Magnetically operated nanorelay based on two single-walled carbon nanotubes filled with endofullerenes Fe@C20 (original) (raw)

Electronic and magnetic properties of small fullerene carbon nanobuds: A DFT study

Materials Research Express

The electronic and magnetic properties of carbon nanobuds have been investigated using density functional theory. The carbon nanobuds are formed by attaching smaller fullerenes (C20, C28, C36 and C40) of variable size with (5,5) ACNT and (5,0) ZCNT. Fullerenes interact strongly with CNT surface having binding energies within the range-0.93eV to-4.06eV. The CC bond lengths near the attachment region increase from the original CC bond lengths. The relative stabilities of the nanobuds are closely related to CC bond lengths and bond angles in cycloaddition reaction. Nanobuds formed by bond cycloaddition are energetically most favorable amongst all cycloadditions. The electronic and magnetic properties of nanobuds depend strongly on electronic properties of its building blocks. The attachment of C20 and C40 on CNTs open up the HOMO-LUMO gaps of nanobuds whereas C28 and C36 results in addition of impurity states near the Fermi level. The total magnetic moment of nanobuds vary from 0.28µB to 4.00µB which depend on the nature of bonding between fullerene and CNTs. The results outline the potential of nanobuds as hybrid carbon nanostructures and how their properties can be tuned with the size and type of fullerene attached.

Magnetic Fullerenes inside Single-Wall Carbon Nanotubes

C59N magnetic fullerenes were formed inside single-wall carbon nanotubes by vacuum annealing functionalized C59N molecules encapsulated inside the tubes. A hindered, anisotropic rotation of C59N was deduced from the temperature dependence of the electron spin resonance spectra near room temperature. Shortening of the spin-lattice relaxation time T1 of C59N indicates a reversible charge transfer toward the host nanotubes above ∼350 K. Bound C59N−C60 heterodimers are formed at lower temperatures when C60 is coencapsulated with the functionalized C59N. In the 10–300 K range, T1 of the heterodimer shows a relaxation dominated by the conduction electrons on the nanotubes.

Structural and magnetic properties of small symmetrical and asymmetrical sized fullerene dimers

Materials Research Express

Magnetism in carbon nanostructures is of high scientific interest, which could lead to novel magnetic materials. The magnetic properties of symmetrical and asymmetrical sized small fullerene dimers (C n for n≤50) have been investigated using spin polarized density functional theory. The interaction energies depict that small fullerene cages form stable dimer structures and symmetrical sized fullerene dimers are found more stable than asymmetrical sized dimers. The dimerization of fullerene cages in different modes leads to change in their magnetic properties. The non-magnetic fullerene cages become magnetic after formation of dimer (C 20-C 20 , C 24-C 24 , C 32-C 32 , C 40-C 40 , C 20-C 24 , C 40-C 44 and C 44-C 50), whereas the magnetism of magnetic fullerenes is enhanced or lowered after dimerization (C 28-C 28 C 36-C 36 , C 24-C 28 , C 28-C 32 , C 32-C 36 and C 36-C 40). The individual cages of dimer structures show ferromagnetic interactions amongst them and resultant magnetic moment strongly depends on the type of interconnecting bonds. The magnetism may also be explained based on distortion of carbon cages and change in the density of states (DOS) in dimer configuration. The calculations presented show strong possibility of experimental synthesis of small fullerene based magnetic dimers.

Dynamics of Paramagnetic Metallofullerenes in Carbon Nanotube Peapods

Nano Letters, 2008

We filled SWNTs with the paramagnetic fullerene Sc@C 82 to form peapods. The interfullerene 1D packing distance measured using TEM is d ) 1.1 ( 0.02 nm. The Sc@C 82 in SWNT peapods continuously rotated during the 2 s TEM exposure time, and we did not see the Sc atoms. However, Sc@C 82 metallofullerenes in MWNT peapods have periods of fixed orientation, indicated by the brief observation of Sc atoms. La@C 82 peapods were also prepared and their rotational behavior examined. The interfullerene 1D packing of both La@C 82 and Sc@C 82 peapods is identical and thus independent of the charge transfer state for these paramagnetic fullerenes. The La@C 82 metallofullerenes in the peapods have fixed orientations for extended periods of time, up to 50 s in some cases. The La@C 82 spontaneously rotates rapidly between fixed orientations.

