Field-free spin-orbit torque switching through domain wall motion
Journal
Physical Review B
Journal Volume
100
Journal Issue
10
Pages
104441
Date Issued
2019
Author(s)
Murray, Neil
Liao, Wei-Bang
Wang, Ting-Chien
Chang, Liang-Juan
Tsai, Li-Zai
Tsai, Tsung-Yu
Lee, Shang-Fan
Pai, Chi-Feng
Abstract
Deterministic current-induced spin-orbit torque (SOT) switching of magnetization in a heavy transition metal/ferromagnetic metal/oxide magnetic heterostructure with the ferromagnetic layer being perpendicularly magnetized typically requires an externally applied in-plane field to break the switching symmetry. We show that by inserting an in-plane magnetized ferromagnetic layer CoFeB underneath the conventional W/CoFeB/MgO SOT heterostructure, deterministic SOT switching of the perpendicularly magnetized top CoFeB layer can be realized without the need of in-plane bias field. Kerr imaging study further unveils that the observed switching is mainly dominated by domain nucleation and domain wall motion, which might limit the potentiality of using this type of multilayer stack design for nanoscale SOT-MRAM application. Comparison of the experimental switching behavior with micromagnetic simulations reveals that the deterministic switching in our devices cannot be explained by the stray field contribution of the in-plane magnetized layer, and the roughness-caused Néel coupling effect might play a more important role in achieving the observed field-free deterministic switching.
Type
journal article