Gi-Hong Gim

Electric Control of Multiple Domain Walls in Pt/Co/Pt Nanotracks with Perpendicular Magnetic Anisotropy

The electric control of the motion of multiple domain walls (DWs) is demonstrated by using the Pt/Co/Pt nanotracks with perpendicular magnetic anisotropy. Because of the weak microstructural disorders with a small DW propagation field (approximately a few mT), a purely current-driven DW motion is achieved in the creep regime at current densities less than 107 A/cm2 at room temperature. It is confirmed by using a scanning magneto-optical Kerr effect microscope that several DWs are simultaneously and identically displaced by the same distance in the same direction. Utilizing such DW motion, we succeeded in realizing the writing and transferring of random bits in a device prototype of 4-bit shift registers.

Depinning Field at Notches of Ferromagnetic Nanowires With Perpendicular Magnetic Anisotropy

In this paper, we experimentally characterize the domain-wall depinning mechanism at notches of ferromagnetic nanowires with perpendicular magnetic anisotropy. A time-resolved magneto-optical Kerr effect detection reveals that the depinning time is exponentially proportional to the strength of external magnetic field. From an analysis based on Neacuteel-Brown theory, the depinning field and the activation volume are quantitatively determined for several notches with different gap distances. Interestingly, both the depinning field and the activation volume are proportional to the inverse of the gap distance. This is explained by the sizeable extrinsic effect from geometric constrictions in contrast to the intrinsic properties of the films.