Self-assembled and patterned Fe and Fe3O4 dots on III-V semiconductors

In this article we reviewed the experimental results of self-assembled and patterned Fe and Fe3O4 dots on GaAs(100) and InAs(100) surfaces. Superparamagnetic nanoclusters were formed during the Molecular Beam Epitaxy (MBE) growth of the Fe on both GaAs(100) and InAs(100) substrates within 2.5 to 4.8 ML coverage. STM, MOKE and XMCD measurements were performed to characterize the structural and magnetic properties of these nanoclusters. These nanoclusters exhibit strong uniaxial anisotropy of the order of 6.0 X 105 erg/cm3. Magnetic domain structures and coersivities of the epitaxial Fe films grown on GaAs(100) and patterned into arrays of circular dot were also investigated. MOKE and MFM studies revealed that the 1 µm diameter single domain dot arrays showed direct evidence of strong interdot dipolar coupling when the separation is reduced to 0.1 µm. The coercivities of the dots were also observed to be dependent on the separation and size of the dots indicating that interdot dipolar coupling affects the magnetization processes in these dots. Fe3O4 films grown on deformed GaAs(100) substrate formed nanostripes following the topography of the substrate. MOKE measurements showed that these nanostipes have uniaxial magnetic anisotropy with easy axis perpendicular to the length of the nanostripes. This suggests that the magnto-elastic coupling plays more dominant role than that of the shape anisotropy in determining the magnetic properties of these nanostripes.