Large, Temperature-Tunable Low-Field Magnetoresistance in La_(0.7)Sr_(0.3)MnO_3:NiO Nanocomposite Films Modulated by Microstructures

摘要

Magnetic properties and low-field magnetoresistance (LFMR) in La_(0.7)Sr_(0.3)MnO_3 (LSMO):NiO nanocomposite films grown on SrTiO_3 (001) substrates, which are shown to be tunable with different microstructures, are investigated. The LSMO:NiO nanocomposite films with NiO volume ratio of 50% have a checkerboard-like structure and show a large LFMR in a temperature range from 200 to 300 K (≈17% at 250 K with a magnetic field of 1 T). As the NiO volume ratio is increased to 70%, a nano-columnar structure formed in the films. Their LFMR is significantly enhanced at a wide temperature range of 10-210 K. The highest value of LFMR with 41% is achieved at 10 K in a magnetic field of 1 T. The enhanced LFMR can be considered to result from the electron scattering at the ferromagnetic LSMO/NiO interfaces and magnetic tunnel junctions (MTJs) of LSMO/NiO/LSMO at the nanometer scale. These results demonstrate that large and tunable LFMR from low temperature to room temperature can be realized by controlling the microstructures in the epitaxial La_(0.7)Sr_(0.3)MnO_3:NiO nanocomposite thin films, which will be expected to be applied in the devices using for a wide temperature range.