Magnetic Properties of 1D Iron–Sulfur Compounds Formed Inside Single‐Walled Carbon Nanotubes (original) (raw)
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Anchoring of Rare-Earth-Based Single-Molecule Magnets on Single-Walled Carbon Nanotubes
Journal of the American Chemical Society, 2009
A new heteroleptic bis(phthalocyaninato) terbium(III) complex 1, bearing a pyrenyl group, exhibits temperature and frequency dependence of ac magnetic susceptibility, typical of single-molecule magnets. The complex was successfully attached to single-walled carbon nanotubes (SWNTs) using π-π interactions, yielding a 1-SWNT conjugate. The supramolecular grafting of 1 to SWNTs was proven qualitatively and quantitatively by high-resolution transmission electron microscopy, emission spectroscopy, and atomic force spectroscopy. Giving a clear magnetic fingerprint, the anisotropy energy barrier and the magnetic relaxation time of the 1-SWNT conjugate are both increased in comparison with the pure crystalline compound 1, likely due to the suppression of intermolecular interactions. The obtained results propose the 1-SWNT conjugate as a promising constituent unit in magnetic single-molecule measurements using molecular spintronics devices.
Magnetization Dynamics of an Individual Single‐Crystalline Fe‐Filled Carbon Nanotube
Small, 2019
motivated by a broad range of applications for magnetoresistive devices, optical meta-materials, cell-DNA separators, drug delivery vectors, [7,8] and wave based information transport. [9] Both, the high stability of their magnetic equilibrium state against external perturbations, as well as their robust domain walls, which propagate with velocities faster than the spin wave phase velocity, promote them as appealing candidates for racetrack memory devices and for information transport and processing using spin waves in magnonic applications. Various bottom-up synthesis routes for the preparation of magnetic nanowires exist; including for example electrodeposition based on porous membrane templates [1] and pyrolysis of metal-organic precursors. In particular the pyrolysis of ferrocene allows for the formation of iron-filled carbon nanotubes (FeCNT), i.e., multiwall carbon nanotubes, which contain single-phase single-crystalline iron nanowires, [10-14] where the body-centered cubic iron phase dominates. Furthermore, iron nanowires with various crystal orientations can be found with no prevalent orientation. [13] The diameters of the carbon nanotubes and the embedded iron nanowires are in the range of 30-100 and 10-40 nm, respectively. [13] The magnetization dynamics of individual Fe-filled multiwall carbonnanotubes (FeCNT), grown by chemical vapor deposition, are investigated by microresonator ferromagnetic resonance (FMR) and Brillouin light scattering (BLS) microscopy and corroborated by micromagnetic simulations. Currently, only static magnetometry measurements are available. They suggest that the FeCNTs consist of a single-crystalline Fe nanowire throughout the length. The number and structure of the FMR lines and the abrupt decay of the spin-wave transport seen in BLS indicate, however, that the Fe filling is not a single straight piece along the length. Therefore, a stepwise cutting procedure is applied in order to investigate the evolution of the ferromagnetic resonance lines as a function of the nanowire length. The results show that the FeCNT is indeed not homogeneous along the full length but is built from 300 to 400 nm long single-crystalline segments. These segments consist of magnetically high quality Fe nanowires with almost the bulk values of Fe and with a similar small damping in relation to thin films, promoting FeCNTs as appealing candidates for spin-wave transport in magnonic applications.
Iron filled single-wall carbon nanotubes – A novel ferromagnetic medium
Chemical Physics Letters, 2006
In our study we use a highly efficient and simple methodology based on wet chemistry to fill single-wall carbon nanotubes (SWCNTs) with iron, and thus create quantum wires in a bulk. The research shown is unique in that it is the first experimental single-wall carbon nanotubes that have iron continuously within their core for extended length scale. The resulting Fe-filled SWCNTs show ferromagnetic behavior even at room temperature, despite the very small diameter. The intercalation of metals within single-wall carbon nanotube structures is a significant step towards the realization of the potential applications using these materials.
