Effect of Ru Underlayer on High In-plane Anisotropy Field of FeCoB Layer

Abstract

We investigated how a Ru underlayer contributed to the in-plane magnetic anisotropy of an FeCoB upper layer. The Ru underlayer with a higher degree of Ru (001) orientation induced higher in-plane magnetic anisotropy in the FeCoB upper layer. A Si/NiFe seed layer, which was located beneath the Ru underlayer, changed the Ru crystalline orientation from random to (001) preferential orientation and induced a remarkably high in-plane anisotropy field of 540 Oe. The in-plane anisotropy of Ru crystallites in the Ru underlayer is discussed in the paper. The Ru (002) pole_figure indicated isotropic in-plane alignment of Ru crystallites. Si/NiFe/Ru/FeCoB film was prepared using two methods, i.e., with unturned and turned underlayer deposition. The direction of anisotropic alignment of FeCo crystallites and in-plane magnetic anisotropy of the FeCoB layer was not influenced by the direction of the Ru underlayer; therefore, the Ru underlayer was not a dominant factor, and the oblique incidence effect caused by the configuration of Facing Targets Sputtering system (FTS) was a dominant factor that induced in-plane magnetic anisotropy in the FeCoB layer. The Ru underlayer may have contributed to an increment of the oblique incidence effect.