Substrate-dependent microstructure and magnetoresistance of La-Sr-Mn-O thin films grown by rf sputtering

The relationship between the microstructure and 'the magnetoresistive prope rties of La-Sr-Mn-O thin films was investigated. La0.76Sr0.24Mn0.98O3-delta films were deposited onto (100) SrTiO3, (100) LaAlO3, (110) sapphire and p olycrystalline YSZ substrates by rf sputtering. The films grew epitaxilly o n SrTiO3 and LaAlO3 substrates with a large number of defects, whereas in-p lane-oriented and nonoriented polycrystalline films with 20-60 nm grains gr ew on the sapphire and polycrystalline YSZ substrates, respectively. The ma gnetoresistance ratio (H = 0.8 T) of the epitaxial films has a peak at a te mperature slightly below the maximum resistance temperature. The resistivit y Of the epitaxial films was ten times less than that of the polycrystallin e films. The polycrystalline films exhibited substantial magnetoresistance ratios over a wide temperature range. The existence of grain boundaries and the preferential in-plane grain orientation were found to be correlated to the resistivity, temperature dependence and low magnetic field sensitivity of magnetoresistance.