Magnetic properties of α-Fe and Fe3C nanowires

Controlling the quantity of γ-Fe inside multiwall carbon nano-onions: the key role of sulfur

One of the most interesting structural features of multiwall carbon onions (MWCNOs) and nanotubes (MWCNTs) is the excellent chemical stability, which allows in situ encapsulation of chosen magnetic materials of interest and multifunctional applications. In this letter, we present an innovative chemical vapour synthesis (CVS) approach, in which the inclusion of small quantities of sulfur during the pyrolysis of ferrocene/dichlorobenzene mixtures allows for an important control in the relative abundance of FCC γ-Fe, up to a maximum value of ∼86.5% (structural- and phase-control). The variation in the relative percentage of the encapsulated Fe-based phases was estimated by employing X-ray diffraction (XRD) and Rietveld refinement analyses. The magnetic characterization was achieved by employing superconducting quantum interference device (SQUID) magnetometry, with zero field cooled (ZFC) and field cooled (FC) curves acquired at applied fields of 300 Oe and ∼50 000 Oe.

Magnetization Dynamics of an Individual Single-Crystalline Fe-Filled Carbon Nanotube

The magnetization dynamics of individual Fe-filled multiwall carbon-nanotubes (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 carbon nanotubes as novel monopole-like sensors for quantitative magnetic force microscopy

We present a novel ultrahigh stability sensor for quantitative magnetic force microscopy (MFM) based on an iron filled carbon nanotube. In contrast to the complex magnetic structure of conventional MFM probes, this sensor constitutes a nanomagnet with defined properties. The long iron nanowire can be regarded as an extended dipole of which only the monopole close to the sample surface is involved in the imaging process. We demonstrate its potential for high resolution imaging. Moreover, we present an easy routine to determine its monopole moment and prove that this calibration, unlike other approaches, is universally applicable. For the first time this enables straightforward quantitative MFM measurements.

Carbon Nanotubes Filled with Ferromagnetic Materials

Carbon nanotubes (CNT) filled with ferromagnetic metals like iron, cobalt or nickel are new and very interesting nanostructured materials with a number of unique properties. In this paper we give an overview about different chemical vapor deposition (CVD) methods for their synthesis and discuss the influence of selected growth parameters. In addition we evaluate possible growth mechanisms involved in their formation. Moreover we show their identified structural and magnetic properties. On the basis of these properties we present different application possibilities. Some selected examples reveal the high potential of these materials in the field of medicine and nanotechnology.