Three magnetic states for each hole
Nanometer-scale magnetic perforated grids could create new possibilities for Computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in order to program its magnetic properties. His colleagues from the National University in Singapore produced the grid using a photolithographic process similar to that currently used in chip manufacture. Approximately 250 nanometers sized holes, so-called antidots, were created at regular intervals – with interspaces of only 150 nanometers – in the cobalt layer. In order to be able to stably program it, the Singapore experts followed the Dresden design, which specified a metal layer thickness of approximately 50 nanometers.
At these dimensions the cobalt antidot grid displayed interesting properties: Dr. Bali's team discovered that with the aid of an externally applied magnetic field three distinct magnetic states around each hole could be configured. The scientists called these states "G", "C" and "Q". Dr. Bali: "Antidots are now in the international research spotlight. By optimizing the antidot geometry we were able to show that the spins, or the magnetic moments of the electrons, could be reliably programmed around the holes."
Building blocks for future logic
Since the individually programmable holes are situated in a magnetic metal layer, the grid geometry has potential use in computers that would work with spin-waves instead of electric current. "Spin-waves are similar to the so-called Mexican waves you see in a football stadium. The wave propagates through the stadium, but the individual fans, in our case the electrons, stay seated", explains Dr. Bali. Logic chips utilizing such spin-waves would use far less power than today's processors, because no electrical current is involved.
Many magnetic states can be realized in the perforated grid so that the spin-waves can, for example, be assigned specific directions. This could allow for a higher processing speed in future logic chips. "Our perforated grids could also operate as components for future circuits working with spin-waves", estimates Dr. Bali. Doctoral candidate, Tobias Schneider, is now investigating the dynamics developed by the spin-waves in such perforated grids. Among other aspects he is participating in the development of special computer programs making possible the complex calculation of the magnetic states in perforated grids.