Critical Behavior and Magnetocaloric Effect in La2NiMnO6 Nanocrystals

In this paper, we present a detailed study on the magnetocaloric effect (MCE) and the critical behavior of La2NiMnO6 (LNMO) nanocrystals. Cubic-structured LNMO samples with different crystallite sizes (d = 200 to 26.4 nm) were prepared by a combination of solid-state reaction and mechanical milling with milling time (t(m)) changing from 0 to 30 min. The results show that all the samples undergo the second-order phase transition. Using the modified Arrott plot and critical isotherm analysis methods, we have analyzed the critical behavior for nanocrystals to obtain the optimal values of the critical parameters (beta, gamma, delta and T-C). The results indicate that short- and long-range ferromagnetic interactions coexist in the samples. In addition, we also assess the MCE of the samples via the magnetic entropy change (Delta S-M). Based on the obtained Delta SM(T, H) data, we have also described the universal master curve for Delta SM, which as a function of Delta S-M(T)/Delta S-M(P) versus rescaled temperature theta = (T - T-C)/(T-r - T-C), where T-r is the reference temperature. Interestingly, all the Delta S-M (T, H) data points are collapsed into a universal curve in the whole temperature range.