Magnetocaloric effect and critical behavior near the first to second-order phase transition of La0.7Ca0.3-xSnxMnO3 compounds

Abstract

The magnetocaloric effect and the critical behavior near the first to second-order phase transition of La0.7Ca0.3-xSnxMnO3 compounds (with x = 0-0.04), which were prepared by a conventional solid state reaction method, have been investigated. With increasing Sn-doping, a systematic decrease in the Curie temperature (T-C) and the magnetic entropy change (Delta S-m) are observed. We also pointed out that the width and the order of the magnetic phase transition in La0.7Ca0.3-xSnxMnO3 compounds can be easily modified by changing Sn concentration. The Banerjee criterion suggests that the Sn-undoped sample (x = 0) undergoes a first-order phase transition (FOPT). Meanwhile, Sn-doped samples (x = 0.02 and 0.04) undergo a second-order phase transition (SOPT). Based on the Kouvel-Fisher method and the critical isotherm analyses, we have determined the values of the critical exponents (beta, gamma, and delta) and T-C for two SOPT samples. The results obtained for x = 0.02 sample are beta = 0.218, gamma = 0.858, and delta = 4.717, which are close to those expected for the tricritical mean field theory. Whereas, beta = 0.468, gamma = 1.095 and delta = 3.315 obtained for x = 0.04 sample are close to those expected for the mean field theory. This suggests that the presence of Sn favors establishing the ferromagnetic long-range interactions in the sample.