Magnetic properties of aligned Fe-filled carbon nanotubes

Mühl, Thomas; Elefant, D.; Graff, Andreas; Kozhuharova, R.; Leonhardt, A.; Mönch, Ingolf; Ritschel, M.; Simon, Pascal; Groudeva‐Zotova, S.; Schneider, Claus M.

doi:10.1063/1.1557824

Cited by 110 publications

(32 citation statements)

References 16 publications

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“…Additionally, encapsulation may give rise to new magnetic properties not present in conventional magnetic nanowires 25 and even change the mechanical stability of the nanotubes 26 . These include, for example, hysteresis loop shifts due to exchange bias 27,28 , changes in the complex permittivity and permeability 29 , increased coercitivity and Barkhausen jumps 30 , magnetic anisotropy 31 , size and number-dependent interactions between catalyst particles 32 and many other magnetic phenomena. Other fascinating properties include the disappearance of magnetism in small clusters of Ni atoms 34 or the antiferromagnetic behavior shown by iron 35,36 .…”

Section: Introductionmentioning

confidence: 99%

Strongly correlated electron physics in nanotube-encapsulated metallocene chains

2006

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The structural, electronic and transport properties of metallocene molecules (MCp2) and isolated or nanotubeencapsulated metallocene chains are studied by using a combination of density functional theory and nonequilibrium Green's functions. The analysis first discusses the whole series of isolated MCp2 molecules, where M = V, Cr, Mn, Fe, Co, Ni, Ru, and Os. The series presents a rich range of electronic and magnetic behaviors due to the interplay between the crystal field interaction and Hund's rules, as the occupation of the d shell increases. The article then shows how many of these interesting properties can also be seen when MCp2 molecules are linked together to form periodic chains. Interestingly, a large portion of these chains display metallic, and eventually magnetic, behavior. These properties may render these systems as useful tools for spintronics applications but this is hindered by the lack of mechanical stability of the chains. It is finally argued that encapsulation of the chains inside carbon nanotubes, that is exothermic for radii larger than 4.5Å, provides the missing mechanical stability and electrical isolation. The structural stability, charge transfer, magnetic and electronic behavior of the ensuing chains, as well as the modification of the electrostatic potential in the nanotube wall produced by the metallocenes are thoroughly discussed. We argue that the full devices can be characterized by two doped, strongly correlated Hubbard models whose mutual hybridization is almost negligible. The charge transferred from the chains produces a strong modification of the electrostatic potential in the nanotube walls, which is amplified in case of semiconducting and endothermic nanotubes. The transport properties of isolated metallocenes between semi-infinite nanotubes are also analyzed and shown to lead to important changes in the transmission coefficients of clean nanotubes for high energies.

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Section: Introductionmentioning

confidence: 99%

Strongly correlated electron physics in nanotube-encapsulated metallocene chains

2006

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“…Therefor, the nanocomposite shows weaker magnetic property when the external field along tube direction.Generally, this factor was neglected when analyzing the magnetic anisotropy of Fe or Fe 3 C filled CNTs [26][27]. Secondly, large shape anisotropy [28] and magnetocrystalline anisotropy contribution [29] should be responsible for the magnetic anisotropy of the CNT/ Fe 3 C nanocomposites.…”

Section: Resultsmentioning

confidence: 99%

Patterned growth of vertically aligned carbon nanotube arrays using colloidal lithography and plasma enhanced chemical vapor deposition

Man

Chen

Zhang

et al. 2015

Journal of Alloys and Compounds

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“…5 Because coercivity is a key criterion in evaluating a ferromagnetic material, 6 a precise and wide-range control of the coercivity of Fe-filled CNTs is of great importance from the viewpoint of fundamental research and also for practical applications. 7 Coercivities ranging from ϳ300 to ϳ600 Oe have recently been reported for Fe-filled CNTs, [8][9][10][11] which highlight the need to find a method to tune the coercivity of Fe-filled CNTs. This coercivity originates from the encapsulated Fe nanoparticles ͑Fe-NPs͒ because the CNTs are diamagnetic.…”

Section: Introductionmentioning

confidence: 98%

Tuning the coercivity of Fe-filled carbon-nanotube arrays by changing the shape anisotropy of the encapsulated Fe nanoparticles

Shi

Cong

2008

Journal of Applied Physics

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To tune the coercivity of Fe-filled carbon-nanotube (CNT) arrays, the shape anisotropy of encapsulated Fe nanoparticles (Fe-NPs) was investigated. Four Fe-filled CNT-array samples with different Fe-NP aspect ratios were prepared by catalytic pyrolysis of acetylene using ferrocene as catalyst. The coercivity of the Fe-filled CNT arrays increased from ∼300 to ∼800 Oe at room temperature when the mean aspect ratio of the encapsulated Fe-NPs changed from 1.6 to 6.0. This clear dependence of the coercivity of the Fe-filled CNT arrays on the aspect ratio of the Fe-NPs might be interpreted in terms of the Stoner–Wohlfarth model. This result indicates that changing the shape anisotropy of the encapsulated Fe-NPs is an effective method to tune the coercivity of the Fe-filled CNTs.

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Magnetic properties of aligned Fe-filled carbon nanotubes

Cited by 110 publications

References 16 publications

Strongly correlated electron physics in nanotube-encapsulated metallocene chains

Strongly correlated electron physics in nanotube-encapsulated metallocene chains

Patterned growth of vertically aligned carbon nanotube arrays using colloidal lithography and plasma enhanced chemical vapor deposition

Tuning the coercivity of Fe-filled carbon-nanotube arrays by changing the shape anisotropy of the encapsulated Fe nanoparticles

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