  The transport and magnetic properties in ferromagnetic manganese-oxide thin
films are studied based on the model of the coupling between the mobile
d-electrons and the core spins in Mn ions. The spontaneous magnetization and
the resistivity are obtained for various magnetic fields and temperature. The
resistivity in absence of magnetic field and the magnetoresistance exhibit
maxima near the Curie temperature, the applied magnetic field moves the
position of the resistivity peak to high temperature and suppresses the peak
value, which agree with the experimental results. The Hall resistivity is
predicted to exhibit maximum near the Curie point. The pressure effect of the
magnetoresistance can also be explained qualitatively in this mechanism. The
colossal magnetoresistance in ferromagnetic manganese-oxide thin films is
attributed to the spin-correlation fluctuation scattering and the low
dimensional effect.
