Control of vortex chirality and polarity in magnetic nanodots with broken rotational symmetry

We explore size-dependent magnetic states of sub-100-nm Permalloy nanomagnets. The geometry is suitable for independent setting and readout of vortex polarity and chirality by applying in-plane magnetic fields only. Micromagnetic calculations show that in "Pac-Man"-like magnetic nanodots the relaxation channels to specific chirality and polarity states from uniform magnetization state are deterministic and are not influenced by the presence of moderate out-of-plane fields. The particular geometry opens a straight channel for magnetization relaxation toward a stable closure-domain vortex state with specific chirality and polarity. We show that in these nanomagnets the write process is simple and the signal is easily readable.