Spin relaxation in multilayers with synthetic ferrimagnets

Dmytro M. Polishchuk, Taras I. Polek, Akashdeep Kamra, Anatolii F. Kravets, Alexandr I. Tovstolytkin, Arne Brataas, Vladislav Korenivski

Published 2018-06-28Version 1

We demonstrate a strong tunability of the spin-pumping contribution to magnetic damping in a thin-film ferromagnetic free layer interfaced with a synthetic ferrimagnet (SFM), acting as a spin-sink, via a thin Cu-spacer. The effect strongly depends on the magnetic state of the SFM, a trilayer structure composed of two Fe layers coupled via indirect exchange mediated by a Cr spacer. With increasing Cr thickness, the SFM state undergoes a transition from antiparallel via non-collinear to parallel configuration. The corresponding non-monotonous dependence of spin relaxation in the free layer is understood in terms of a modulation of the longitudinal spin transport as well as relaxation of the transverse angular momentum in the SFM. The obtained results should be useful for designing high-speed spintronic devices where tunability of spin relaxation is advantageous.