Large damping-like torque and efficient current-induced magnetization reversal in Ti/Tb-Co/Cr structures

Seeking the magnetic heterostructures with large current-induced torque efficiency is currently one of the core hotspots in spintronics. In this work, we report the large and composition-dependent damping-like (DL) torque in the structure consisting of light metal Cr and Ti layers and a ferrimagnetic Tb-Co layer. The DL torque efficiency in the structures reaches a maximum (around -0.55) as the Tb content in the Tb-Co layer is in the range of 0.15-0.18. This composition-dependent behavior is different from that observed in the usual heavy-metal/ ferrimagnetic structures. We also demonstrated the efficient current-induced magnetization reversal in these structures with a low threshold current density down to 8 x 10(10) A/m(2). In comparison, only very low efficiency values of -0.06 and -0.086 are obtained in the Ti/Co/Cr and Ti/Tb-Co/SiN control samples, respectively, suggesting that the large DL torque in the Ti/Tb-Co/Cr structures may originate from the orbital Hall effect in the Cr metal. By fitting the Cr layer thickness dependence of the torque efficiency with a simple orbital current diffusion model, we obtained an effective orbital Hall angle of -0:57 +/- 0:02 for the Ti/Tb0.85Co0.15/Cr samples. This work demonstrated the possibility to enhance the orbital torque effect by using the magnetic layer containing the element with strong spin-orbit coupling.