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 (TC) and the magnetic entropy change (ΔSm) 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 (β, γ, and δ) and TC 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.