OPTIMAS researchers succeed in understanding a novel read-write concept for computers

Heating of a magnet, e.g. with the flame of a Bunsen burner, weakens its attraction on an iron nail. Expressed in the language of physics one says that the magnetization of the magnet has been reduced or shortly spoken: it has been demagnetized. Since the beginning of the last century it is known that the magnetization of a magnet is carried by the so called spins. Spins can be visualized by tiny arrows which perform a rotational motion around their own axis very similar to a gyroscope. Heating destroys the originally uniform orientation of the spins and drives them into disorder.

In Germany and The Netherlands forefront research is concentrated on the field of ultrafast demagnetization. Researchers intensively discuss the question how fast a spin can change its direction and which are the predominant microscopic interactions behind the spin flip mechanism. The group of Prof. Dr. Martin Aeschlimann from the University of Kaiserslautern has approached this fundamental challenge in close cooperation with researchers from the University of Eindhoven and with theoretical support by the Max-Planck Institute of Metal Research in Stuttgart. As an ultimate goal a model was developed that is able to describe the rich variety of experimental findings and leads to a deep understanding of the microscopic basis of the detailed motion of spins.

The corresponding intricate physical experiment can be well compared with the effect of a Bunsen burner on a magnet as illustrated in the introduction. However, instead of the Bunsen burner a special laser is applied as investigation tool. It generates extremely short - denoted as ultrashort - packages of light which are, in comparison to the shortest feasible electronic pulses, a factor of 100 faster. The light pulses of the laser hit the magnet

which in this case consists of a magnetic thin film with a thickness of ten nanometers. The implanted energy leads to a sudden heating up of the system of spins and induces its disorder. As a consequence a demagnetization develops on an ultrashort timescale of around 100 fs. Keep in mind that the ratio of 100 fs over one second behaves like half a day to the age of our universe or like a millisecond to 300 years. Regarding the tremendous velocity of this all optical strategy it outclasses the contemporary standard technology. A forceful application of this novel concept promises to pave the way for a revolutionary read-write concept in computers.

In a future project also the lateral dimension of the thin magnetic film shall shrink to nanometer size by preparation of so called nanodots. By means of an intelligent tailoring of the physical properties of the laser pulse the researchers hope even to demagnetize or switch one single nanodot - this would mean that one could write a nanometer sized bit ultrafast.

The original article has been published in the trade magazine Nature Materials: dx.doi.org/10.1038/NMAT2593

Press release by the University of Kaiserslautern from Dec. 14, 2009