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PGI-1 Seminar: Dr. Tobias Kampfrath

Probing and controlling spin dynamics with terahertz pulses

05 Aug 2015 11:30
PGI Lecture Hall

Fritz-Haber Institute, Berlin


Terahertz (THz) electromagnetic radiation is located in the gap separating the realms of electronics (<1 THz) and optics (>30 THz). Sub-picosecond THz pulses are capable of probing and even controlling numerous low-energy excitations such as phonons, excitons or Cooper pairs. Here, we consider experiments showing that THz radiation is also a very useful and versatile tool in the field of spin-based electronics (spintronics).

First, we use intense THz pulses to manipulate the magnetic order of solids. This goal is achieved directly by driving and stopping magnons in antiferromagnetic NiO with THz magnetic fields. As a more indirect path toward spin control, we excite optical phonons in the model ferrimagnet Y3Fe5O12 (YIG) and observe a magnetization quenching on a surprisingly fast time scale of 1 ps. This result provides new insights into spin-lattice coupling of dielectrics and helps us reveal the underlying microscopic interactions.

Second, to address spin transport, a femtosecond laser pulse is used to inject spin-polarized electrons from a ferromagnetic into a nonmagnetic metal film. The resulting ultrafast spin current is detected through the inverse spin Hall effect that converts the spin Flow into a measurable THz pulse. Choosing nonmagnetic layers with different electron mobility allows one to tailor the temporal shape of the spin current and to design novel emitters of THz radiation.


Prof. Dr. Yuriy Mokrousov
Phone: +49 2461 61-4434