Interfacial reconstruction in La0.7Sr0.3MnO3 thin films: giant low-field magnetoresistance.

Herein, interfacial reconstruction in a series of La0.7Sr0.3MnO3 (LSMO) films grown on a (001) oriented LaAlO3 (LAO) substrate using the pulsed plasma sputtering technique is demonstrated. X-ray diffraction studies suggested that the LSMO film on LAO was stabilized in a tetragonal structure, which was relaxed in-plane and strained along the out-of-plane direction. The interfacial reconstruction of the LSMO-LAO interface due to the reorientation of the Mn ion spin induced spin-glass behavior due to the presence of non-collinear Mn ion spins. Consequently, the interface effect was observed on the Curie temperature, temperature-dependent resistivity, metal-to-semiconductor transition temperature, and magnetoresistance (MR). At a magnetic field of 7 T, MR decreased from 99.8% to 7.69% as the LSMO film thickness increased from 200 Å to 500 Å. A unique characteristic of the LSMO films is the large low-field MR after a decrease in the field from the maximum field. The observed temperature-dependent magnetization and low-temperature resistivity upturn of the LSMO films grown on LAO provide direct evidence that the low-field MR is due to the non-collinear interfacial spins of Mn. The present work demonstrates the great potential of interface and large low-field MR, which might advance the fundamental applications of orbital physics and spintronics.

Apparatus and method for the growth of epitaxial complex oxides on native amorphous SiO2 surface of (001) oriented single crystal silicon.

The design, fabrication, and performance of an apparatus for the deposition of complex oxides with highly uniform thicknesses at controllable deposition rates over large area, even on the native amorphous SiO2 layer of (001) oriented single crystal Si, are described. The apparatus makes use of the lateral port of a spherical chamber. The port is maintained at uniform temperature, and it houses a substrate heater. The deposition process is controlled by varying different parameters such as target-to-substrate distance, sputtering power, sputtering gas atmosphere, substrate temperature, and pulsed plasma growth. The system has been tested by growing a series of La0.7Sr0.3MnO3 thin films on Si. The systematic strain relaxation and thus the tunable magnetic properties along with the presence of high-quality surface morphology of the films indicate that the designed system could be used to fabricate different components of oxide electronics-based devices over larger area.