Magnetocaloric Effect Near Room Temperature of La0.67Ca0.33-x Sr x MnO3 (x=0.06, 0.07, 0.08) Manganites

Structural and magnetic properties of La-0.67 Ca0.33-x Sr (x) MnO3 (x = 0.06, 0.07, 0.08) manganites synthesized using the solid-state reaction method were investigated. Rietveld refinement of the X-ray diffraction patterns shows that all our samples crystallize in the orthorhombic structure with Pbnm space group. The temperature dependence of magnetization reveals that all the samples exhibit a ferromagnetic (FM) to paramagnetic (PM) transition at temperatures of 279 K for La-0.67 Ca0.27Sr0.06MnO3, 286 K for La0.67Ca0.26Sr0.07MnO3, and 293 K for La0.67Ca0.25 Sr0.08MnO3. Using Arrot plots, the phase transition from FM to PM is found to be of second order. The maximum of themagnetic entropy change (-Delta S (M)) is found to be 3.37, 2.74, and 2.60 J kg(-1) K-1 for x = 0.06, 0.07, and 0.08 under a magnetic field change of 3 T. The relative cooling power (RCP-1) for La0.67Ca0.33-x Sr (x) MnO3 sample is 152, 162, and 164 J kg(-1) for x = 0.06, 0.07, and 0.08. According to these results, these kinds of samples are promising materials for magnetic refrigerants in the room-temperature region.