Enhanced magnetic coercivities in Fe nanowires

We describe a way of generating films (< 2 mm(2); < 40 mu m thick) of align ed Fe-filled carbon nanotubes. These Fe nanowires are usually composed of s ingle Fe crystals, and have dimensions from 5-40 nm outer diameter and < 10 mu m in length. The carbon tubes, which coat the wires, have external diam eters of similar to 20-70 nm and are < 40 mu m in length. High-resolution e lectron energy loss spectroscopy, x-ray powder diffraction, and elemental m apping of the tubular structures reveal only characteristic metallic signal s and the effective absence of oxygen (or any other nonmetallic element) wi thin the wires. The material exhibits coercivities in the 430-1070 Oe range , i.e., greater than those reported for Ni and Co nanowires. (C) 1999 Ameri can Institute of Physics. [S0003-6951(99)00247-8].