The magnetoresistance effects(H=0.75T) and the transportation characteristice (H=0T) of La o.67 Sr 0.33 MnO 3+δ /Pr 0.7 Ca 0.3 MnO 3+δ /La o.67 Sr 0.33 MnO 3+δ trilayer filmsh have been studied.With the thickness of middle-layered changing
the resistivity of trilayer films shows greater decrease than the single layered La o.67 Sr 0.33 MnO 3+δ films
the MR values are decreased under 0.75T
and the thermal activation energy E c is decreased and disappeared at lower temperature.This imply that the middle-layered not only induces the intra-magnetic field but also induces the density of states between the LSMO's gap in the trilayered films.