Abstract-Terahertz spin current pulses controlled by magnetic heterostructures

Nature Nanotechnology. doi:10.1038/nnano.2013.43
Authors: T. Kampfrath, M. Battiato, P. Maldonado, G. Eilers, J. Nötzold, S. Mährlein, V. Zbarsky, F. Freimuth, Y. Mokrousov, S. Blügel, M. Wolf, I. Radu, P. M. Oppeneer & M. Münzenberg
http://www.chem8.org/forum.php?mod=viewthread&tid=87025&from=portal
In spin-based electronics, information is encoded by the spin state of electron bunches1, 2, 3, 4. Processing this information requires the controlled transport of spin angular momentum through a solid5, 6, preferably at frequencies reaching the so far unexplored terahertz regime7, 8, 9. Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is used to drive spins10, 11, 12 from a ferromagnetic iron thin film into a non-magnetic cap layer that has either low (ruthenium) or high (gold) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter13 based on the inverse spin Hall effect14, 15, which converts the spin flow into a terahertz electromagnetic pulse. We find that the ruthenium cap layer yields a considerably longer spin current pulse because electrons are injected into ruthenium d states, which have a much lower mobility than gold sp states16. Thus, spin current pulses and the resulting terahertz transients can be shaped by tailoring magnetic heterostructures, which opens the door to engineering high-speed spintronic devices and, potentially, broadband terahertz emitters7, 8, 9.

Abstract-Engineering ultrafast spin currents and terahertz transients by magnetic heterostructures

http://arxiv.org/abs/1210.5372
T. Kampfrath, M. Battiato, P. Maldonado, G. Eilers, J. Nötzold, I. Radu, F. Freimuth, Y. Mokrousov, S. Blügel, M. Wolf, P. M. Oppeneer, M. Münzenberg

In spin-based electronics, information is encoded by the spin state of electron bunches. Processing this information requires the controlled transport of spin angular momentum through a solid, preferably at frequencies reaching the so far unexplored terahertz (THz) regime. Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin-current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is employed to drive spins from a ferromagnetic Fe thin film into a nonmagnetic cap layer that has either low (Ru) or high (Au) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter based on the inverse spin Hall effect that converts the spin flow into a THz electromagnetic pulse. We find that the Ru cap layer yields a considerably longer spin-current pulse because electrons are injected in Ru d states that have a much smaller mobility than Au sp states. Thus, spin current pulses and the resulting THz transients can be shaped by tailoring magnetic heterostructures, which opens the door for engineering high-speed spintronic devices as well as broadband THz emitters in particular covering the elusive range from 5 to 10THz.

Subjects:	Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Other Condensed Matter (cond-mat.other)
Cite as:	arXiv:1210.5372 [cond-mat.mes-hall]
	(or arXiv:1210.5372v1 [cond-mat.mes-hall] for this version)