Magnetic data memories are always based on devices with two stable magnetic states, which can be switched between them. Good candidates for such devices are annular structures made of a permanent-magnetic material with minute diameters of a thousandths of a millimeter. These nanorings may be magnetized clockwise or counterclockwise. However, switching between the two states has so far only succeeded if a complex circular-magnetic field is applied.
Nanoringe can be easily switched
A team of scientists from different research facilities in Germany has shown how it could be easier. If the hole in the ring is not arranged in the middle, but slightly asymmetrical so that the ring is thinner on one side than on the other, then Switching is easy! A magnetic field, which must be stable for only a few billionths of a second, is sufficient to rotate the magnetization clockwise in the counterclockwise direction.
A short-term magnetic field is sufficient
At the Maxymus beamline of BESSY II, the team was able to observe with the help of time-resolved X-ray microscopy how the magnetization develops after the short magnetic field pulse is applied: Thus, the magnetic pulse initially forms two domain walls in the ring. As soon as the external magnetic field is switched off, the domain walls move towards one another very quickly and are destroyed.As a result, the magnetization rotates clockwise into the counter-direction.
Fast process for spintronics
“Our measurements show that the domain walls move an average of 60 meters per second. This is very fast for spintronic applications, “says Dr. Mohamad-Assaad Mawass, first author of the publication in Physical Review Applied. Mawass has already worked on these experiments as part of his doctoral thesis at Johannes Gutenberg University Mainz (group of Prof. Kläui) together with the group around Gisela Schütz from the Max Planck Institute for Intelligent Systems, Stuttgart.Now he was able to continue this research as a postdoc at the X-PEEM beamline at the HZB. “We are convinced that we have found a robust, reliable switching process that is suitable for applications in spintronics, for example for energy-efficient data storage,” says Mawass.