 K and a negative magnetoresistance. For x>0.1, magnetization data measured at 1 T showed a decrease at low temperatures (T < 50 K) due to antiferro-magnetic coupling between Ce-local moments and Mn-moments. Forx = 0.4, the resistivity showed a maximum around 200 K which corresponds to ordering temperature of cerium. Since these results are similar to that observed in the Sr-containing La_0.5−xCe_xSr_0.5MnO₃ (x = 0–0.4) system, we suggest that the cerium ions are in the trivalent state and the anomalous behaviour has been attributed to a Kondo-like effect.

We have investigated the magnetocaloric effect across a first order structural transition coupled to the ferromagnetic transition ($T_C \sim 270$ K) in Pr_0.1Ce_0.4Sr_0.5MnO₃ using magnetization and heat capacity measurements. The adiabatic magnetic entropy change |$\Delta S$| obtained from magnetization measurements for a magnetic field change of 2 T is around 1.3 J/kg K. A similar value of |$\Delta S$| was obtained from the analysis of heat capacity data.