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Phys. Rev. B 70, 054407 (2004) [9 pages]

Unconventional magnetism in all-carbon nanofoam

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A. V. Rode1,*,†, E. G. Gamaly1, A. G. Christy2, J. G. Fitz Gerald3, S. T. Hyde1, R. G. Elliman1, B. Luther-Davies1, A. I. Veinger4, J. Androulakis5, and J. Giapintzakis5,6,*,‡
1Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia
2Department of Earth and Marine Science, Australian National University, Canberra, ACT 0200, Australia
3Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
4Ioffe Physical-Technical Institute, Polytechnicheskaya 26, St. Petersburg, Russia
5Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Lasers, P.O. Box 1527, Vasilika Vouton, 71110 Heraklion, Crete, Greece
6Department of Materials Science and Technology, University of Crete, P.O. Box 2208, 710 03 Heraklion, Crete, Greece

Received 11 September 2003; revised 28 May 2004; published 17 August 2004

We report production of nanostructured magnetic carbon foam by a high-repetition-rate, high-power laser ablation of glassy carbon in Ar atmosphere. A combination of characterization techniques revealed that the system contains both sp2 and sp3 bonded carbon atoms. The material is a form of carbon containing graphite-like sheets with hyperbolic curvature, as proposed for “schwarzite.” The foam exhibits ferromagnetic-like behavior up to 90 K, with a narrow hysteresis curve and a high saturation magnetization. Such magnetic properties are very unusual for a carbon allotrope. Detailed analysis excludes impurities as the origin of the magnetic signal. We postulate that localized unpaired spins occur because of topological and bonding defects associated with the sheet curvature, and that these spins are stabilized due to the steric protection offered by the convoluted sheets.

© 2004 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.70.054407
DOI:
10.1103/PhysRevB.70.054407
PACS:
75.75.+a, 78.67.Bf, 81.15.Fg, 61.46.+w

*Authors to whom correspondence should be addressed.

†Electronic address: avr111@rsphy1.anu.edu.au

‡Electronic address: giapintz@iesl.forth.gr

 
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