Ultrafast Spin Manipulation at THz frequencies

An ultrafast spin current triggers the emission of Terahertz-Radiation. © 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 – the fastest man-made event - with 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 Jülich demonstrate a simple but very powerful way of manipulating the spins at unprecedented speeds within the so far unexplored THz range (1THz=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. 

I.R.

The work is published in:T. Kampfrath et al. „Terahertz spin current pulses controlled by magnetic heterostructures”, Nature Nanotechnology 2013, doi: http://dx.doi.org/10.1038/NNANO.2013.43.