Preparation,structure,magneticpropertiesandspecialmagnetoresistanceeffectofLa0.67Sr0.33MnO3+δ/Pr0.7Ca0.3MnO3+δ/La0.67Sr0.33MnO3+δtrilayeredthinfilms

<正> The La0.67Sr0.33MnO3+δ/Pr0.7Ca0.3MnO3+δ/La0.67Sr0.33MnO3+δ（LPL） trilayered films on （100） LaAlO3 substrates are prepared by using direct current （DC） magnetron sputtering method. The results obtained by means of X-ray powder diffractometer show that all films are the high quality epitaxial films. The results gained by SQUID magnetometer indicate that there is a magnetic coupling in the LPL trilayered films. The resistivities of LSMO, PCMO and LPL films are measured using standard four-probe method and analyzed logρ-1/T curve. From the results it is concluded that the middle-layered PCMO which is ferromagnetic may play a role of intra-magnetic field, which weakens the paramagnetism of LSMO film, lowers ρmax and enlarges Tp which is the transition temperature from metal to insulator, just as the applied magnetic field does. And the middle-layered PCMO may induce the change of the density of states in the LSMO's gap. The two reasons above make the resistivity and Tp of