C60 transforms to a polymeric phase where the C60 molecules are bonded to form a chain structure when it is subjected to ultraviolet radiation at ambient temperature in the absence of oxygen. The electron paramagnetic resonance spectrum of C60 photolyzed in the presence of a low pressure of oxygen or in air shows a very broad, asymmetric derivative signal at room temperature and at a magnetic field position well removed from g=2.000. With decreasing temperature, the broad line shifts to lower magnetic fields and increases further in linewidth, as expected for a ferromagnetic resonance signal. A low-field nonresonant derivative signal is also observed, consistent with the existence of ferromagnetism. Ferromagnetism up to room temperature in photolyzed C60 is confirmed unequivocally by superconducting quantum interference device measurements of the dc magnetization as a function of magnetic field. A possible model for the origin of ferromagnetism based on these results and Raman data on photolyzed samples is also proposed.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jan 15 2004|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics