The key here is the way the nitrogen ions migrate from the material. Their movement begins at the bottom of the nanodot (closest to the electrode) and proceeds upward, creating a growing ferromagnetic layer from the bottom up.
As this ferromagnetic layer thickens, the magnetic moments spontaneously arrange into a vortex state, consisting of magnetic moments rotating around a central core. This configuration, which the researchers named a vortion, allows for precise, energy-efficient control of magnetic properties.
Precise control over magnetic properties
The magnetic properties of a vortion aren’t fixed. The longer a voltage is applied, the more ions move out, and the thicker the magnetic layer becomes.
To test its magnetic properties after formation, the researchers apply external magnetic fields of varying strengths. They discovered that voltage application time creates measurable, distinct differences in magnetic properties.