Hf Thickness Dependence of Interlayer Exchange Coupling and High-Frequency Performances in Magnetic Anisotropic Fecob/Hf/Fecob Trilayers

It was reported that the dynamic interlayer exchange coupling (IEC) can effectively enhance the ferromagnetic resonance (FMR) frequency in the ferromagnet/nonmagnet/ferromagnet trilayers. In this study, the nonmagnetic Hf was chosen as a spacer to explore its effects on the IEC and FMR frequency. The FeCoB(25nm)/Hf( [[EQUATION]] )/FeCoB(25nm) trilayers with various Hf thickness were prepared by a compositional gradient sputtering method for obtaining self-biased high-frequency characteristics. It is revealed that the resonance frequency is increased by the IEC. A ferromagnetic (FM) coupling appears at [[EQUATION]] 3.68 nm, while an antiferromagnetic (AFM) coupling dominates at [[EQUATION]] 3.68 nm. The strongest FM coupling occurs at [[EQUATION]] 3.68 nm with a coupling coefficient J 1 of +0.3 erg/cm 2 . In contrast, a strong AFM coupling appear around [[EQUATION]] 4.41 nm with a coupling coefficient J 1 of -0.52 erg/cm 2 . The coupling mechanism is simulated with Layadi’s rigid model and the simulation is consistent with the experimental results well