We have systematically investigated the compositional dependence of the magnetic and magnetocaloric properties of La0.7-xPrxSr0.3MnO3 (LPSMO). Polycrystalline samples of LPSMO with 0.02 ≤ x ≤ 0.30 were prepared by a standard solid-state reaction method with phase purity and structure confirmed using x-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal second order ferromagnetic transitions in each sample with Curie temperature decreasing progressively with increasing Pr content from ∼350 K for x = 0.02 to ∼295 K for x = 0.30. Magnetic entropy change (ΔSM) was calculated by applying the thermodynamic Maxwell equation to a series of isothermal field dependent magnetization curves. In the sample with x = 0.30, the maximum value of −ΔSM reaches ∼2.08 J/kg K at 295 K for a field change of 1.5 T. Reduced Pr content corresponds to larger values of entropy change, reaching −ΔSM ∼2.79 J/kg K for the x = 0.02 doping. The refrigeration capacity for each composition reached sizable values of 33–48 J/kg for a small applied field of 1.5 T.

We report a systematic study of the magnetic and magnetocaloric properties of La0.7Ca0.3Mn1-xFexO3, where trivalent Fe is substituted for Mn on the perovskite B-site in the doping range 0.00≤x≤0.07. The polycrystalline materials were prepared by a standard solid state reaction method and X-ray diffraction confirmed that Fe was incorporated without significant structural changes. Magnetic measurements indicate that the ferromagnetic double exchange interaction is weakened with increasing Fe concentration, resulting in a shift in TC from 263 K to 114 K as x varied between 0.00 and 0.07. The large entropy change of 7.7 J/kg K found in the sample with x=0 for a field change of 3 T is initially enhanced to 8.6 J/kg K for x = 0.01, which is likely due to oxygen deficiency. As Fe content increased further, peak entropy values were seen to decline. However, a simultaneous broadening of the ΔSM(T) peaks led to enhanced refrigerant capacity (RC) in the Fe-doped samples of up to 30% over that of La0.7Ca0.3MnO3. Arrott plot analyses and a universal curve method were applied to study the order of the magnetic transition in this system. The incorporation of Fe led to a weakening of first-order nature of the paramagnetic to ferromagnetic transition in La0.7Ca0.3MnO3 and finally initiated a change from first to second order for x > 0.05.

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