Structural and magnetic properties of polymerized C60 with Fe

Abstract

We provide evidence that high-pressure high-temperature (2.5 GPa and 1040 K) treatment of mixtures of iron with fullerene powders leads to the complete transformation of iron into iron carbide Fe3C. The comparison of the magnetic properties (Curie temperature and magnetic moment) of the here studied samples and those for the ferromagnetic polymer Rh-C60 indicates that the main ferromagnetic signal reported in those samples is due to Fe3C and not related to the ferromagnetism of carbon as originally interpreted. Taking into account the results obtained in this study the original paper on "Magnetic carbon" (Nature 413, 716 (2001)) was recently retracted.

Magnetic order in graphite: Experimental evidence, intrinsic and extrinsic difficulties

“…The nowadays technique allows us to measure the amount of magnetic impurities with high enough accuracy especially in carbon-based materials. However, inappropriate sample handling added to the possibility of non-simple phase transformations of magnetic elements after sample preparation (as in the case of magnetic fullerene [7,8]), possible aging effects as well as the rather small magnetic signals of the magnetic carbon samples, make the research in this area of magnetism rather difficult.…”

Giant Moment Enhancement of Magnetic Nanoparticles Embedded in Multi-Walled Carbon Nanotubes: Consistent with Ultrahigh Temperature Superconductivity

“…On the other hand, Dzwilewski et al Talyzin et al (2007) show that the observed high-temperature ferromagnetism in rhombohedral C 60 Makarova et al (2001) is not intrinsic but caused by contamination of magnetic impurities. In addition to the observation of unusual high-temperature ferromagnetism in the carbon-based materials, there was a report of extra magnetic moment induced in graphite due to a large magnetic proximity effect between graphite and magnetic nanoparticles Coey et al (2002).…”

Weak antiferromagnetic superexchange interaction in fcc C60Hn

“…The results demonstrate that the underlying mechanism of the magnetic order in fcc C 60 H n is associated with the AFM superexchange between the magnetic moments created by H dopants. The observation of ferromagnetism in fullerenes has attracted intensive attention due to its interest concerning carbon magnetism and potential technological application in the emerging field of spintronics.1-5 However, there has long been controversy about whether the origin of the observed ferromagnetism is associated with extrinsic iron impurities [6][7][8] or intrinsic defects.9-14 The latter intrinsic defects involve carbon vacancies in polymerized fullerenes 9-11 or doped fullerenes 12-14 C 60 R n (R: nonmagnetic elements such as H and O atoms) where doping creates fullerene radical adducts with unpaired spins localized on fullerene. Experimental studies for photo-oxidated fullerenes 3,4 and hydrofullerite 5 C 60 H 24 observed a signal of ferromagnetism at room temperature.…”

“…1-5 However, there has long been controversy about whether the origin of the observed ferromagnetism is associated with extrinsic iron impurities [6][7][8] or intrinsic defects.…”

“…[1][2][3][4][5] However, there has long been controversy about whether the origin of the observed ferromagnetism is associated with extrinsic iron impurities [6][7][8] or intrinsic defects. [9][10][11][12][13][14] The latter intrinsic defects involve carbon vacancies in polymerized fullerenes [9][10][11] or doped fullerenes [12][13][14] C 60 R n (R: nonmagnetic elements such as H and O atoms) where doping creates fullerene radical adducts with unpaired spins localized on fullerene.…”