Magnetoresistive detection of single magnetic vortices

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been exploited in spin-torque-driven nano-oscillators [A. Wachowiak et al., Science (2002)]. The fundamental frequency is determined by the saturation magnetisation, as well as the geometrical confinement of the magnetisation e.g. the diameter and height of a magnetic disk. The objective of this study is to design magnetic discs, contact them with electrical leads and probe the dynamics of the vortex structures using magnetoresistive detection. By varying the thickness and dimensions of the disk, requirements for the magnetic vortex as a ground state will be determined. The electrical resistance of a single disc is expected to change based on the relative angle between the magnetisation direction and the applied current (the anisotropic magnetoresistance (AMR) effect) [S. Kasai et al, PRL 97, 107204 (2006)]. Using the AMR as a detection technique we will determine if electrical detection of dynamics is feasible in this geometry and its associated limits.