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 Co/Pt heterostructure. For Co/Sb2Te3, we extract an effective magnetic anisotropy constant K = 4.26*10^6 erg / cm^3, which is an order of magnitude higher than in Co/Pt (Keff = 0.43*10^6 erg / cm^3). 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 (? = 0.095), which we suggest as possibly due to spin pumping from the Co layer into the Sb2Te3 topological insulator.