Institut des
NanoSciences de Paris

Soutenance de thèse de Piotr Kuszewski - Vendredi 9 novembre 2018 à 14h

Piotr Kuszewski, doctorant dans l’équipe Photons - Magnons et Technologies Quantiques (PMTeQ) soutient sa thèse le vendredi 9 novembre 2018 à 14h.

INSP - Sorbonne Université - 4 place Jussieu - 75005 Paris - Barre 12-22 - Rez-de-Chaussée - Salle 08

« Optical detection of magneto-acoustic dynamics »

In the developing field of spin wave-based information technology, this work investigates the possibility to use surface acoustic waves (SAW) to excite spin-waves in ferromagnetic thin layers relying on the magnetoelastic coupling. This would provide a non-inductive, efficient, and remote addressing of spin waves. In this thesis the surface acoustic waves are excited electrically and optically. In both cases, the magneto-acoustic signal is detected optically.

With the electrically excited SAWs, we investigate the resonant magneto-elastic coupling in a thin film of the ferromagnetic semiconductor (Ga,Mn)As. We disentangle the photoelastic contribution from the magneto-optical one, from which we obtain the amplitude of magnetization precession. Its field dependence is shown to agree well with theoretical calculations. Its amplitude resonates at the same field as the resonant attenuation of the acoustic wave, clearly evidencing the magneto-acoustic resonance with high sensitivity. The influence of temperature, SAW frequency and power on the coupling efficiency are studied.

In the second project we use SAWs thermoelastically excited by a tightly focused laser beam on ferromagnetic metals (Ni, FeGa, Co) on a transparent substrate (glass, sapphire). Spatio-temporal maps of the surface displacement and magneto-optical signal are obtained. The dispersion relation is used to disentangle the magnetic contribution in the signal.


Olivier Klein, CEA
Thomas Pezeril, Université du Maine
Sarah Benchabane Gaiffe, FEMTO-ST
Karine Dumesnil, Institut Jean Lamour
Massimiliano Marangolo, INSP
Co-directrices de thèse : Catherine Gourdon et Laura Thevenard, INSP