Magnetostatic interaction between magnetic domain walls in dual Co rings

• Closely placed dual Co rings were fabricated by e-beam lithography.
• Magnetic Force microscope (MFM) images show strong and weak domain wall (DW) interaction depending on the angle between the coupling axis and the field direction, and the spacing between rings.
• Surface magnetic charge and volume magnetic charge attractions are suitable for understating of strong and weak DW interaction, respectively.

Magnetostatic interaction of magnetic domain walls (DWs) is investigated by using magnetic force microscopy (MFM) at the remanent state in closely placed Co dual rings. The Co dual rings are 10 and 20 nm in thickness and the spacing between them is varied. In an array of dual rings varying in steps of 10° against the direction of an applied field, the angular dependence of DW interaction shows an obvious change from coupling to decoupling of the DWs in the MFM measurements. It is found that the strong interaction between DWs at smaller angles and smaller spacing is owed to the surface magnetic charge attraction. On the other hand, monopole-like magnetic charge attraction is related with weak DW interaction at higher angles and a larger spacing. In addition, the dependence of the Co thickness on the magnetostatic DW interaction can be explained by the volume magnetic effects.