Magnetism of Carbon‐Based Materials

Abstract

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Tailoring the induced magnetism in carbon-based and non-traditional inorganic nanomaterials

“…However, this is in contradistinction with the Ga(Mn)As case where a full compensation of carriers occurs using Sn as a donor and turns the ferromagnetic coupling among the Mn atoms into an antiferromagnetic one [23]. These observations may also be related to the important issue associated with the presence of defects and impurities and referring to the appearance or not of the metallic feature in the undoped semi-conducting system as a result of doping [24,25]. Presently, the issue of whether the metallic state is a necessary stage for magnetic features to appear in these systems has not been answered conclusively [26,23].…”

Magnetic carbon: Explicit evidence of ferromagnetism induced by proton irradiation

“…Some of the published work, cited in the introduction and reviewed in Ref. [16], as well as the recently published work on HOPG [1,2] and fullerenes [3] are examples that indicate that not all the room-temperature ferromagnetism can be simply due to impurities. We think that the results obtained in HOPG after proton irradiation by two independent techniques clearly support the existence of ferro(ferri)magnetism in carbon without involving metallic impurities and can be considered as final evidence.…”

Ferromagnetism of a graphite nodule from the Canyon Diablo meteorite

“…To put the weakness of the ferromagnetism in perspective, carbon with a ferromagnetic moment of 1 µ B per atom would have σ s = 465 Am 2 kg -1 , and a corresponding polarization J s = 1.2 T. It seems that only a tiny fraction of the carbon atoms participate in the magnetism of these materials, or else the carbon moment must be remarkably weak (~ 10 -4 µ B ). An exception is amorphous carbon prepared by direct pyrolysis 3 , which in one case 9 was reported to have a room-temperature magnetization of 9.2 Am 2 kg -1 , or 0.02 µ B per carbon. We have reproduced this result, but find iron in the form of micron-sized oxide particles dispersed throughout the carbon.…”