Goran Karapetrov

Pac-man like nanomagnets could store two bits of information in a single cell

In our most recent work conducted in collaboration with our colleagues at the Institute of Electrical Engineering, Slovak Academy of Sciences, we look at the process of vortex nucleation in nanomagnets. Magnetic vortices are formed in small magnetic structures. The vortices are characterized by a core with specific polarity and the in-plane curl of the moments around the core (vortex chirality). The four-fold degenerate magnetic state of the nanoparticle (two vortex polarities and two vortex chiralities) has a potential to carry two bits of information. The problem has been how to set and read the vortex chirality and polarity independently.

We propose a nanostructure with broken rotational symmetry (resembling the all-popular Pac-man) that could be used as an information storage unit that contains two bits. We show that the vortex polarity and chirality can be set independently by applying in-plane magnetic fields only, which is compatible with the today's hard drive write-head design. The readout is also very convenient since stray fields easily identify both polarity and chirality direction.

This is yet another clear example of how the reduction in size to submicron lengthscale changes completely the magnetic behavior of the system and creates new opportunities to advance the density of the information storage media.