Source: thznetwork.net

An ultrafast spin current triggers the emission of Terahertz-Radiation. Graphics: H. D. Wöhrle/Universität Göttingen

The demands for ever increasing speed of information storage and data processing have triggered an intense search for finding the ultimately fast ways to manipulate spins in a magnetic medium. In this context, the use of femtosecond light pulses¡ªthe fastest man-made event¡ªwith photon energies ranging from X-rays (as used for instance at the HZB femto-slicing facility) to THz spectral range proved to be an indispensable tool in ultrafast spin and magnetization dynamics studies.

In a paper in Nature Nanotechnology, HZB-scientist Ilie Radu and his colleagues from Fritz-Haber-Institut Berlin, Uppsala, Göttingen and Forschungzentrum J¨¹lich demonstrate a simple but very powerful way of manipulating the spins at unprecedented speeds within the so far unexplored THz range (1 THz=10¹² Hz). They use a femtosecond laser pulse to photo-excite the spins from a magnetic material to a non-magnetic one that is chosen to either trap or release the electrons carrying the spins. By this method they are able to generate ultrashort spin currents with tailor-made shapes and durations, which are detected using an ¡®ultrafast amperemeter¡¯ (based on the Inverse Spin Hall Effect) that converts the spin flow into a terahertz electromagnetic pulse.

These findings will possibly allow us to develop and design novel material with tailor-made characteristics, which might boost the magnetic recording rates of the magnetic bits to unprecedented speeds at THz frequencies.

Publication: Terahertz spin current pulses controlled by magnetic heterostructures.