Ru thickness-dependent interlayer coupling and ultrahigh FMR frequency in FeCoB/Ru/FeCoB sandwich trilayers

Abstract

The antiferromagnetic (AFM) interlayer coupling effective field in the ferromagnetic/non-magnetic/ferromagnetic (FM/NM/FM) sandwich structures, as a driving force, can dramatically enhance the ferromagnetic resonance (FMR) frequency. Changing the non-magnetic spacer thickness is an effective way to control the interlayer coupling type and intensity, as well as the FMR frequency. In the study, FeCoB/Ru/FeCoB sandwich trilayers with Ru thickness (t Ru ) from 1 to 16 Å were prepared by a compositional gradient sputtering (CGS) method. It was revealed that a stress induced anisotropy is present in FeCoB films due to the B composition gradient in the samples. A t Ru dependent oscillation of interlayer coupling from FM to AFM with two periods was observed. An AFM coupling occurs in the range of 2 Å ≤ t Ru ≤ 8 Å and over 16 Å, while a FM coupling is present in the range of t Ru < 2 Å and 9 Å ≤ t Ru ≤ 14.5 Å. It is interesting that an ultrahigh optical mode (OM) FMR frequency in excess of 20 GHz was obtained in the sample with t Ru = 2.5 Å under an AFM coupling. The dynamic coupling mechanism in trilayers was simulated, and the corresponding coupling type at different t Ru was verified by Layadi's rigid model. This study provides a controllable way to prepare and investigate the ultrahigh FMR films.

Spin transport characteristics modulated by the GeBi interlayer in Y3Fe5O12/GeBi/Pt heterostructures

“…We measured the FMR linewidth (∆H) as a function of the microwave frequency ( f ) of bare YIG, YIG/Pt and YIG/Ge 1−x Bi x /Pt samples, as shown in Fig. 2(a) and fitted according to [25][26][27][28]…”