Domain wall dynamics in engineered multilayer magnetic nanostructures

• Main Author: Lin, Eddy Junxiang
• Other Authors: Lew Wen Siang
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2014
• Subjects: DRNTU::Science::Physics::Electricity and magnetism
• Online Access: http://hdl.handle.net/10356/60000
• Institution: Nanyang Technological University

Magnetic domain walls is the cornerstone for novel non-volatile storage and logic devices. These devices offer innumerable advantages such as low power consumption and high integration densities. The realisation of domain wall based devices requires better understanding of the domain wall structure and dynamics. The ability to manipulate and control high speed domain wall in nanowire networks is crucial. In this work, the domain wall dynamics in modulated nanowires with perpendicular magnetic anisotropy is investigated. The interaction of perpendicular and in-plane anisotropy on the domain wall is also studied. It is shown that the interaction of perpendicular and in-plane anisotropy in nanowires may result in faster domain wall propagation in the perpendicular magnetic anisotropy material. The structure comprises of a perpendicular magnetic anisotropy nanowire with Co60Fe20B20, a nonmagnetic spacer layer, and a permalloy strip. For spacer layer thickness less than 4nm, the domain wall was observed to have a much higher speed as compared to that in a single Co60Fe20B20 nanowire. This is attributed to the spins of the domain wall in Co60Fe20B20 aligning along the magnetic moment of the permalloy strip above it. This preferred alignment of the domain wall configuration is favoured as it decreases the exchange energy of the whole stack. For spacer layer thickness more than 9 nm, the spins within the permalloy and the domain wall in the Co60Fe20B20 favours a flux closure configuration, leading to lower domain wall speed. The nanowire structure was fabricated and the injection of domain walls was carried out experimentally together with the measurement of the domain wall magnetoresistance.