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Giant coercivity in a one-dimensional cobalt-radical coordination magnet
Norio Ishii1, Yoshitomo Okamura, Susumu Chiba
1Department of Applied Physics and Chemistry and Course of Coherent Optical Science, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan. ishi@pc.uec.ac.jp
Journal of the American Chemical Society
|December 14, 2007
Summary
A novel metal-radical polymer exhibits the highest coercive field ever recorded, functioning as an exceptionally hard magnet at low temperatures. However, its magnetic properties transition to soft above 10 K due to rapid magnetization changes.
Area of Science:
- Materials Science
- Magnetism
- Polymer Chemistry
Background:
- Development of advanced magnetic materials is crucial for technological innovation.
- Metal-radical polymers offer unique magnetic properties due to unpaired electron spins.
- Understanding the temperature dependence of magnetic behavior is key to material application.
Purpose of the Study:
- To synthesize and characterize a novel metal-radical polymer.
- To investigate the magnetic properties, particularly coercivity, of the synthesized polymer.
- To explore the temperature-dependent magnetic behavior and magnetization dynamics.
Main Methods:
- Synthesis of the cobalt(II) bis(hexafluoroacetylacetonate)-bis(pyridyl)nitronyl-nitroxide radical polymer ([Co(hfac)2.BPNN]).
- Magnetic property measurements including hysteresis loops to determine coercive field.
- Temperature-dependent magnetic susceptibility and magnetization studies.
Main Results:
- The metal-radical polymer [Co(hfac)2.BPNN] demonstrated a record-breaking coercive field of 52 kOe (4.1 MA m-1) at 6 K.
- This exceptional coercivity classifies the material as the hardest magnet reported to date.
- Above 10 K, the material exhibited soft magnetic characteristics attributed to fast magnetization reorientation dynamics.
Conclusions:
- The synthesized metal-radical polymer represents a significant advancement in hard magnetic materials.
- The temperature-dependent transition from hard to soft magnetism highlights the dynamic nature of its magnetic state.
- Further research into controlling magnetization dynamics could lead to new applications in magnetic storage and spintronics.
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