Magnetic properties of α-Fe and Fe₃C nanowires

Abstract

The magnetic properties of single domain α-Fe and Fe3C nanowires encapsulated within Multi Walled Carbon Nanotubes (MWNT) are investigated with a Magnetic Force Microscope (MFM). The wires are formed during the Chemical Vapour Deposition growth process, partially filling the hollow center of the MWNTs. The wires have a diameter variation of 10-60nm and can be several μm long. The phase and crystal orientation of the filling relative to the long tube axis are probed by Transmission Electron Microscopy. The remanent magnetization states of the wires are investigated by MFM imaging. The α-Fe wires show shape dominated magnetization along the tube axis, whereas the FesC wires show a perpendicular magnetization imposed by magneto-crystalline anisotropy. Switching fields of α-Fe nanowires are determined by the application of an in-situ magnetic field, revealing a tip triggered magnetization reversal by localized nucleation.