Influence of Sr substitution on structural, magnetic and magnetocaloric properties in La_0.67Ca_0.33−xSr_xMn_0.98Ni_0.02O₃ manganites

A systematic investigation of the effect of Strontium (Sr) doping on the structure, magnetic behavior, and magnetocaloric properties of the manganite perovskites \({\text{La}}_{{0.67}} {\text{Ca}}_{{0.33 - x}} {\text{Sr}}_{x} {\text{Mn}}_{{0.98}} {\text{Ni}}_{{0.02}} {\text{O}}_{3}\) (LCSMNO) has been performed. The Sr content x takes three values, namely 0.15, 0.2, and 0.3. The sol–gel technique has been employed in the preparation of our compounds. The structural analysis has revealed that our samples exhibit a rhombohedral structure with \(R\bar{3}c\) space group symmetry, close to ambient temperature. A second-order paramagnetic (PM) to ferromagnetic (FM) transition has been validated over the Curie temperature range T_C between 319 K (x = 0.15) to 353 K (x = 0.3), based on Arrott's analysis with the behavior of the master curve. According to the calculations made, the maximal values of the magnetic entropy change \({(-\Delta S}_{M}^{max})\) resulting through Landau's theory and the ones obtained by the classic Maxwell relationship are very close. We find the value of \({(-\Delta S}_{M}^{max})\) is equal to 4.386, 4.469, and 4.250 J Kg⁻¹ K⁻¹, respectively, for x = 0.15, 0.2, and 0.3, when an external magnetic field μ0H = 5 T is applied. Based on the results of the study in this work, we find that controlled Sr doping adapts perfectly to the magnetic as well as the magnetocaloric properties of the LCMNO, which plays an important role in the implementation of many potential applications of the material in the field of near-ambient temperature magnetic refrigeration technology.