Control of vortex chirality in bi-component magnetic nanodisks

In the last decade, special attention has been paid to the nucleation and control of the vortex state in magnetic nanostructures, for possible applications in nonvolatile magnetic random access memories and logic networks. Here, we study bicomponent magnetic nanodisks, in both single and 2D array arrangements, as potential storage systems where the information unit is represented by vortex chirality (magnetization rotational direction). We mainly focus on 300 nm diameter disks made of a permalloy lens and an iron crescent, with variable locations of the permalloy-iron interface. Through an extensive micromagnetic modeling analysis, we demonstrate the possibility of tuning, via the application of a magnetic field parallel to the interface, the nucleation of the vortex (always occurring in the permalloy region), its motion up to the expulsion site, and its chirality. Moreover, we find that the vortex stability is preserved over a wide field range also for strongly packed disks, due to the reduced effects of interdisk magnetostatic coupling. The main features of the magnetization reversal mechanism are preserved by reducing the disk diameter up to about 60 nm, making possible their exploitation in concept devices for magnetic encoding and logic computation.