Shape and Proximity Effect of Magnetic Nanoelements Used as Biomolecular Labels for Magnetic Notched Nanowire Biosensors

Three magnetic nanoelements of different shapes and sizes were investigated as potential candidates for biological magnetic labels to be used on a biosensor, which incorporates magnetoresistive nanowires. Circular, square, and triangular nanoelements were positioned at varying distances from a Permalloy, single notched, nanowire to determine how the shape and proximity of the nanoelements affected the domain wall structure of the nanowire. All results were simulated using micro-magnetic simulations by the object oriented micro-magnetic framework. It is shown that both the proximity and the shape of each of the nanoelements produce changes in the domain structure that are specific to the nanoelement and could potentially generate measurable magnetoresistive changes. The 200 nm diameter circularly shaped nanoelement had the greatest proximity effect on the nanowire. It also had a closed, circular domain structure when isolated, which is potentially useful since this is likely to reduce the tendency of biologically labeled material in solution to form agglomerations.