Influence of Crystallite Size on Magnetocaloric Effect and Critical Behavior La_0.7Sr_0.3Mn_0.92Co_0.08O₃ Nanoparticles

摘要

Four samples of LaSrMnCoO (LSMCO) with different crystallite sizes were prepared by the combination of solid-state reaction and mechanical milling methods. Based on isothermal magnetization data, (), temperature dependences of magnetic entropy change, , of the samples under a magnetic field change of 10 kOe were calculated. The maximum values of magnetic entropy change (||) at room temperature are in the range of 0.9–1.4 J, corresponding to ferromagnetic (FM)–paramagnetic phase transition. In addition, versus curves at temperatures around prove the samples exhibiting a second-order magnetic phase transition. The critical exponents , , and were determined using the modified Arrott plot method and critical isotherm analysis. Her- , 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.