Enhanced magnetoresistance in self-assembled monolayer of oleic acid molecules on Fe3O4 nanoparticles

Spin transport through molecules is investigated using self-assembled monolayers of oleic acid molecules on half metallic Fe3O4 nanoparticles. Fourier transform infrared spectroscopy measurements indicate that 1 ML (monolayer) molecules chemically bond to the Fe3O4 nanoparticles and the physically absorbed molecules do not exist in the samples. The magnetoresistance (MR) of cold-pressed, molecule fully covered nanoparticles is up to 7.3% at room temperature and 17.5% at 115 K under a field of 5.8 kOe. The MR ratio is more than two times larger than that of pure Fe3O4 nanoparticles. This enhanced MR is likely arising from weak spin scattering while carriers hop through the oleic acid molecules. These results show that small molecules are promising for development of future spin-based molecular electronics.