12-15 July 2011
Saint George Hotel
Africa/Johannesburg timezone

Magnetic properties of carbon nanospheres at low temperatures

13 Jul 2011, 12:00


Oral Presentation Track A - Condensed Matter Physics and Material Science CMPMS2


Mr Makhosonke Dubazane (University of the Witwatersrand)


The magnetic and electrical properties of nitrogen doped carbon nanospheres can be probed using Electron Magnetic Resonance (EMR) techniques. Previous Raman spectroscopy studies show that both the pristine and doped spheres are graphitic in character. However, XRD measurement showed that these spheres consist of graphitic crystallites embedded in an amorphous phase. Previous ESR measurements showed large peak on nitrogen doped spheres, implying that the nitrogen occupies substitutional sites in graphitic lattice. The EMR measurements clearly showed large Curie-type paramagnetism at low temperatures for all the samples investigated. The EMR peak-to-peak linewidth have provided evidence of the phonon bottleneck effect in one of the sample investigated, meaning to say that there is a strong interaction between localized and conduction electrons. The broadening of linewidth may be manifested by a Korringa type interaction whereby the spin-lattice relaxation time T1 is inversely proportional to the temperature. The sample with the highest concentration of nitrogen behaves very differently from the other samples studied in th temperature range 77 K to 300 K, and this behaviour is not well understood at present. This may involve contributions from electron scattering with stationary nitrogen impurities, and therefore different spin relaxation mechanisms which are related to the Elliot and Yafet mechanisms.

Level (Hons, MSc, <br> &nbsp; PhD, other)? MSc
Consider for a student <br> &nbsp; award (Yes / No)? Yes
Would you like to <br> submit a short paper <br> for the Conference <br> Proceedings (Yes / No)? Yes

Primary author

Mr Makhosonke Dubazane (University of the Witwatersrand)


Dr Jonathan Keartland (University of the Witwatersrand) Mr Yosief Mishgina (University of the Witwatersrand)

Presentation Materials