Structural, magnetic and magnetocaloric properties in La0.7-xDyxSr0.3MnO3 manganites (x = 0.00, 0.01 and 0.03)

Abstract

Structural, magnetic and magnetocaloric properties of La0.7-xDyxSr0.3MnO3 (x = 0.00, 0.01 and 0.03) powder samples have been investigated by X-ray diffraction (XRD) and magnetic measurements. Our samples have been synthesized using the sol-gel method. Rietveld refinements of the X-ray diffraction patterns show that all our samples are single phase and we have noticed that the Dy doping causes a structural transition from a rhombohedral structure with R-3c space group to an orthorhombic one with Pnma space group and a decrease in the unit cell volume. In fact, the substitution of La3+ by Dy3 induces a distortion of the unit cell, an elongation along the a- and c-axes and therefore a decrease of the unit cell volume. Magnetization measurements versus temperature in a magnetic applied field of 0.05 T show that all our samples exhibit a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature TC is found to be 319 K, 315 K and 264 K for x = 0.00, 0.01 and 0.03, respectively. Arrott plots show that all our samples exhibit a second order magnetic phase transition. From the measured magnetization data of La0.7-xDyxSr0.3MnO3 (x = 0.00, 0.01 and 0.03) samples as a function of the magnetic applied field, the associated magnetic entropy change |−ΔSM| and the relative cooling power RCP have been determined. In the vicinity of TC, |−ΔSM| reached, in a magnetic applied field of 5 T, a maximum value of 1.63 J/KgK, 1.21 J/kg K and 1.05 J/kg K for x = 0.00, 0.01 and 0.03, respectively.