The magnetocaloric effect is calculated for La_1-xCe_xMnO₃ system near a phase transition from ferromagnetic to paramagnetic state as a function of temperature. It is suggested by the results that La_1-xCe_xMnO₃ material can be utilized as the working material in an active magnetic regenerative refrigerator with large temperature span, for its significant entropy change upon the application of a magnetic field and the easily tuned Curie temperature.

The electrocaloric (EC) effect accompanied with the ferroelectric to paraelectric phase transition in (111)-oriented PbMg_1/3Nb_2/3O₃ (PMN) is investigated. It is shown that the largest change $\Delta T$ is 0.37 K in 3 kV/cm electric field shift near the Curie temperature of 221 K; that is, the cooling $\Delta T$ per unit field (MV/m) is 1.23×10^-6 m·K/V. This value is significantly larger, and comparable with the value of 0.254×10^-6 m·K/V for PbZr_0.95Ti_0.05O₃ thin film under larger electric field shift $\Delta E$ = 30 kV/cm. Thus, the EC effect of (111) PMN single crystal provides cooling solutions at low temperatures, and opens more opportunities for practical application in cooling systems.

The magnetocaloric effect (MCE) achieved for La_0.7Sr_0.3MnO₃/Ta₂O₅ composites has been investigated. The maximum value of magnetic entropy change of La_0.7Sr_0.3MnO₃ composites is found to decrease slightly with the further increasing of Ta₂O₅ concentration. It is shown that La_0.7Sr_0.3MnO₃/Ta₂O₅ composites exhibit much more uniform magnetic entropy change than that of gadolinium. Moreover, the results indicate that the temperature range between 100 K and 400 K can be covered using the La_0.7Sr_0.3MnO₃/Ta₂O₅ composites. Therefore, MCE makes the composites promising for room-temperature magnetic cooling applications.

In this work, a phenomenological model is applied to describe the magnetocaloric effect for the La_0.75Ca_0.25MnO₃ system near a second-order phase transition from a ferromagnetic to a paramagnetic state. Based on this model, it can predict the values of the magnetocaloric properties from calculation of magnetization as a function of temperature under different external magnetic fields. The magnetic entropy change reaches a peak of about 5.39 J/(kg·K) at 257 K upon 4 T applied field variation. The ∆S_M distribution is much more uniform than that of gadolinium, which is desirable for an Ericson-cycle magnetic refrigerator.