Room temperature magnetocaloric effect and critical behavior in La0.67Ca0.23Sr0.1Mn0.98Ni0.02O3 oxide

The structural, magnetic and magnetocaloric properties of La 0.67 Ca 0.23 Sr 0.1 Mn 0.98 Ni 0.02 O 3 nano-crystalline manganite are investigated systematically. The compound is elaborated based on Pechini sol–gel method and then annealed at 1000 °C for 24 h. X-ray powder diffraction shows that, the sample crystallizes in a rhombohedral structure with R 3 ¯ C space group. A magnetization versus temperature study shows that the compound exhibits a second-order magnetic transition from a ferromagnetic to a paramagnetic state at a Curie temperature T C = 296 K. To evaluate the magnetic entropy change Δ S M , we measure the magnetization as a function of temperature and magnetic field. At ambient temperature, we find that La 0.67 Ca 0.23 Sr 0.1 Mn 0.98 Ni 0.02 O 3 sample has a very important magnetocaloric effect (MCE). In a magnetic field variation of 5 T, this MCE is explained by a maximum of magnetic entropy change Δ S M max and a big RCP values at 4.92 J . Kg - 1 K - 1 and 145 J/kg, respectively, around room temperature (296 K), which give the possibility of technologic application in magnetic refrigeration area. In addition, we find an admirable estimate of the magnetic entropy change, which is based on the Landau theory. Finally, we use the magnetic field dependence of Δ S M to determine the critical exponents of the system and we find that β = 0.39, γ = 1.35, and δ = 4.43, are very close to those predicted to the 3D-Heisenberg model. These results indicate that the present compound is one of candidate materials for magnetic refrigerators near room temperature.