Control of vortex chirality in Ni80Fe20 dots using dipole coupled nanomagnets

A magnetic vortex is an in-plane circulation of magnetization around a nanometer-scale central core with out-of-plane magnetization pointing either up or down. Circulation of the magnetization, known as vortex chirality (VC), also has two possible states depending on the sense of circulation: clockwise (CW) and counterclockwise (CCW). Its potential for storing two units of information in a single cell lies in the fact that the polarities of the core and the VC states can be controlled independently. However efficient and reliable switching of the core and chirality pose significant technological challenges. Here, we report a simple in-plane field driven control of vortex chirality in Ni₈₀Fe₂₀ circular disks using dipole-coupled rhomboid nanomagnets (R-NMs) . This method does not alter the geometry of the circular disk to control the chirality and can be fabricated using a single step lithographic process . The strategy for VC control depends on the magnetostatic interactions between the biasing R-NMs and the central dot which lead to anti-parallel nearest-neighbor orientation at remanence. In-field magnetic force microscopy (MFM) technique was used to probe the chirality of the vortex. Experimental results were validated with micromagnetic simulations using OOMMF software with standard parameters for Ni₈₀Fe₂₀.