Structural, magnetic and magnetocaloric properties of Co-doped nanocrystalline La0.7Te0.3Mn0.7Co0.3O3

Abstract

Structural, magnetic and magnetocaloric properties of the nanocrystalline La0.7Te0.3Mn0.7Co0.3O3 perovskite manganite were investigated. X-ray diffraction pattern indicated that the nanocrystalline sample crystallized in orthorhombic crystal structure with Pbnm space group. The average particle size was calculated using scanning electron microscope and it was found to be ∼150nm. Temperature dependence magnetization measurements revealed ferromagnetic–paramagnetic phase transition and the Curie temperature (TC) was found to be ∼201K. Field dependence magnetization showed the hysteresis at low temperature with a coercive field of ∼0.34T and linear dependence at high temperature corresponds to paramagnetic region. Based on the magnetic field dependence magnetization data, the maximum entropy change and relative cooling power (RCP) were estimated and the values were 1.002Jkg−1K−1 and 90Jkg−1 for a field change of 5T respectively. Temperature dependent resistivity ρ(T) data exhibited semiconducting-like behavior at high temperature and the electrical transport was well explained by Mott’s variable-range hopping (VRH) conduction mechanism in the temperature range of 250K–300K. Using the VRH fit, the calculated hoping distance (Rh) at 300K was 54.4Å and density of states N(EF) at room temperature was 7.04×1018eV−1cm−3. These values were comparable to other semiconducting oxides.