Abstract
Exchange-coupled bilayer systems consisting of a polycrystalline ferromagnetic Fe layer grown on an epitaxial antiferromagnetic layer have been prepared by molecular beam epitaxy and investigated by conversion electron Mössbauer spectroscopy and superconducting quantum interference device magnetometry. The systems show a significant exchange bias effect at low temperatures. Tracer layers of (in the Fe layer) and (in the layer) have been placed in the samples in order to probe the spontaneous spin orientation at different distances from the interface. The Fe spins in the ferromagnetic layer are preferentially oriented in the interfacial plane. In as-prepared samples the presence of the Fe top layer induces a striking out-of-plane component of the interfacial Fe spins in the antiferromagnetic film. This perpendicular component decreases in magnitude at a larger distance from the interface. A reorientation transition from out-of-plane toward in-plane spin orientation was observed in the interfacial layer with increasing age of the sample. This effect is correlated with an increased magnitude of the exchange bias field for the aged samples.
- Received 28 December 2004
DOI:https://doi.org/10.1103/PhysRevB.72.064440
©2005 American Physical Society