The colossal magnetoresistance within wide temperature range in LaMnO₃ compound

The microstructure and magnetotransport of LaMnO₃ manganite have been studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) at room temperature show that the LaMnO₃ sample has a single-phase orthorhombic structure, and the sample particles and elements are densely and evenly distributed. By studying the temperature dependence of resistivity and magnetoresistance (MR), and the magnetic filed dependence of resistivity, it is found that the resistivity versus temperature curves of LaMnO₃ show three extreme values in the temperature range of 10–390 K. Firstly, the minimum resistivity at about 70 K comes from the spin polarization tunneling effect. Secondly, there is a maximum resistivity near 189 K due to the inhomogeneity of the polycrystalline sample. Finally, the traditional metal to insulator (MI) transition leads to another maximum resistivity near 241 K, where the corresponding temperature is MI transition temperature (T_MI). Moreover, the resistivity of LaMnO₃ exhibits a decline as the external magnetic field being increased, implying the presence of MR. In the region of low temperature (close to the T_MI), the negative MR reaches 14.68 and 45.28% under 1 T and 4 T applied fields, respectively. The coexistence of two kinds of MR mechanisms in LaMnO₃ induced by spin polarization tunneling and Jahn–Teller distortion leads to the enhanced MR within the wide temperature range (10–265 K).