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"Live" surface ferromagnetism in Fe nanodots/Cu multilayers on Cu(111).
1Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Physical Review Letters
|December 31, 2005
Summary
We observed a magnetic phase transition from ferromagnetic to spin-glass-like behavior in stacked iron nanodot layers. Surface iron nanodots surprisingly remain ferromagnetic at higher temperatures due to unique surface coupling.
Area of Science:
- Condensed matter physics
- Materials science
- Surface science
Background:
- Multilayers of magnetic nanodots are crucial for advanced magnetic storage.
- Understanding the transition from 2D to 3D magnetic behavior is key for device optimization.
Purpose of the Study:
- Investigate the dimensional crossover in magnetic nanodot multilayers.
- Characterize the magnetic phase transition and surface ferromagnetism.
Main Methods:
- Fabrication of iron nanodot multilayers on a Cu(111) substrate with copper spacing layers.
- In situ magneto-optical Kerr effect measurements to probe magnetic properties.
Main Results:
- Observed a ferromagnetic to spin-glass-like phase transition with increasing Fe dot layers.
- The topmost Fe nanodot layer exhibits unusual surface ferromagnetism.
- Surface ferromagnetism shows a higher critical temperature than the bulk spin-glass phase.
Conclusions:
- Surface-state-mediated coupling drives robust ferromagnetism in the topmost layer.
- The dimensional crossover influences magnetic ordering and surface properties.
- This study reveals novel magnetic behavior at the nanoscale.