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Foeschungszentrum Jülich - Research in Jülich 1_2013

1|2013 Research in Jülich NEWS IN BRIEF ‘Hot’ Spins for Efficient Storage Spin currents excited by laser pulses (red arrows) can increase the magnetization of layers. Like Honey on Toast T hread-like molecules, such as DNA, form spirals when they flow through microscopically small channels. Jülich scientists have provided explana- tions for the forces that bring about this deformation in the journal Physical Re- view Letters. Understanding the flow be- haviour of such molecules is important for the development of (disposable) medi- cal tests, for example, where tiny amounts of blood or other fluids flow through microscopic channels. The researchers had simulated the movement of the chain-like molecules through a tube with a varying diameter. Whereas the thread molecules were elongated while traversing the narrow segments, they curled when the tube be- came wider and eventually formed a spi- ral. The reason is the lower velocity of flow in the wider segments of the tube. When they reach these segments, the ‘leading’ part of the molecule chain slows down while the rest follows at un- abated speed, causing the chain to roll Thread-like molecules also form spirals when they flow. 5 up in the process. The shape of the emerging coil depends on several factors, including the flexi- bility of the long-chain molecules, their flow velocity, and the ratio of the different tube diameters. A similar phenomenon of curling can also be observed in daily life: when hon- ey flows from the spoon onto your breakfast toast. :: An international team of researchers including scientists from Forschungs- zentrum Jülich have discovered a new physical effect in a system of magnet- ic layers. This effect, in which ‘hot’ spin currents are produced, could open up new avenues for computer technology. The magnetic properties of materials are based on electron spins. In the future, these spins will be increasingly used to magnetically store information. The new effect could be utilized for a new generation of ultrafast, energy-efficient, high- capacity computer storage. The re- searchers found that short laser puls- es are not only able to reduce the magnetization of layer, but also to in- crease it. Which of the two effects will occur depends on whether the orientation of the superimposed mag- netic layers was initially parallel or an- tiparallel. The laser pulses make ‘hot’ spins move extremely fast, thus caus- ing spin currents. The researchers are now searching for materials that in- duce stronger spin currents and for possibilities of selectively channelling these spin currents.

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