Above Room Temperature Magnetocaloric Effect In Perovskite Pr_(0.6)sr_(0.4)mno_3

摘要

The dependence of magnetization M on the applied magnetic field H and temperature T was measured carefully, near the Curie temperature T_c for the perovskite manganite sample Pr_(0.6)Sr_(0.4)MnO_3. The experimental results indicate that this specimen exhibit ferromagnetic (FM) to paramagnetic (PM) transition at T_c～320 K. In the 200 K-45 K temperature range the spontaneous magnetization was decreasing, probably due to spin canted state between manganese and praseodymium spin systems. At 46 K the magnetization presents a second little transition, which can be ascribed to very weak traces of secondary Mn_3O_4 phase, and remains constant between 10 K and 46 K. The maximum value of the magnetic entropy change obtained from the M(H) plot data is |ΔS_M~(max)| = 2.3 Jkg~(-1) K~(-1) for applied magnetic field of 2.5 T. At this value of magnetic field the relative cooling power (RCP) is 34.5 Jkg~(-1). The temperature corresponding to ΔS_M maximum value is almost equal to T_c. The large entropy change can be attributed to the fact that the ferromagnetic transition enhances the effect of the applied magnetic field greatly. It is suggested by the results that this compound can be used as the working material in an active magnetic regenerative refrigerator above room temperature.