Field dependence of magnetoresistance in half-metallic manganite

Formular description of the magnetic field dependence of resistivity is of interest not only because of its theoretical importance, but also because it allows us to design magnetic-field-controlled devices. Using micromagnetic theory combined with charge carrier hopping and spin-polarized tunneling models, the magnetic field dependence of resistivity in half-metallic ferromagnet La 2/3 Sr 1/3 MnO 3 has been studied systematically. It has been shown that the resistivity is linearly dependent on magnetic field in a single grain. As for the resistivity of grain boundary (GB), namely the resistivity of spin transport across the boundary, it has an exponential relationship with magnetic field in the low-field region. Finally we give the analytical magnetoresistance formulas of polycrystalline, which agree well with the experimental results.