Micromagnetic modelling of ferromagnetic cones

Using micromagnetic modeling, we calculate numerically the magnetization reversal of soft permalloy cones of height and diameter ≤ 100nm. By varying the cone height and the base diameter in steps of 10nm and 5nm, respectively, we map the remanent states systematically. We observe reversal mechanisms with remanent configurations ranging from single domains at small diameters, through buckle states and complex C-states through to vortex states at larger diameters and heights. We present a phase-diagram of the remanent states of magnetization as a function of diameter and height. For the largest cones investigated, we find magnetization configurations in the reversal process which consist of two superimposed vortices with cores pointing in orthogonal directions.