Ferromagnetic resonance of Co thin films grown by atomic layer deposition on the Sb2Te3 topological insulator

Interfacing ferromagnetic materials with topological insulators is an intriguing strategy in order to enhance spin-to-charge conversion mechanisms, paving the way toward highly efficient spin-based electronic devices. In particular, the use of large-scale deposition techniques is demanding for a sustainable and cost-effective industrial technology transfer. In this work, we study the magnetic properties of the Co/Sb₂Te₃ heterostructure, where the ferromagnetic Co layer is deposited by atomic layer deposition on top of the Sb₂Te₃ topological insulator, which is grown by metal organic chemical vapor deposition. In particular, broadband ferromagnetic resonance is employed to characterize the Co/Sb₂Te₃ system and the reference heterostructure Co/Pt. For Co/Sb₂Te₃, we extract an effective magnetic anisotropy constant Keff=4.26∙10⁶ erg/cm³ , which is an order of magnitude higher than in Co/Pt (Keff=0.43∙10⁶ erg/cm³). The large difference in the Keff values observed in Co/Sb₂Te₃ and Co/Pt is explained in terms of the different Co crystalline structures achieved on top of Sb₂Te₃ and Pt, respectively. Interestingly, the Co/Sb₂Te₃ system displays a relatively large Gilbert damping constant (α = 0.095), which we suggest as possibly due to spin pumping from the Co layer into the Sb₂Te₃ topological insulator.