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

The magnetocaloric effect and the critical behavior near the first to second-order phase transition of La 0.7 Ca 0.3-x Sn x MnO 3 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 (Δ S m ) are observed. We also pointed out that the width and the order of the magnetic phase transition in La 0.7 Ca 0.3-x Sn x MnO 3 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 ( β , γ , and δ ) and T C for two SOPT samples. The results obtained for x  = 0.02 sample are β  = 0.218, γ  = 0.858, and δ  = 4.717, which are close to those expected for the tricritical mean field theory. Whereas, β  = 0.468, γ  = 1.095 and δ  = 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.