Room temperature magnetocaloric effect, critical behavior, and magnetoresistance in Na-deficient manganite La0.8Na0.1MnO3

The La0.8Na0.1MnO3 oxide was prepared by the solid-state reaction and annealed in air. The X-ray diffraction data reveal that the sample is crystallized in a rhombohedral structure with R (3) over barc space group. Magnetic study shows a second-order magnetic phase transition from ferromagnetic to paramagnetic state at the Curie temperature T-C = 295 K. In addition, the magnetizations as a function of temperature and the magnetic field is used to evaluate the magnetic entropy change Delta S-M. Then, we have deduced that the La0.8Na0.1MnO3 oxide has a large magnetocaloric effect at room temperature. Such effect is given by the maximum of the magnetic entropy change Delta S-Mmax = 5.56, and by the Relative cooling power (RCP) factor which is equal to 235 under a magnetic field of 5 T. Moreover, the magnetic field dependence of the magnetic entropy change is used to determine the critical exponents beta,gamma, and delta which are found to be beta = 0.495, gamma = 1.083, and delta = 3.18. These values are consistent with the prediction of the mean field theory (beta = 0.5, gamma = 1, and delta = 3). Above all, the temperature dependence of electrical resistivity shows a metal-insulator transition at T-rho. The electrical resistivity decrease when we apply a magnetic field giving a magnetoresistance effect in the order of 60% at room temperature. (C) 2014 AIP Publishing LLC.