5393www.MaterialsViews.com wileyonlinelibrary.com environment. [ 9,10 ] Recently, due to the deepening cognition of the intrinsic and extrinsic GMR effect, growing attention has been paid to polycrystalline manganites to obtain the extrinsic low-fi eld magnetoresistance (LFMR) by structuring grain boundaries, nanosized inclusions, interface phase, and artifi cial grain boundaries. What's more, the LFMR in composites or fi lms can be further improved by introducing a secondary phase (usually non-magnetic or antiferromagnetic insulators). [11][12][13][14][15][16][17][18][19][20] For example, the LFMR values of -6% at 5 K and 0.16 T in LSMO:SrTiO 3 superlattice structure, [ 3 ] -17.5% at 30 K and 1 T in LSMO:ZnO columnar structure, [ 21 ] -8% at 10-150 K and 1 T in LSMO:MgO nanorod arrays structure [ 22 ] and -12% at 77 K and 0.4 T in LSMO:Ag 0-3 structure [ 23 ] have been reported. However, neither the early results obtained from LSMO polycrystalline fi lms [ 24 ] or recent results obtained from LSMO:ZnO composite fi lms with a columnar structure, [ 21 ] enhanced LFMR values are always display in a low temperature range. That may be due to the large grain size in polycrystalline fi lms (≈µm) or weak spin coupling at the phase boundaries in the composite thin fi lms. Systems featuring a large LFMR at temperatures close to or even higher than room temperature are also interesting owing to their potential applications in magnetic fi eld sensing and data storage. [ 25 ] Dey et al. have found that the large LFMR will keep steady in a higher temperature range when the grain size is in nanoscale and gets pronounced with the decrease in particle size. [ 26 ] It is notable that the spin pinned effect occurs at the nanosized grain surface defect sites or spin coupling at the boundaries. [ 26,27 ] In addition, the short range ferromagnetic (FM) coupling order may add the opportunity of spin scattering even near the Curie temperature. [ 28,29 ] Thus it is speculated that the high-temperature LFMR in LSMO composite fi lms can be got through tuning the grain size and the FM coupling at the phase boundary. MacManus-Driscoll et al. proposed that the self-assembled composite fi lms are free from substrate clamping constraints and form strained vertical interface areas which can be used to tune the FM coupling by another phase and also can provide a more fl exible way to control the growth of the fi lms which can be used to control the grain size to get enhanced physical properties. [ 30 ] To prepare the LSMO-based composite fi lms, on the one hand, it should NiO nano composite thin fi lms, which will be expected to be applied in the devices using for a wide temperature range.