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Current Current-induced Spinwave Dynamics : An Optical Approach

Jean-Yves Chauleau, Universität Regensburg


Action of spin-polarized electric currents on magnetic textures is now well established both from experimental and theoretical viewpoints [1]. These effects are known as spin-transfer torques (STT). In the case of continuous magnetic distributions, current-induced domain wall (DW) dynamics is a recurrent system of investigation. However, DWs are fairly complicated magnetic structures whose dynamics is consequence of a subtle combination of damping, spin-drift velocity and non-adiabatic parameter. An alternative to domain walls dynamics has been reported by Vlaminck and Bailleul. The current-induced shift of spinwave resonances (spinwave Doppler shift) has been experimentally evidenced using an inductive approach [2].

In this study, we demonstrate the ability of time-resolved scanning Kerr microscopy (TRMOKE) to investigate the spin-transfer torque effects on propagating spinwaves in Permalloy stripes. This approach allows not only the measurement of the full wave’s spectrum but also a direct imaging of the different modes present in the stripe. Wavevector, damping length and group velocity and their current-induced changes are directly measured experimentally in the same magnetic structure leading to a fully self-consistent determination of the three parameters which govern current-induced magnetization dynamics.

 

References :

[1] D. C. Ralph and M.D. Stiles, J. Magn. Magn. Mat., 3212508 (2009)

[2] V. Vlaminck and M. Bailleul, Science, 322410 (2008)