Spin-transfer mechanism of ferromagnetism in polymerized fullerenes:<i>Ab initio</i>calculations

Kvyatkovskiĭ, O. E.; Zakharova, I. B.; Shelankov, A. L.; Makarova, T. L.

doi:10.1103/physrevb.72.214426

Cited by 26 publications

(18 citation statements)

References 47 publications

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“…The calculations have shown that the best dopant for obtaining high spin states in fullerenes is hydrogen provided that the C 60 :H ratio is unity [1]. However, fullerene C 60 tends to form compounds with large 'magic' numbers like C 60 H 24 and C 60 H 36 which do not have unpaired spins.…”

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confidence: 98%

“…For the singly bonded dimer the A g (2) is positioned at 1451 cm À1 [4]. Other features in the spectra which speak in favour of single bonding, are the splitting of the H g (1), shift of A g (1) and awakening of the G d (2) mode at 623 cm À1 [4]. We can conclude that the following processes take place: during first minutes the hydrogenated fullerenes polymerize by the [2þ2] cycloaddition scheme, forming dimers and linear chains identified by the shift if the A g (2) mode to the 1464 and 1459 positions (Fig.…”

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confidence: 99%

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Experimental realization of high spin states in dilutely hydrogenated fullerenes

Makarova

Zakharova

Kvyatkovskiĭ

et al. 2009

Physica Status Solidi (b)

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A novel method for preparing dilutely hydrogenated fullerenes H:C 60 is presented. DFT calculations of the Raman spectra at the B3LYP/3-21G level are compared with the experimental data. Under the laser treatment these phases form a rich variety of dimeric and polymeric structures, quite in contrast to pristine C 60 which forms dimers and polymers bonded through the [2 þ 2] addition, and in contrast to heavily hydrogenated fullerenes which do not polymerize at all. Dilutely hydrogenated fullerenes polymerize differently, forming both double bonded structures and single bonded dimers. We have shown that dilute hydrogenation of C 60 creates large amount of unpaired spins which disappear due to the formation of diamagnetic single bonded dimers.

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confidence: 98%

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confidence: 99%

Experimental realization of high spin states in dilutely hydrogenated fullerenes

Makarova

Zakharova

Kvyatkovskiĭ

et al. 2009

Physica Status Solidi (b)

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“…Refs. (Kvyatkovskii 2005, Kvyatkovskii 2006) consider the situation when C 60 molecule is doped through the presence of structural defects and impurities which create stable molecular ions C 60 ± and analyze the interaction of two adjacent molecules (i.e. dimer) embedded in a twodimensional polymeric network.…”

Section: 8magnetic Nature Of Intrinsic Carbon Defectsmentioning

confidence: 99%

ChemInform Abstract: Nanomagnetism in Otherwise Nonmagnetic Materials

Makarova

2010

ChemInform

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“…[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. Experimental studies for photo-oxidated fullerenes 3,4 and hydrofullerite 5 C 60 H 24 observed a signal of ferromagnetism at room temperature.…”

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Weak antiferromagnetic superexchange interaction in fcc C60Hn

et al. 2012

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A recent density-functional calculation for fcc C 60 H n (n = odd) [K. W. Lee and C. E. Lee, Phys. Rev. Lett. 106, 166402 (2011)] proposed the existence of Stoner ferromagnetism based on an itinerant band model. However, our density-functional calculation shows that the antiferromagnetic (AFM) configuration is slightly more stable than the ferromagnetic (FM) one. This preference for antiferromagnetism over ferromagnetism is analogous to the case of a dimer (C 60 H) 2 , where each C 60 H is spin polarized by an intramolecular exchange and the two magnetic moments are antiferromagnetically coupled with each other. 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. However, a density-functional theory (DFT) calculation 13 for C 60 O did not support the existence of ferromagnetism, whereas a DFT calculation 14 for fcc C 60 H n predicted a strong itinerant ferromagnetism with odd-numbered H dopants. From their DFT calculation within the local-density approximation, Lee and Lee (LL) 14 found that H dopants on an fcc C 60 crystal create quasilocalized π electrons leading to a narrow half-filled band, and concluded that a direct overlap of the π electrons between adjacent C 60 H n molecules gives rise to Stoner (itinerant) ferromagnetism with an exchange splitting of ∼0.2 eV. However, this exchange splitting is not due to the Stoner-type FM exchange but to an intramolecular exchange (i.e., Stoner parameter I ), as discussed below. As a matter of fact, the ferromagnetic (FM) and antiferromagnetic (AFM) order is governed by the exchange interaction energy between neighboring magnetic moments (i.e., exchange coupling constant J in the Heisenberg model).Recently, it was reported 15 that the microscopic mechanism of defect-induced magnetism in dilute magnetic semiconductors could be similar to that in carbon-based materials such as C 60 polymers, TDAE-C 60 , graphene ribbons, and irradiated graphite. There are two different mechanisms that describe the exchange interaction in diluted magnetic semiconductors: The double-exchange mechanism favors FM coupling, whereas the superexchange mechanism usually leads to AFM co...

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Spin-transfer mechanism of ferromagnetism in polymerized fullerenes:Ab initiocalculations

Cited by 26 publications

References 47 publications

Experimental realization of high spin states in dilutely hydrogenated fullerenes

Experimental realization of high spin states in dilutely hydrogenated fullerenes

ChemInform Abstract: Nanomagnetism in Otherwise Nonmagnetic Materials

Weak antiferromagnetic superexchange interaction in fcc C60Hn

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