Incoherent and coherent spin manipulation in ferromagnet - dilute magnetic semiconductor hybrids

Simon Halm 1Patric Hohage 1Frank Seifert 1Tilmar Kümmell 1Ellen Schuster 2Werner Keune 2Matthias Sperl 3Joachim Puls 4Fritz Henneberger 4Gerd Bacher 1

1. Werkstoffe der Elektrotechnik, University Duisburg-Essen, Bismarckstr. 81, Duisburg 47057, Germany
2. Angewandte Physik, University Duisburg-Essen, Lotharstr. 1-21, Duisburg 47048, Germany
3. Lehrstuhl für Magnetismus und Magnetoelektronik, University Regensburg, Universitätsstr. 31, Regensburg 93040, Germany
4. Institut für Physik, Humboldt-University Berlin, Newtonstr. 15, Berlin 12489, Germany


Hybrid systems of a semiconductor (SC) and nanostructured ferromagnets (FMs) have attracted great interest, since they allow a local control of the spin property of the SC charge carriers. Several routes are being followed to obtain a spin polarization in such hybrids, including spin injection, ferromagnetic proximity polarization or the usage of local magnetic fields. We present a scheme that employs the magnetic fringe field from nanoscale FMs with a well defined magnetization to locally manipulate the spin states in a ZnCdMnSe/ZnSe dilute magnetic semiconductor quantum well (DMS QW) both incoherently and coherently.

We demonstrate a spin analogon to the "classical" electric gate: instead of electric fields which control the local charge density, magnetic fields arising from Fe/Tb nanomagnets with remanent out-of-plane magnetization are used to locally accumulate spins of a defined orientation in a SC. In an optimized hybrid structure we obtain a spatially confined, remanent spin polarization of 12 % at 4 K. The spin polarization can be switched via magnetization of the FMs and can be observed up to a sample temperature of 80 K. Highly spatially resolved photoluminescence measurements allow a local scan of the spin polarization on a sub-micrometer scale.

By using time resolved Kerr rotation measurements, we are able to demonstrate the impact of the magnetic fringe field on the coherent magnetization dynamics in the DMS QW: Fringe fields arising from nanostructured Co FMs on top of the SC effectively modify the total magnetic field, which results in a local variation of the Mn spin precession frequency. We demonstrate that even tiny fringe fields alter the coherent spin dynamics in the SC noticeably, which implies that this technique can be used as a sensitive magnetometer for local magnetic fields.


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Presentation: Keynote lecture at E-MRS Fall Meeting 2006, Symposium E, by Gerd Bacher
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 18:29
Revised:   2009-06-07 00:44