Invalidation of the Domain Wall Depinning Model and Current‐Induced Switching Angle Shift Analysis in Pt75Ti25/Ti/Fe60Co20B20 Heterostructure

Abstract

Electrical switching of magnetization is central for spintronics but not yet well understood. Domain wall depinning has been widely believed as the mechanism of the perpendicular magnetization switching and as the principal model for quantifying the efficiency of the spin‐orbit torque in a variety of magnetic heterostructures. Here, utilizing the model devices of Pt75Ti25/Ti/Fe60Co20B20 and others with strong spin‐orbit torques and strong perpendicular magnetic anisotropy, it is reported that the switching angle shift analysis generally and considerably misestimates the spin‐orbit torque in magnetic devices. It is found that the devices exhibit strong asymmetric current switching, sharp switching by in‐plane magnetic field, considerable deviation of the coercivity from the inverse cosine scaling with the polar angle of the switching magnetic field, and rapid “ʍ”‐shaped variation of the perpendicular coercivity with the in‐plane magnetic field, which provide unambiguous evidence for a critical role of anti‐domain nucleation but against the widely believed domain wall depinning mechanism. The findings raise critical questions on any quantitative analyses based on domain wall depinning or switching angle shift.