Characterization of the Field-Like Term of Spin-Orbit Torque in Ta/Co/Pt by Sweeping Transverse Field

The measurement of field-like term of spin-orbit torque (SOT), which results from interface Rashba effect in heavy metal/ferromagnetic material (HM/FM), can be carried out using the harmonic measurement technique. However, most of the measurements have been carried out in ultra-thin HM/FM films with interfacial perpendicular magnetic anisotropy (PMA). In HM/FM systems with in-plane magnetic anisotropy (IMA), the interfacial anisotropy is negligible. To understand the origin of the interface Rashba effect, it is imperative to study HM/FM films with IMA. Recent studies on SOT in IMA films have reported that an in-plane transverse field sweep does not provide information of the field-like term similar to PMA systems [1]. Here, we theoretically and experimentally show that the field-like term in IMA system can be obtained by the in-plane transverse field sweep. Figure 1 shows the experimentally measured field-like term of SOT in IMA system which is obtained by the in-plane transverse field sweep. The results are consistent with the values reported in literature, where PMA is chosen.