The effect of Ti substitution on the magnetocaloric effect of the La0.70Sr0.30MnO3 perovskite was investigated. The magnetic entropy change (− ΔSM) was deduced by two methods: a Maxwell relation and the Landau theory. The magnetocaloric data displays a large value of the magnetic entropy change (− ΔSM) near the Curie temperature (TC = 210 K), which increases when increasing the applied magnetic field. A good agreement is found between the experimental (− ΔSM) and the one estimated by Landau theory. The relative cooling power values vary from 49 to 288 J kg− 1 upon variation of the applied magnetic field at 1 and 5 T. Under 5 T, the relative cooling power value for La0.70Sr0.30Mn0.90Ti0.10O3 is about 70% of the conventional refrigerant Gd material. As a result, the herein reported compound can be considered as a promising material in magnetic refrigeration technology.
Keywords: Perovskites; Magnetic refrigerant; Magnetocaloric effect; Magnetic entropy; Landau theory
Fig. 1. Isothermal magnetization for La0.7Sr0.3Mn0.9Ti0.1O3 sample measured at different temperatures. Inset a is the plot of magnetization vs. temperature under 0.01 and 1 T applied magnetic fields (μ0H) and inset b indicates the dM/dT curve used to determine TC.
Fig. 2. μ0H/M vs. M2 curves of isotherms for La0.7Sr0.3Mn0.9Ti0.1O3 sample. Insets a and b indicate the temperature dependence of the coefficients A and B respectively.
Fig. 3. Magnetic entropy change (− ΔSM) of La0.7Sr0.3Mn0.9Ti0.1O3 as a function of temperature upon different magnetic fields (μ0H). Inset a represents the maximum entropy change (|ΔSMmax|) and the RCP values vs. applied magnetic field (μ0H) for undoped and Ti-modified materials. Inset b shows the experimental and theoretical magnetic entropy change (− ΔSM) upon μ0H = 1 and 2 T for the La0.7Sr0.3Mn0.9Ti0.1O3 sample.
Comparison of reported values of the maximum magnetic entropy change (|ΔSMmax|) and RCP values at the Curie temperature (TC) under a magnetic field (μ0H), for various perovskite manganites and the two Gd and Gd5Ge2Si2 magnetic refrigerant materials.