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Forschungszentrum Jülich - Annual Report 2011

CreatingKnowledge Annual Report 2011 | Forschungszentrum Jülich tions on the Jülich supercomputers. “We were certain from the very begin- ning that we had discovered skyrmions, but we could only prove it using com- puter simulations,” says Blügel. According to the computer model, skyrmions occur as a result of a com- plex interaction of three magnetic ef- fects. First of all, there is the conven- tional interaction between the spins located at each of the atoms. The spin, which can be compared to small ele- mentary magnets, is a quantum-me- chanical property of particles. A sec- ond non-linear interaction involving four spins at a time is decisive. The third effect is called the chiral Dzya- loshinskii-Moriya interaction. The com- puter model will help the scientists to selectively influence magnetic struc- tures and surfaces in the future. Spirals as information bits “The magnetic skyrmions that we have discovered behave like particles and they arrange themselves like atoms on a two-dimensional lattice,” says Blügel. Each of the magnetic spirals comprises the spins of a mere fifteen atoms. These fifteen atoms therefore represent an in- formation bit: they can assume a state to which “zero” can be assigned or a state to which “one” can be assigned. In- formation can therefore be expressed as a sequence of “zeros” and “ones”, each comprising fifteen atoms. The magnetic bit as found in hard drives today com- prises around one million atoms. Data storage based on skyrmions would also have another advantage over today’s magnetic storage systems: magnetic information could be written and read-out directly by means of small electric currents. At the moment, an in- formation bit is created on a hard drive using a magnetic field in read-write heads, which requires a current that is Around one million atoms are needed to create a magnetic information bit in today’s hard drives – for data storage based on skyrmions, only fifteen would be needed. one hundred thousand times greater. Skyrmions are therefore very promising candidates for a technology that would allow data to be stored and processed in a highly energy-efficient manner. 31