Room temperature spin-orbit torque switching induced by a topological insulator
2018
Recent studies on the topological insulators have
attracted great attention due to the rich spin-orbit physics and
promising applications in spintronic devices. The strongly
spin-moment coupled electronic states have been extensively pursued
to realize efficient spin-orbit torque switching. However, so far
current-induced magnetic switching with topological insulators has
been observed only at cryogenic temperatures. Whether the
topologically protected electronic states in topological insulators
can benefit to spintronic applications at room temperature remains
a controversial issue. In this thesis, spin-orbit-torque-induced
magnetic switching is realized in topological insulator/ferrimagnet
heterostructure at room temperature. Ferrimagnetic CoTb alloy with
robust bulk perpendicular magnetic anisotropy is directly grown on
a classical topological insulator Bi2 Se3. The low switching
current density provides definitive proof of the high spin-orbit
torque efficiency from topological insulators. The comparison
between Bi2Se3 and (Bi,Sb)2Te3 with less bulk conductivity suggests
the surface states plays a significant role in generated the
efficient spin-orbit torques. Furthermore, the effective spin Hall
angle of topological insulators is determined to be several times
larger than commonly used heavy metals. These results demonstrate
the robustness of topological insulators as a spin-orbit torque
switching material and provide an avenue towards applicable
topological insulator-based spintronic devices.
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