In recent years, there has been an explosion in the realisation of incorporating magnetic devices into micro-electro-mechanical-systems, where both the magnetic sensor and its associated electronic operating circuitry are fabricated on a single substrate. This not only allows the miniaturisation of the sensor elements, as dictated by technological demands for smaller and smaller electrical components, but also enables the same micro-fabrication technologies to be used in both the production of the electronic and the magnetic devices. This makes it commercially more attractive due to the reduced costs and the applicability to a wider range of systems.

Magnetic sensors have been utilised for many years now. The advent of the technologies of micro-fabrication and thin film deposition, has allowed the production of more sophisticated magnetic field and stress sensors; these include exotic, three dimensional magnetic sensors; such as, cantilevers, bridges and membrane devices, which have been coated with magnetostrictive films, thus allowing the detection of stress.

There has been extensive research into amorphous materials in melt-spun ribbon form, which exhibit excellent magnetic properties: large saturation magnetostriction, high saturation magnetisation, low anisotropy energies and low coercivity. These factors have made amorphous ribbon materials excellent candidates for sensors and actuator devices. Commercial organisations such as Allied-Signal and Vacuumschmelze now produce a wide selection of melt-spun alloys which are used in a range of applications. Despite their excellent magnetic properties generally, the as-cast melt-spun ribbons suffer from high randomly orientated stresses, which give rise to a complicated domain structure. However, it is well established, that in the stress relieved or magnetically annealed state, they exhibit excellent soft magnetic properties. The disadvantages of these ribbon materials are, that they need to be annealed in an oxygen-free environment to prevent oxidation, some ribbon materials become brittle on annealing, they are difficult to incorporate into sub-millimetre dimensional devices and, most importantly of all, there is no suitable means of bonding such materials onto micro-fabricated structures; the ribbon materials are currently bonded to larger devices using epoxy resin. However, it is found that the optimised domain structure obtained by magnetic annealing is disturbed by the curing epoxy resin, which induces stress into the ribbon.

This thesis is concerned with producing FeSiBC films of similar composition to that of the amorphous METGLAS^® 2605SC target material (Fe₈₁Si_3.5B_13.5C₂) which exhibits excellent soft magnetic properties and are ideal for device applications. The films were deposited by RF magnetron sputtering onto commercially important substrates which will, therefore, allow the present/future design of sophisticated devices, and eliminate the problem of bonding the magnetostrictive material to the device.

The chapters within the thesis are generally self-contained, where the literature review, results, discussions and conclusions are presented within the one chapter.

The following chapter (2) is concerned with the construction of a magnetometer and imaging system based on the Magneto Optical Kerr Effect; this was found to be essential for the study and characterisation of the amorphous FeSiBC films. The general principles of the Kerr effect have been discussed, providing the reader with a sufficient insight into the implementation of the Kerr effect, and therefore allowing one to interpret the data from the two techniques presented in this thesis.

Chapter 3 provides a general description of the experimental techniques which have been employed to prepare, analyse and characterise the magnetic films.

Chapter 4 deals with the process of sputter deposition. The deposition technique is discussed and it is shown that the deposition of films by sputtering is a complex process which is strongly dependent on many parameters. Films have been deposited onto commercially important substrates such as GaAs, Si and Si₃N₄, which are compatible with the microelectronic fabrication technologies. This may allow the fabrication of both the magnetic sensor and the electronic detection system on the one substrate, making it commercially more attractive. The general magnetic properties of amorphous films deposited by sputtering are also presented.

Chapter 5 is concerned with the magnetic anisotropy of amorphous FeSiBC films which have been deposited by RF magnetron sputtering, mainly at the optimised sputtering parameters. The magnetic properties were investigated principally using the magneto-optical Kerr effect, with both point hysteresis measurements and domain imaging. A significant in-plane anisotropy was observed in the as-deposited films; this has been attributed to the residual field from the magnetron sputtering source. The effects of various treatments on the films are investigated, including the use of forming fields, stress and thermal processing. The treatments are evaluated for their potential to control the anisotropy in magnetostrictive device applications.
A simple new technique is also described for the measurement of the saturation magnetostriction in amorphous thin films deposited onto rigid substrates.
A high degree of control is also demonstrated in tailoring the anisotropy field, using the technique of substrate straining.

Chapter 6 is an investigation into the Magneto Impedance effect in FeSiBC films grown in this study. The objective was to ascertain the potential use of FeSiBC films for Magneto Impedance sensors and to correlate the magnetic properties with that of the impedance responses.

A summary of the conclusions and further work is presented in Chapter 7.