Magnetic, magnetocaloric and critical behavior investigation of La0.7Ca0.1Pb0.2Mn1−x−yAlxSnyO3 (x, y = 0.0, 0.05 and 0.075) prepared by a sol–gel method

Abstract

A systematic study on the magnetic, magnetocaloric and critical behavior properties of polycrystalline La_0.7Ca_0.1Pb_0.2Mn_1−x−yAl_xSn_yO₃ prepared via a sol–gel method are studied. These compounds present a single magnetic transition from a ferromagnetic (FM) to paramagnetic (PM) phase with decreasing temperature. The critical exponents are estimated using various techniques, such as a modified Arrott plot, the Kouvel–Fisher method and critical isotherm analysis based on the data of static magnetic measurements recorded around the Curie temperature, T_C. The estimated critical exponent values are found to be consistent and comparable to those predicted by the 3D-Ising model for x, y = 0.0 and by the mean field model for x, y = 0.05 and 0.075. We have confirmed the obtained critical exponents with the single scaling equation: M(μ₀H,ε) = ε^βf ± (μ₀H/ε^β+γ), where ε = (T − T_C)/T_C is the reduced temperature. We have investigated the validity and usefulness of theoretical modeling in our compound La_0.7Ca_0.1Pb_0.2Mn_1−x−yAl_xSn_yO₃ based on the mean-field analysis of the magnetic entropy change (−ΔS_M) versus the magnetization data. For comparison, the M_Sp has been also deduced from the classical extrapolation of the Arrott plot. We obtain an excellent agreement between the spontaneous magnetization determined from the entropy change (−ΔS_M vs. M²) and the Arrot curves (μ₀H/M vs. M²), confirming the validity of the magnetic entropy change approach in order to estimate the spontaneous magnetization M_Sp in a ferromagnetic system.