Various magnetic behaviors at the interface between heavy metals and ferromagnets

Abstract

At the interfaces between heavy metals such as Pt, Ir and ferromagnets, a strong spin-orbit coupling (SOC) plays an important role in various magnetic phenomena such as perpendicular magnetic anisotropy (PMA), magnetostriction effects, anomalous Hall effects, anisotropic magnetoresistances (AMR), and magnetic damping processes. [1,2] Recently, the interfacial Dzyaloshinskii-Moriya interaction (DMI), a new interface effect originated by a strong SOC, has been of great interest because of its interesting physical roles in the chiral spin configuration in PMA system such as Neel-type domain wall and a nanomagnetic skyrmion. Both spin structures are very promising candidates for future information-processing devices with high efficiency and ultrahigh density data storage abilities. In this study, various magnetic properties are systematically investigated by performing Brillouin inelastic light scattering (BLS) spectroscopy. First of all, we demonstrate that the strength of the interfacial DMI is strongly depend on the quality of interface and a buffer layer can enhance not only the interfacial DM energy density over 58%, but also the PMA energy density over 103% (See Fig. 1(a)). [3] As another interface effect, the effective spin pumping at spin-orbit coupled Ir/Co interface is also investigated. Although, the measured interfacial DM energy density is relatively smaller than the case of the Pt/Co system, but the saturation magnetization (Ms) and the surface magnetic anisotropy (Ks) are significantly enhanced due to a higher proximity-induced magnetization effect (See Fig. 1(b)). From the systematic BLS measurements, the magnetic damping constants (α) can be clearly deduced and the key finding is that the interfacial DM contribution in the enhancement of the damping constant can be ruled out. [4]