metres and below, more than five hundred times smaller than
the width of a human hair -- the geometric shape of the object
becomes more important; the smaller the object, the more strongly the
shape anisotropy affects the hysteresis loop.
This thesis reports on investigations of these magnetic nanostructures.
Chapter 2 briefly summarises the origins of magnetism, the applications of micromagnetism in modern digital data storage -- specifically hard disk media and magnetoresistive random access memory -- and some of the theories behind micromagnetics pertaining to our simulation work. Additionally, this chapter covers the methods we use in more detail with respect to geometry and computation, and also touches on post-simulation visualisation.
Chapter 3 investigates the properties of basic primitives. We study numerically the magnetisation reversal of a flat cylinder and a sphere, and provide studies of size dependence for these geometries.
Chapter 4 discusses the magnetic reversal behaviour of conical particles, and presents a magnetisation remanence phase diagram as a function of diameter and height.
Chapter 5 considers the simulation of ``nanodots''. These tiny part-spherical geometries can be formed through a chemical self-assembly double template method, and numerical studies assist with the interpretation of experimental data.
In Chapter 6, we study the magnetic behaviour of close-packed spherical holes, or antispheres, produced through a self-assembly template method.
Finally in Chapter 7 we summarise our findings and provide an outlook for future research.