Tailoring the magnetisation dynamics of thin films

Florian M. Römer, Duisburg-Essen, AG Farle, Duisburg, Germany

The damping of any magnetization dynamics is one of the most important properties for the speed of switching magnetic information. Neither the lowest nor the highest damping is useful for every application, but the chance to set it to the desired value is important.

There are intrinsic and extrinsic damping mechanisms, namely the gilbert damping and spin pumping for example, where a precessing magnetization creates a spin current (meaning a spinpolarized current with no net charge transfer). Separating the influence of spin pumping and Gilbert damping is yet not fully done, but can be performed by in situ multifrequency ferromagnetic resonance, as proposed here.

For application, engineers often wish to stick to common materials and only add something additional. Spin pumping is one chance to change the damping of a given material by outer parameters like capping material. A damping, tunable for use as a switch, would be interesting for magnon transistors and the spin laser data transmission.

Using semiconducting substrates, one could change the spin pumping by changing the conductivity using optically excited electrons. Even non-polarized light will have an influence on the spin pumping, but circular polarized light giving spin dependent excitations would be of scientific interest even more: it may increase and decrease the damping depending on helicity. Ideas for those experiments are proposed here.

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