Synthesis and magnetocaloric properties of La0.67Ca0.29Sr0.04MnO3 obtained from modified sol-gel Pechini method

This work deals with the study of the physical properties of substituted lanthanum manganite, La0.67Ca0.29Sr0.04MnO3, prepared by using a modified sol-gel Pechini method. The manganite was obtained following the traditional Pechini method, but starting from an unusual mixture of precursors wherein manganese sulfate replaces the manganese nitrate. This single change induces variations on the physical properties of the compound. The phase crystallization was analyzed using X-ray diffraction along with the Rietveld method of refinement of the structure. Morphological analysis showed particle sizes around 0.5 µm organized in porous structures and forming cubic clusters. The manganite exhibits high crystallinity and second-order ferromagnetic–paramagnetic transition near room temperature. Also, the magnetocaloric effect and the maximum entropy change (ΔSMmax) were calculated by using a phenomenological model. The associated magnetic entropy change |ΔSM| and the relative cooling power have been determined from the phenomenological parameters as a function of the applied magnetic field. In the vicinity of the Curie temperature (TC), ΔSM reached a maximum value of 2.44 J/kgK when 3 T of magnetic strength was applied.