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DS: Fachverband Dünne Schichten

DS 12: Postersession DS

DS 12.25: Poster

Montag, 7. März 2016, 17:00–19:00, Poster A

Elastic dynamics in CoFeB/MgO multilayers: Excitation and suppression of THz phonons — •Dennis Meyer¹, Markus Müller¹, Henning Ulrichs¹, Maria Mansurova^1,2, Jakob Walowski², and Markus Münzenberg² — ¹I. Physikalisches Institut, Georg-August Universität Göttingen — ²Institut für Physik, Ernst Moritz Arndt Universität Greifswald

When thin films are impinged by a laser pulse, the thermal stress induced at the surface triggers coherent elastic waves which subsequently propagate through the sample. We present a combined experimental and numerical investigation of such dynamics in a CoFeB/MgO multilayer. Experiments were carried out by time-resolved pump-probe spectroscopy. The main finding is the appearance of a 0.5 THz phonon mode, which is a Bloch-like eigenmode of the system. By breaking the translational symmetry of the superlattice, this mode can be effectively suppressed. These findings are supported by numerical simulations, which in addition provide spatial information inaccessible by experiment. Besides being a building block for photo-induced THz phononics, we will discuss in how far such phonon blocking structures can be utilized for controlling heat flow in thin films.