Abstract
magnetic nanoparticles, with a very high surface to volume ratio, exhibit both strong exchange anisotropy and magnetic training effect. At the same time high field irreversibility in curves and zero field cooled–field cooled (ZFC-FC) processes has also been detected. A low temperature spin-glass-like transition is evidenced at with strong irreversibility even at . evolves following the well known de Almeida–Thouless line . The thermal dependence of the exchange anisotropy field is described by the random-field model of exchange anisotropy. In the framework of this theory, a surface spin-glass layer about 0.6 nm thick is determined.
- Received 5 August 1997
DOI:https://doi.org/10.1103/PhysRevLett.80.181
©1998 American Physical Society