Magnetic vortex core reversal by excitation with short bursts of an alternating field

Magnetism with a twist Thin films of ferromagnetic materials patterned into tiny squares or disks can support vortex states in which magnetization forms closed loops within the plane of the structure. These vortices have the potential for use in magnetic data storage, if a controllable means of switching them can be found. Towards the core of the vortex, the magnetization turns up or down (out of the plane), giving the vortex core a net polarization. Excite the vortex, and the structure gyrates in the plane in a direction determined by the polarization of the vortex core. Now Van Waeyenberge et al. show that application of small bursts of an oscillating magnetic field can controllably reverse the direction of gyration — and hence switch the direction of out-of-plane core polarization. Add this switch mechanism to the high stability of these vortex structures, and they start to look promising as memory elements of the future.