Vertical Soliton-Assisted Current Switching in Extremely Thick FeGd Ferrimagnets

Current-induced spin-orbit torques (SOTs) can electrically switch magnetic films. The thickness of these films is usually limited to a few tenths of nanometers. Toward stable spintronic nanodevices, it is important to explore the upper thickness limit and to identify the associated SOT switching mechanism, if it is different from standard models. Here, we experimentally show that the SOT switching could occur in Pt(3  nm)/Fe_{0.80}Gd_{0.20}/Ta(3  nm) trilayers with a thickness of Fe_{0.80}Gd_{0.20} ferrimagnetic films up to 200 nm, all at room temperature. The contributions from the Oersted field, bulk SOTs, and thermal activation induced by Joule heating are also discussed. Through performing atomistic spin simulations, we identify the critical role of nucleation and propagation of vertical magnetic solitons along the thickness direction, which could explain such unprecedented SOT switching behaviors in extremely thick ferrimagnets. The revelation of the vertical soliton-assisted SOT switching of the extremely thick ferrimagnets can be used for miniaturizing spintronic devices.