The best-known memory device is the magnetic hard drive and here conventional magnetic fields are used to excite spin dynamics and manipulate magnetization as necessary for switching of magnetic bits. While this approach is now reasonably well understood and widely employed, it is an energy-hungry process leading to large power dissipation. Furthermore it entails limitations for the speed of magnetic switching as intrinsically the spin dynamics is limited by the precession frequency corresponding to the magnetic field.
Novel low power storage-class memory devices have been proposed, where switching by alternative means, such as spin-polarized currents is used  and for this we develop new highly spin-polarized materials . We study the rich physics of the interaction between spin currents, photons and the magnetization , and we have used spin-polarized charge carriers and photons to excite spin dynamics and manipulate the magnetization on ultrafast timescales .
Finally using alternative concepts with perpendicular excitation  and using skyrmions [6,7] might open novel avenues to ultra-low power switching of magnetization with THz read-out .
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 J.-S. Kim et al., Nature Comm. 5, 3429 (2014).
 F: Buttner et al., Nature Phys. 11, 225 (2015).
 S. Woo et al., arxiv:1502.07376
 Z. Jin et al., Nature Phys. (advance online publication 2015) doi:10.1038/nphys3384
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