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A new simple method permits the growth of vertically aligned iron oxide haematite nanowires with potential applications in magnetic storage media

Credit: © 2006 AIP

Vertically aligned, one-dimensional nanowires synthesized from alpha-Fe₂O₃ (haematite) have unique physical properties not observed in the bulk form and can function as gas sensors, transistors and field emitters. However, in spite of these important industrial applications, there is still not a simple method for producing high-quality, vertically aligned alpha-Fe₂O₃ nanowires.

Now, Jeunghee Park and colleagues from Korea University and the Korea Basic Science Institute have synthesized large areas of vertically aligned alpha-Fe₂O₃ nanowires by thermal oxidation of iron foil substrates at 800 °C. The nanowires were grown using gallium and tin as catalysts. The resulting rhombohedral nanowires were 15 µm long after only 30 minutes of growth and had widths of 100–300 nm and 50 nm at the base and tip, respectively.

The nanowires are weakly ferromagnetic at room temperature and antiferromagnetic at cryogenic temperatures. Surprisingly, they magnetize most easily perpendicular to the long growth axis, in contrast to Fe and Co nanowires, which magnetize parallel to the growth direction. The perpendicular magnetic anisotropy, which remains stable to a relatively low temperature compared to bulk alpha-Fe₂O₃, makes these nanowires good candidates for high-density magnetic storage media.