Controlled magnetization reversal in patterned Co nanostructures

Abstract

We have successfully demonstrated the construction of patterned magnetic nanostructures down to 50 nm dimensions using electron-beam lithography. Two types of patterned structures have been fabricated for this work: nanostructured arrays consisting of isolated identical elements and nanostructured chains of alternating elements with different widths. Small patterned arrays (∼200 μm×200 μm) have been characterized using a variable temperature (5 to 325 K) focused magneto-optic Kerr effect (MOKE) measurement system. The switching field of the isolated element arrays is found to be inversely proportional to the element width. However, as the elements of two different widths are connected to form a chain, magnetization reversal is essentially controlled by the wider constituent, indicating that the switching of chains starts in the wider elements. Domain walls in these wide elements then propagate through the narrower components, requiring a lower field than domain nucleation in the narrow elements. Magnetic force microscopy (MFM) images show that in the virgin state the narrower elements are domain wall free but complex domain patterns exist in the wider elements. Both field-dependent MFM imaging and micromagnetic simulations agree very well with the MOKE measurements.