Structures, Interactions, and Ferromagnetism of Fe−Carbon Nanotube Systems

The Journal of Physical Chemistry C, 2008

The structures, interaction, and magnetic properties of Fe atoms with a single-wall carbon nanotube are investigated using Car-Parrinello molecular dynamics. The stability, band gap, Fermi energy, and total magnetic moment of the Fe-adsorbed single-wall carbon nanotube systems are found to depend on the location of the Fe atoms relative to the carbon nanotube surface. The confinement and the curvature of nanotubes have a strong effect on the relative stability of various structures corresponding to different positions of the Fe atom inside and outside carbon nanotubes. The Fe atoms inside a carbon nanotube are found to couple ferromagnetically.

Magnetism of Covalently Functionalized Carbon Nanotubes

2011

We investigate the electronic structure of carbon nanotubes functionalized by adsorbates anchored with single C-C covalent bonds. We find that, despite the particular adsorbate, a spin moment with a universal value of 1.0 muB\mu_BmuB per molecule is induced at low coverage. Therefore, we propose a mechanism of bonding-induced magnetism at the carbon surface. The adsorption of a single molecule creates a dispersionless defect state at the Fermi energy, which is mainly localized in the carbon wall and presents a small contribution from the adsorbate. This universal spin moment is fairly independent of the coverage as long as all the molecules occupy the same graphenic sublattice. The magnetic coupling between adsorbates is also studied and reveals a key dependence on the graphenic sublattice adsorption site.

Electron-state control of carbon nanotubes by space and encapsulated fullerenes

Physical Review B, 2003

We report total-energy electronic structure calculations that provide energetics of encapsulation of various fullerenes in carbon nanotubes and electronic structures of resulting carbon peapods. We find that the electron states of the peapods depend on the space in the nanotubes and that they reflect electron states of the encapsulated fullerenes. The deep energy position of the lowest unoccupied state of fullerenes as well as hybridization between states of the fullerenes and the nearly free-electron states of the nanotubes causes a multicarrier character in the peapods.

Electronic and magnetic properties of iron chains on carbon nanotubes

Microelectronics Journal, 2003

In this work the structural, electronic and magnetic properties of one-dimensional Fe chains interacting with a semiconductor single-wall carbon nanotube are investigated using first-principles spin-polarized calculations. A systematic study of several configurations of a Fe wire interacting with a nanotube both from outside as well as inside is presented, and the resulting equilibrium distances, binding energies and magnetizations are discussed. The most stable configurations are compared with previous results obtained for a single Fe atom interacting with the tube.

Theoretical study of iron-filled carbon nanotubes

Physical Review B, 2006

The structural arrangements and magnetic properties of iron encapsulated in single wall carbon nanotubes ͑SWCNT͒ are investigated. Fe nanowires are of interest because of their potential use in spintronics. They have also been fabricated inside carbon nanotubes, where occasionally exchange bias has also been detected. An additional motivation to study these systems is to contribute to the understanding of how the iron-carbon interaction determines the magnetic ordering. Here we investigate, using ab initio methods, the geometry and magnetic structure of freestanding and encapsulated Fe nanowires, and also the properties of the nanowirenanotube system when defects are present in the single wall carbon nanotube. When the ratio of the nanowire to nanotube diameter is small the system is stable and the spin polarization at the Fermi energy is large, thus making the system potentially interesting for spintronics. When this ratio is close to one the system is less stable and a tendency towards antiferromagnetic ordering is observed.