Influence of Crystallite Size on Magnetocaloric Effect and Critical Behavior La<sub>0.7</sub>Sr<sub>0.3</sub>Mn<sub>0.92</sub>Co<sub>0.08</sub>O<sub>3</sub> Nanoparticles

Abstract

Four samples of La0.7Sr0.3Mn0.92Co0.08O3 (LSMCO) with different crystallite sizes were prepared by the combination of solid-state reaction and mechanical milling methods. Based on isothermal magnetization data, ${M}$ ( $\boldsymbol {H}$ ), temperature dependences of magnetic entropy change, $\Delta \boldsymbol {S} _{m} {T}$ , of the samples under a magnetic field change of 10 kOe were calculated. The maximum values of magnetic entropy change (| $\Delta {S} _{\mathrm {max}}$ |) at room temperature are in the range of 0.9–1.4 J $\cdot $ $\mathrm{kg}^{{\mathbf {-1}}}\cdot $ $\mathrm{K}^{{\mathbf {-1}}}$ , corresponding to ferromagnetic (FM)–paramagnetic phase transition. In addition, ${M} ^{{\mathbf {2}}}$ versus ${H}/{M}$ curves at temperatures around ${T} _{C}$ prove the samples exhibiting a second-order magnetic phase transition. The critical exponents $\beta $ , $\gamma $ , and $\delta $ were determined using the modified Arrott plot method and critical isotherm analysis. Here, these exponent values are located in between those expected for the mean-field theory and 3-D Heisenberg model. It means the coexistence of short-range and long-range FM interactions in LSMCO nanoparticles.