Engineering Magnetic Domain Walls in Magnetic Nanowires

by Jansen Isabelle Heukensfeldt

Institution: Leiden University
Year: 2016
Keywords: CrO2; domain wall; ferromagnetism; nanowire; chromium dioxide; crystal growth
Posted: 02/05/2017
Record ID: 2100661
Full text PDF: http://hdl.handle.net/1887/40904


Domain wall manipulation in ferromagnets shows great promise for the development of fast and efficient computer memory devices. In particular, chromium dioxide has a half-metal characteristic that holds the potential for reducing the heat produced from reading or writing memory bits. To reliably control the motion of domain walls, CrO2 nanowires are created with geometric anisotropy that acts as a potential well to ”pin” domain walls to fixed sites. Each wire was grown using selective-area growth to avoid the creation of random pinning sites from crystal disorder. This process is sensitive to many different factors in the creation of the SiO2 mask. Different effects can interfere with each other, including the proximity effect from electron beam lithography and a sensitivity to the levels of oxygen in the doped SiO2. This thesis presents methods of correction for individual effects, as well as initial results of domain wall mechanics in CrO2 nanowires. Using MFM measurements, I show the static pinning of a domain wall at the predicted pinning location. Magnetoresistance measurements of CrO2 wires ranging from 700 nm to 900 nm wide show that, at this scale, the dominant influence on the domain wall mechanics remains the magnetocrystalline anisotropy, instead of shape anisotropy as desired. Advisors/Committee Members: Aarts, Jan (advisor).