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Field induced biquadratic exchange in hard/soft ferromagnetic bilayers
V K Vlasko-Vlasov1, U Welp, J S Jiang
1Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
Physical Review Letters
|May 1, 2001
Summary
Biquadratic exchange coupling emerges between soft iron (Fe) and hard samarium cobalt (SmCo) thin layers. This phenomenon, driven by magnetization fluctuations, leads to unexpected magnetic reorientation in the Fe layer.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Magnetism
Background:
- Investigating magnetic coupling in heterostructures is crucial for advanced spintronic devices.
- Understanding interfacial magnetic phenomena in soft-hard ferromagnetic bilayers is an active research area.
Purpose of the Study:
- To investigate the emergence of biquadratic exchange coupling between soft Fe and hard SmCo thin layers.
- To elucidate the mechanism behind the unexpected reorientation of Fe layer magnetization.
Main Methods:
- Experimental observation of magnetic behavior in Fe/SmCo thin film bilayers.
- Theoretical modeling based on Slonczewski's fluctuating exchange mechanism.
Main Results:
- Biquadratic exchange coupling was observed between soft Fe and hard SmCo thin layers.
- Remanent magnetization in the Fe layer unexpectedly reoriented from parallel to perpendicular to the SmCo easy axis under a negative magnetic field.
- A model was proposed where partial remagnetization of the hard SmCo layer induces magnetization fluctuations, leading to biquadratic coupling via intralayer exchange averaging in the soft Fe layer.
Conclusions:
- The study successfully explains the observed biquadratic coupling and magnetization reorientation using a fluctuating exchange mechanism.
- The findings provide insights into the complex interfacial magnetic interactions in soft-hard ferromagnetic bilayers.