Structural, magnetic and magnetocaloric investigation of La_(0.67)Ba_(0.33)IVln_(1-x)Ni_xO_3 (x = 0,0.025 and 0.075) manganite

摘要

In this paper, we report the structural, magnetic and magnetocaloric properties of Ni-doped La0.67Ba0.33Mn1-xNixO3 (x = 0, 0.025 and 0.075) manganites. Our compounds were synthesized using the sol-gel method. The structural analysis using Rietveld refinement shows that Ni-doped LaBaMnO3 system crystallizes in the rhombohedral symmetry with space group. Magnetization measurements versus temperature in a magnetic applied field of 0.05 T reveal that all the compositions exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. A systematic decrease in the transition temperature is clearly observed upon Ni doping and a near room temperature T-C (302 K) is achieved with x = 0.075 composition. The maximum magnetic entropy change in a magnetic field change of 5 T is found to be 2.12, 2.78 and 1.78 J/kg K for x = 0, 0.025 and 0.075, respectively. At this value of magnetic field, large relative cooling power values are obtained in our samples, especially for x = 0.075 (271 J/kg) making it a promising candidate for magnetic refrigeration near room temperature.