Transmission Electron Microscopy Study of Advanced Magnetic Sensor Films

Murdoch, Susan Jane Tara (2001) Transmission Electron Microscopy Study of Advanced Magnetic Sensor Films. PhD thesis, University of Glasgow.

Abstract

This thesis begins with an overview of the phenomenon of ferromagnetism and the theory of magnetic data recording in Chapter 1. The basic concepts of ferromagnetism and antiferromagnetism are described, along with the different energy contributions which determine the properties and characteristics of ferromagnetic materials. The chapter then concludes with the introduction of the important application of spin-valves as sensor materials. Chapter 2 then goes on to introduce the instrumentation and experimental techniques adopted for the transmission electron microscopy investigations in this study. The magnetic imaging modes of Lorentz microscopy are discussed, along with the methods used to apply controllable magnetic fields in-situ within the TEM. Chapter 3 describes the fabrication of electron transparent substrates suitable for TEM investigations. It then goes on to discuss the deposition and preparation of the magnetic films of interest, including electron beam lithography patterning. In chapter 4 the physical microstructure of a selection of magnetic materials is considered. Grain size and texturing are investigated for a range of different materials of interest. Chapter 5 looks at the magnetisation reversal of single-layer NiFe films and AMR stacks. Hard and easy axis reversal behaviour of these films is investigated as a prelude to the investigation of more complex multi-layer sensor films. In chapter 6, the free- layer reversal mechanism of spin-valve material is investigated as a function of applied field orientation, and then as a function of specimen temperature. Chapter 7 investigates how the properties of a spin-valve stack vary when selected layer thicknesses are altered. This shows the importance of optimisation of a spin-valve stack, considering the properties of each layer in turn. Chapter 8 considers the reversal behaviour of micron-sized patterned elements of spin-valve material. Elements of different shapes, aspect ratios and orientation relative to the biasing direction are considered. Finally chapter 9 discusses the conclusions which can be drawn from this work, and finishes by considering some possible further work which would extend the investigations carried out here.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: John Chapman
• Keywords: Electromagnetics, Condensed matter physics
• Date of Award: 2001
• Depositing User: Enlighten Team
• Unique ID: glathesis:2001-76097
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 16:39
• Last Modified: 19 Nov 2019 16:39
• URI: https://theses.gla.ac.uk/id/eprint/76097