Structural, magnetic and magnetocaloric properties of polycrystalline La0.65Ca0.35Mn0.95Ni0.05O3

Highlights: • The traditional sol-gel method was improved by using citric acid as complexant, shortening the preparation period and reducing the sintering temperature. • Doping at the Mn site severely affects the Curie temperature of the sample. Our results show the sample La_0.65Ca_0.35Mn_0.95Ni_0.05O₃ exhibited a magnetic entropy change -ΔS_M 4.76 J/kg K and a RCP 69.59 J/kg under a 3.0 T magnetic field near Tc. • In theory, the parameters such as magnetic entropy change and relative refrigeration capacity of the prepared products are simulated, and the experimental results are compared with the theoretical predictions. • The sample we obtained can be used as candidates for potential applications for magnetic refrigeration. -- Abstract: Polycrystalline perovskite-type manganite La_0.65Ca_0.35Mn_1-xNi_xO₃ were prepared by sol-gel method. X-ray diffraction measurement showed that all samples have a single phase. Rietveld's refinement result of X-ray diffraction indicates that our samples have an orthorhombic structure with pnma space group. Magnetization measurements versus temperature in a magnetic applied field of 0.1 T showed that Ni-doping leads to a paramagnetic to ferromagnetic transition with a Curie temperature decreasing from 272 K to 194 K. When x = 0.05, the Tc of the sample was adjusted to near room temperature. The maximum magnetic entropy change -ΔS_M corresponding to a 3 T magnetic field variation was found to be 4.76 J/kg K and about 69.59 J/kg of relative cooling power for La_0.65Ca_0.35Mn_0.95Ni_0.05O₃. Besides, Arrott plots showed that our sample exhibit a second-order on the phase transition of the manganite.