Modeling of magnetic and magnetocaloric properties of polycrystalline La0.85Sr0.15Mn0.99Fe0.01O3 by a mean-field scaling method

Abstract

Magnetic and magnetocaloric properties of La0.85Sr0.15Mn0.99Fe0.01O3 perovskite oxides are investigated in the framework of the mean-field theory with a goal to develop a comprehensive model with parameters that can be used to optimize the caloric performances for cooling applications. Using the experimental magnetic isotherms M(H,T), we estimate and compare the exchange parameter (λ), the saturation magnetization (M0), the total angular momentum (J), and the gyromagnetic factor (g) for two different samples annealed at 1170 and 1250 °C. These parameters are used, in turn, in the simulation of the magnetic and the magnetocaloric properties of these La0.85Sr0.15Mn0.99Fe0.01O3 compounds assuming imperfect samples with compositional and/or magnetic inhomogeneities. For this purpose, a Gaussian distribution of the Curie temperature is assumed. The temperature dependence of the magnetic entropy change, −ΔSM(T), resulting from an applied field variation is simulated for both samples. The selected distribution captures the rounding of the −ΔSM(T) peak at its maximum and its broadening with growth conditions, features that are constantly observed in many bulk polycrystalline compounds.