Journal of Nanoparticle Research, 2013
Magnetism of supramolecular assemblies of single-walled carbon nanotubes (SWCNTS) with a magnetic dinuclear molecule is investigated. Raman, optical absorption and confocal fluorescence images are used to probe the interaction of the dinuclear compound and the SWCNT. The supramolecular assembly shows antiferromagnetism, on the contrary to the case when strong electronic doping of the SWCNT occurs, yielding a spin-glass system, and contrary to the case of the dinuclear molecular crystal, which is ferromagnetic. The SWCNT imposes the antiferromagnetic order to the dinuclear molecule, corroborating recent findings that antiferromagnetism is present in pure SWCNTs. Two theoretical models are used to fit the data, both yielding good fitting results. The nanoparticle size range is around 2-10 nm.
Advanced Materials, 2007
The determination of the magnetic properties of molecular magnets in environments similar to those used in spintronic devices is fundamental for the development of applications. Single-molecule magnets (SMMs) are molecular cluster systems that display magnetic hysteresis of dynamical origin at low temperature. As they behave like perfectly monodisperse nanomagnets and show clear macroscopic quantum effects in their magnetic properties, they are extremely appealing candidates for the forthcoming generation of molecular devices: they have been proposed as efficient systems for quantum computation, ultra-high-density magnetic recording media, and molecular spintronic systems. These attractive possibilities have stimulated the creativity of chemists and materials scientists in developing several different ways of organizing such systems into addressable nanostructured materials. In particular inclusion into Langmuir-Blodgett (LB) films, [9] mesoporous silica, polymeric matrices, and ultrathin films [12] have been devised and studied. The most appealing approaches, both from the applicative and speculative points of view, are the functionalization and binding of such clusters on conducting surfaces as well as their incorporation into break-junctions, where a single molecule is directly accessible. These results have led to the creation of the first SMM-based molecular spintronic devices, in which the electronic transport properties are modulated by the magnetic state of a single SMM cluster. The considerable difficulties linked to the interpretation of such results have recently stimulated much theoretical work, and a number of predictions have been made. Both topological and quantum tunneling effects on the transport in the Kondo regime have been predicted, and several peculiar fingerprints of the SMM behavior should be apparent in transport measurements. Interesting effects are also predicted when addressing a SMM on a surface with a tunneling current. Although the influence of the surroundings on the magnetic properties of SMMs has been pointed out in several theoretical and experimental works, our understanding of SMM behavior almost totally relies on measurements performed on crystalline samples. Magnetic measurements on SMMs that lie in environments similar to those of spintronic devices have not been reported up to now, mainly because of the very high sensitivity required. In this Communication we try to fill this void by using high-sensitivity instrumentation, based on magneto-optical (MO) techniques on a variety of materials.
Magnetic properties of Fe 3 C ferromagnetic nanoparticles encapsulated in carbon nanotubes
Physics of The Solid State, 2007
The low-temperature dependences of magnetic characteristics (namely, the coercive force H c , the remanent magnetization M r , local magnetic anisotropy fields H a, and the saturation magnetization M s ) determined from the irreversible and reversible parts of the magnetization curves for Fe3C ferromagnetic nanoparticles encapsulated in carbon nanotubes are investigated experimentally. The behavior of the temperature dependences of the coercive force H c (T) and the remanent magnetization M r (T) indicates a single-domain structure of the particles under study and makes it possible to estimate their blocking temperature T B = 420–450 K. It is found that the saturation magnetization M s and the local magnetic anisotropy field H a vary with temperature as ∼T 5/2.
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.
Physics of the Solid State, 2009
Methods have been proposed and tested for analyzing local magnetic parameters in a system of single domain ferromagnetic nanoparticles using their magnetization curves. The magnetic inhomogeneity in ensembles of Fe 3 C nanoparticles encapsulated in carbon nanotubes has been investigated. It has been established that the Fe 3 C nanoparticles encapsulated in carbon nanotubes are characterized by two modal distribution functions of the local magnetic anisotropy energy. The particle distribution over the blocking temperature is reconstructed from the experimental temperature dependence of the coercive force. The allowance made for the inhomogeneity of the local magnetic parameters of the Fe 3 C nanoparticles, which were studied by the proposed methods, explains the discrepancy between the magnetic anisotropy energy determined by the method of the magnetization approaching saturation and the magnetic anisotropy energy estimated from the coercive force of single domain nanoparticles.