Micromagnetic modelling of ferromagnetic cones

Using micromagnetic modelling, 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 10 and 5 nm, 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.