Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field

TL;DR

This paper demonstrates a method to reliably switch between two 360-degree domain wall vortex states in cobalt nanorings using an azimuthal Oersted field, advancing potential applications in low-power magnetic memory devices.

Contribution

It introduces a controlled switching technique between vortex states in nanorings via current-induced Oersted fields, enabling stable data storage states.

Findings

Successful switching between vortex states using current-induced fields.

Reversible control of domain wall positions in nanorings.

Ability to annihilate domain walls and create vortex states with larger currents.

Abstract

We demonstrate magnetic switching between two $360^\circ$ domain wall vortex states in cobalt nanorings, which are candidate magnetic states for robust and low power MRAM devices. These $360^\circ$ domain wall (DW) or "twisted onion" states can have clockwise or counterclockwise circulation, the two states for data storage. Reliable switching between the states is necessary for any realistic device. We accomplish this switching by applying a circular Oersted field created by passing current through a metal atomic force microscope tip placed at the center of the ring. After initializing in an onion state, we rotate the DWs to one side of the ring by passing a current through the center, and can switch between the two twisted states by reversing the current, causing the DWs to split and meet again on the opposite side of the ring. A larger current will annihilate the DWs and create a perfect vortex state in the rings.