Oscillatory Angular Dependence of Exchange Bias for Epitaxial NiO-Co (001) Bilayers
Abstract
We have sputter-deposited NiO-Co bilayers on MgO (001) substrates. NiO grows epitaxially on MgO at 900 deg C and subsequently the room deposited 80 A thick Co films have a fcc crystal structure in epitaxy with the oxide underlayer. These samples were warmed up to 300 deg C and then zero-field or field cooled through the NiO Neel temperature (a 300 Oe magnetic field was applied along the 100 or the 110 MgO axis). Magnetic hysteresis loops were obtained by magneto-optical Kerr effect, the magnetic field being oriented in the plane of the substrate for various angles alpha with respect to the 100 direction. The usually expected behavior for such experiments is a smooth angular a dependence of the exchange bias H(sub E) close to a cosine with only one sign change over 180 deg. The high crystallographic coherence of our NiO/Co bilayers induces a very unusual oscillatory HE (alpha) dependence with several sign changes according to the NiO axis field application. Despite of the Co magnetization switching mechanism which is not a pure coherent rotation. we propose a Stoner-Wohlfhart model including four fold anisotropy and unidirectional exchange anisotropy giving a realistic description of these typical magnetic properties.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2001
- Accession Number
- ADP012264
Entities
People
- B. Warot
- E. Snoeck
- J. C. Ousset
- J. F. Bobo
- S. Dubourg
Organizations
- National Center for Scientific Research