Effect of the substrate crystalline structure on the magnetic, electrical,and crystallographic characteristics of La0.35Nd0.35Sr0.3MnO3 epitaxial films

A study has been made of the electrical resistivity rho, magnetoresistance Delta rho/rho, and magnetization of La0.35Nd0.35Sr0.3MnO3 epitaxial films o n ZrO2(Y2O3), SrTiO3, LaAlO3, and MgO substrates. The first film can exist in four equivalent crystallographic orientations in the sample plane, while the other three have only one orientation. The maxima of rho and Delta rho /rho of the first film are broadened considerably in the vicinity of the Cu rie point T-C compared to the three others, the magnitude of rho itself bei ng larger by 1.5 orders of magnitude, and a large negative magnetoresistanc e (l Delta rho/rho l similar to 10% in a field of 8.4 kOe) is observed at t emperatures 80 less than or equal to T less than or equal to 200 K. In all films, the magnetic moment per molecule at 5 K is similar to 46% smaller th an the pure spin value, due to the existence of magnetically disordered reg ions. The larger value of rho of the film deposited on ZrO2(Y2O3) is due to the electrical resistance of the boundaries separating regions with differ ent crystallographic orientations, and the magnetoresistance is associated with polarized carriers tunneling through the boundaries coinciding with do main walls. The low-temperature magnetoresistance in fields above technical saturation is caused by the strong p-d exchange coupling within spin-order ed regions. (C) 2000 MAIK "Nauka/Interperiodica".