Yicheng Guan obtains summa cum laude for his PhD

Congratulations to Yicheng Guan!

Title: "Increased efficiency of current-induced chiral domain wall motion by interface engineering"

Abstract

Racetrack devices based on chiral domain wall magnetic bits in perpendicularly magnetized ferromagnet/heavy metal thin film systems are promising candidates for next-generation spintronic memories. Néel type domain walls are stabilized in such devices by an interfacial Dzyaloshinskii-Moriya interaction. These Néel type domain walls can be readily manipulated by the injection of spin currents generated from electrical currents in the heavy metal layers. More efficient current-induced domain wall motion is needed for commercially viable, fast, and low power racetrack memory devices. In this thesis we demonstrate significantly increased efficiency of domain wall motion with substantially lowered threshold current densities and enhanced domain wall velocities by the introduction of atomically thin 4d and 5d metal “dusting” layers at the ferromagnetic/heavy metal interfaces. The greatest efficiency is found for dusting layers of Pd and Rh, just one monolayer thick at Pt/Co interfaces, for which the domain wall’s velocity is increased by up to a factor of 3.5. This is due to a subtle interplay of several spinorbitronic parameters. This thesis demonstrates a path to increased efficiency of chiral domain wall motion by tailored interfaces in racetrack devices.