Defect-induced ferromagnetism in fullerenes |
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Authors: | D W Boukhvalov and M I Katsnelson |
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Institution: | (1) Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525AJ Nijmegen, The Netherlands |
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Abstract: | Based on the ab initio electronic structure calculations the
picture of ferromagnetism in polimerized C60 is proposed
which seems to explain the whole set of controversial experimental
data. We have demonstrated that, in contrast with cubic
fullerene, in rhombohedral C60 the segregation of iron atoms
is energetically unfavorable which is a strong argument in favor
of intrinsic character of carbon ferromagnetism which can be
caused by vacancies with unpaired magnetic electrons. It is shown
that: (i) energy formation of the vacancies in the rhombohedral
phase of C60 is essentially smaller than in the cubic phase,
(ii) there is a strong ferromagnetic exchange interactions between
carbon cages containing the vacancies,
(iii) presence of iron impurities can diminish essentially
the formation energy of intrinsic defects, and (iv) the fusion of the
magnetic single vacancies into nonmagnetic bivacancies is energetically
favorable. The latter can explain a fragility of the ferromagnetism. |
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Keywords: | PACS" target="_blank">PACS 75 75 +a Magnetic properties of nanostructures 71 20 Tx Fullerenes and related materials intercalation compounds 61 48 -c Structure of fullerenes and related hollow molecular clusters |
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