Co nanoparticle films were prepared by plasma-gas-condensation-type particle beam deposition system. High-resolution transmission electron microscopy images show that the Co nanoparticles have a very narrow size distribution with an average diameter of ∼20nm, and each of the Co nanoparticles is covered with an ∼3nm layer of CoO. Hysteresis loops of the films after field-cooling in a 5T magnetic field are greatly shifted, which can be attributed to the exchange bias effect caused by the interfacial exchange coupling between the CoO shell and the Co core. The zero field cooled films show several prominent properties, such as a quite large coercive field, a small remanence and their abnormal dependences on temperature. All these observations can be attributed to the existence of an exchange bias effect within each single Co nanoparticle even without a field-cooling process.
- Coercive field
- Exchange bias effect
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics