Theoretical studies of stray field images of magnetic systems

Abstract

Research in magnetic recording is currently at a stage where an understanding of the magnetic microstructure of recording media is vitai for the continual improvement in recording performance and the achievement of higher recording densities.
Experimental techniques such as Lorentz Imaging and Magnetic Force Microscopy provide powerful tools to achieve help these objectives.
This thesis provides a theoretical study of the relationship between magnetic systems and their microstructures by developing models to simulate the imaging of such systems. An important aspect of the recording process is the design and
manufacture of head systems to improve the read/write process. Lorentz Imaging of recording heads is used to characterise the stray field profile of such components; we have developed a theoretical model which predicts the major characteristics of
the stray field profile of a thin film recording head.
A major part of the thesis is devoted to the simulation of magnetic reversal and imaging of longitudinal thin films. This has been carried out by considering a system of interacting grains positioned on an irregular physical structure; previously,
micromagnetic models have been based on Hexagonal Close Packing structures. This enables the investigation into the effect of physical structure on the macromagnetic properties of such systems.
We have developed theoretical models to simulate the imaging of longitudinal thin film. Both the simulated Lorentz and Magnetic Force Microscopy images highlight features caused by the underlying physical structure. This analysis contributes
to an explanation of the relationship between magnetic inicrostructure, physical structure and images of magnetic systems; it provides a wider context for the discussion of experimental data.