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Self-assembly of ferromagnetic micro/nano-particles with perpendicular magnetic anisotropy


Type

Thesis

Change log

Authors

Stanton, Michael Richard 

Abstract

Magnetic particles offer an interesting platform for self-assembly, as their dipolar interactions and response to magnetic fields can be used to drive and manipulate assembly. Many magnetic particles used so far in these applications are quite simple in their properties, such as iron oxide particles or magnetic colloids. To grow the potential of magnetic self-assembly, more complex particles are being developed to increase the complexity and functionality of the assemblies. In this vein, this work has created magnetic particles based on thin films of CoFeB/Pt with perpendicular magnetic anisotropy (PMA) to use for self-assembly. PMA films have been long developed for magnetic recording and computing applications, so they are well understood and optimized. Their high moment and strong anisotropy make them good candidates for a highly directional equilibrium self-assembly system. The particle construction was first optimized in films, looking at both the magnetic and structural properties needed for particles. The particles are then patterned from the film using top-down lithographic methods. Using top down methods, as opposed to the chemical synthesis methods used for most magnetic particles, is what allows the tuneable magnetic film properties to be transferred to particles. Once in liquid, the individual field response and interactions of the particles were analysed, to understand how they would best assemble. Then, the particles were assembled into 1D and 2D structures, which were then manipulated with magnetic fields to understand how these assemblies could be controlled and actuated. Assemblies of 3D structures on chip were also created and observed. These results demonstrate the fundamental assembly capabilities of the system and begin to show how it might be applied in microrobotics or micromachinery.

Description

Date

2020-10-01

Advisors

Cowburn, Russell

Keywords

magnetism, thin films, perpendicular magnetic anisotropy, self-assembly, nanotechnology

Qualification

Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Sponsorship
EPSRC (1645908)
EPSRC (1645908)
Cambridge Commonwealth, European & International Trust

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