Defect-induced ferromagnetism in fullerenes
Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525AJ Nijmegen, The Netherlands
Corresponding author: a D.Bukhvalov@science.ru.nl
Revised: 17 February 2009
Published online: 1 April 2009
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.
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
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009