Magnetocaloric effect in composite structures based on ferromagnetic–ferroelectric Pr 0.6Sr 0.4MnO 3/BaTiO 3 perovskites

Abstract

We have prepared composite materials composed of ferromagnetic and ferroelectric compounds having the general formula (1 − x)(Pr 0.6Sr 0.4MnO 3)/ x(BaTiO 3), with x is the molar ratio ( x = 0.0, 0.03, 0.05, 0.10 and 0.30) using conventional ceramic double sintering process. We report the structural, magnetic and magnetocaloric properties of all samples. The presence of the two phases of Pr 0.6Sr 0.4MnO 3 (PSMO) and BaTiO 3 (BTO) was confirmed by X-ray diffraction (XRD) technique and the structural analysis. Magnetic measurements of magnetization versus temperature and magnetic applied field were performed. The temperature dependence of magnetization reveals that the composite samples show paramagnetic to ferromagnetic phase transition (PM–FM) when the temperature decreases. These samples have the same Curie temperature as the parent PSMO compound ( T c ≈ 273 K). The magnetic entropy change |Δ S M | was deduced from the M( H) data by the Maxwell relation. Close to T c , a large change in magnetic entropy has been observed in all samples. The maximum value of the magnetic entropy | Δ S M max | decreases from 2.88 J kg −1 K −1 for x = 0–1.86 J kg −1 K −1 for x = 0.3 for an applied magnetic field of 2 T. At this value of magnetic field the relative cooling power (RCP) decreases equally from 63 J kg −1 for the parent sample to 38.3 J kg −1 for x = 0.3. The temperature dependence of the Landau coefficients has been deduced using the Landau expansion of the magnetic free energy, indicating the second order nature of the magnetic transition.