In order to understand the effect of spin-transfer-torque (STT) on artificial magnetic structures, STT-induced and magnetic field-induced ferromagnetic resonances (FMRs) were investigated for Fe/Cr/Fe layers with an antiferromagnetic coupling field. The magnetic field-induced FMR showed high resonant frequency at zero magnetic field owing to the antiferromagnetic coupling field. FMR modes characteristic of antiferromagnetic coupling were induced by STT. From the STT-FMR spectra, the critical current density for magnetization instability was estimated to be ∼7× 107 A/ cm2, suggesting the possibility that STT gives rise to the dynamic phase of magnetization in such artificial magnetic structures.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)