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discovered_02_2013

research// The HZDR Research Magazine WWW.Hzdr.DE 32 33 transmission electron microscope operated there has the capability of differentiating between magnetic directions at a resolution of 20 nanometers, just right for his structures. Sebastian Wintz observed the familiar magnetic vortices in the individual magnetic layers. What was new, however, were vortices he discovered between two magnetic layers – circulating around the intermediate layer. "These are therefore not just two-dimensional, but instead three-dimensional magnetic vortices," explains Wintz the new phenomenon. However, they only occur in certain cases, e.g. when the magnets in the stacked single layers have opposite directions of rotation and are also slightly off-axis. This condition is favored in turn by the very thin intermediate layers, which you can selectively influence. To do this, they are bombarded with high-speed charged particles in the HZDR ion beam center. This results in disordering of the atoms and blurring of the boundaries between the magnetic layers and the non-magnetic intermediate layer. Depending on how strongly the materials are bombarded, the magnets "couple" in the individual layers in a certain way with each other and orient themselves in the desired direction. Stable instead of unstable The magnetic layer system produced by Wintz can also be made into transmitters for electromagnetic waves by applying current. And yet the new three-dimensional magnetic vortices could help antennas remain stable, even at high power: "The magnetization in the core no longer switches back and forth as easily with the new magnetic vortices. The system of layers is therefore probably more suitable for vortex antennas than comparable single layers. Even at high vortex rotational speeds, the magnetic orientation of the vortex core remains unchanged," says Wintz. Transmission frequencies of more than a gigahertz – that corresponds to one billion vortex rotations per second – simultaneously with a high signal quality would be conceivable. Today’s WiFi and cellular networks operate in this frequency region, for example. Until now, the junior scientist’s work has only been basic research. He is continuing at the moment to concentrate on influencing magnetic systems of layers using current or magnetic fields – at higher frequencies than before. He can only hint at more interesting observations thus far. However, this much could be said: these involve not just possible applications for radio antennas, but instead the potential of magnets to process information in very small spatial dimensions, with the help of what are known as "spin" waves. One can count on further exciting and useful phenomena from the world of magnetism. Contact _Institute of Ion Beam Physics und Materials Research at HZDR Sebastian Wintz s.wintz@hzdr.de WRITING WITH ELECTRONS: Physicist Sebastian Wintz at the electron-beam writer, a device used to incorporate ultra-small structures into wafer coats. Photo: Oliver Killig

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