Large, Temperature‐Tunable Low‐Field Magnetoresistance in La 0.7 Sr 0.3 MnO 3 :NiO Nanocomposite Films Modulated by Microstructures

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.