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Two-dimensional surface magnetism in the bulk paramagnetic intermetallic alloy CoAl(100)
V Rose1, K Brüggemann, R David
1Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, USA. vrose@anl.gov
Physical Review Letters
|March 16, 2007
Summary
The CoAl (100) surface exhibits two-dimensional ferromagnetism, behaving like a finite-size 2D XY system. This magnetism arises from cobalt antisite atoms on the surface, with a Curie temperature of 90 K.
Area of Science:
- Surface science
- Condensed matter physics
- Magnetism
Background:
- Bulk paramagnetic Cobalt-Aluminum (CoAl) is a metallic alloy with potential for surface magnetism.
- Understanding surface magnetic properties is crucial for developing novel magnetic materials and devices.
Purpose of the Study:
- To investigate the magnetic behavior of the (100) surface of B2 CoAl.
- To characterize the nature of ferromagnetism at the surface and identify its origin.
Main Methods:
- In situ magneto-optical Kerr effect (MOKE) measurements.
- Scanning tunneling microscopy (STM) and spectroscopy (STS) for surface characterization.
Main Results:
- The CoAl (100) surface behaves as a two-dimensional ferromagnet.
- The critical exponent beta was determined to be 0.22 ± 0.02, indicative of 2D XY universality.
- A Curie temperature (Tc) of 90 K was observed.
- Surface magnetism is attributed to the presence of Cobalt antisite atoms.
Conclusions:
- The CoAl (100) surface is an excellent model system for studying two-dimensional ferromagnetism.
- The observed behavior aligns with finite-size 2D XY universality.
- Cobalt antisite defects are responsible for the surface magnetism.
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