Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 3: Spin Hall Effects

MA 3.6: Vortrag

Montag, 31. März 2014, 10:45–11:00, HSZ 403

Phase-sensitive detection of both inductive and non-inductive ac voltages in ferromagnetic resonance — •Mathias Weiler, Justin M. Shaw, Hans T. Nembach, Martin A. Schoen, Carl T. Boone, and Thomas J. Silva — Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305

Spin pumping causes significant damping in ultrathin ferromagnetic/normal metal (NM) multilayers via spin-current generation of both dc and ac character in the NM system. While the nonlinear dc component has been investigated in detail by utilization of the inverse spin Hall effect (iSHE) in NMs, much less is known about the linear ac component that is presumably much larger in the small-excitation limit. We measured generated ac voltages in a wide variety of Permalloy/NM multilayers via vector-network-analyzer ferromagnetic resonance. We employ a custom, impedance-matched, broadband microwave coupler that features a ferromagnetic thin film reference resonator to accurately compare ac voltage amplitudes and phases between varieties of multilayers. We find that inductive signals are major contributors in all investigated samples. It is only by comparison of the phase and amplitude of the recorded ac voltages between multiple samples that we can extract the non-inductive contributions due to spin-currents. Voltages due to the ac iSHE in Py(10nm)/Pt(5nm) bilayers are of the same order of magnitude as inductive signals, in agreement with recent theoretical predictions.

M.W. acknowledges financial support by the German Academic Exchange Service (DAAD).