Abstract
A systematic study on the magnetic, magnetocaloric and critical behavior properties of polycrystalline La0.7Ca0.1Pb0.2Mn1-x-yAlxSnyO3 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(mu H-0, epsilon) = 3 epsilon(beta)f +/- (mu H-0/epsilon(beta+gamma)), where epsilon = (T - T-C)/T-C is the reduced temperature. We have investigated the validity and usefulness of theoretical modeling in our compound La0.7Ca0.1Pb0.2Mn1-x-yAlxSnyO3 based on the mean-field analysis of the magnetic entropy change (Delta S-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 (-Delta S-M vs. M-2) and the Arrot curves (mu H-0/M vs. M-2), confirming the validity of the magnetic entropy change approach in order to estimate the spontaneous magnetization MSp in a ferromagnetic system.