Nature 413, 716–718 (2001)

In this Letter we reported high-temperature ferromagnetism in a polymeric phase of pure carbon that was purportedly free of ferromagnetic impurities¹. Since then, however, measurements made on the same and similar samples using particle-induced X-ray emission (PIXE) with a proton microbeam have indicated that these had considerable iron content^{2, 3, 4}. Also, polymerized C₆₀ samples mixed with iron before polymerization had a similar Curie temperature (500 K) to those we described¹, owing to the presence of the compound Fe₃C (cementite)⁵. In addition, it has since been shown that the pure rhombohedral C₆₀ phase is not ferromagnetic⁶.

 Nevertheless, magnetic order in impurity-free graphitic structures at room temperature has been demonstrated independently⁷ (before and after publication of ref. 1). Ferromagnetic properties may yet be found in polymerized states of C₆₀ with different structural defects and light-element (H, O, B, N) content⁸.

T.L.M. and P.S. decline to sign this retraction because they do not believe that the earlier results¹, supported in subsequent studies^{9, 10}, are totally invalidated by these findings^{2, 3, 4, 5, 6}.

References

1. Makarova, T. L. et al. Magnetic carbon. Nature 413, 716–718 (2001); corrigendum 436, 1200 (2005).
2. Höhne, R. & Esquinazi, P. Can carbon be ferromagnetic? Adv. Mater. 14, 753–756 (2002) | Article | ISI |
3. Spemann, D. et al. Evidence for intrinsic weak ferromagnetism in a C₆₀ polymer by PIXE and MFM. Nucl. Instrum. Meth. B 210, 531–536 (2003) | Article | ISI |
4. Han, K. H. et al. Observation of intrinsic magnetic domains in C₆₀ polymer. Carbon 41, 785–795 (2003); addendum 431, 2425–2426 (2003) | Article | ISI |
5. Talyzin, A. , Dzwilewski, A. , Drubovinsky, L. , Setzer, A. & Esquinazi, P. Magnetic properties of polymerized C₆₀ with Fe. Preprint at http://arXiv.org/abs/cond-mat/0602306
6. Boukhvalov, D. W. et al. Testing the magnetism of polymerized fullerene. Phys. Rev. B 69, 115425 (2004) | Article |
7. Makarova, T. & Palacio, F. (eds) Ch. 24 Carbon-based Magnetism (Elsevier, Amsterdam, 2006)
8. Makarova, T. L. et al. Magnetism in photopolymerized fullerenes. Carbon 41, 1575–1584 (2003) | Article | ISI |
9. Narozhnyi, V. N. et al. Ferromagnetic carbon with enhanced Curie temperature. Physica B 329, 1217–1218 (2003) | Article | ISI |
10. Wood, R. A. et al. Ferromagnetic fullerene. J. Phys. Condens. Matter 14, L385–L391 (2002) | Article | ISI |

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