Date of Award

2012

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Engineering

Faculty

Computing, Health and Science

First Advisor

Professor Kamal Alameh

Second Advisor

Dr Mikhail Vasiliev

Abstract

This work explores the preparation, characteristics and properties of highly bismuth (Bi) substituted, metal doped, iron garnet compounds and investigates their potential for various emerging applications in the visible and near infrared spectral regions.

Bi-substituted iron garnet and garnet-oxide nanocomposite films of generic composition type (Bi, Dy/Lu)3(Fe, Ga/Al)5O12 are prepared by using a radio frequency (RF) magnetron sputtering technique. The physical properties (crystallinity, film morphology, optical absorption spectra across the visible spectral range and the elemental composition of layers), and magneto-optic behaviour (Faraday rotation, hysteresis loops of Faraday rotation, and magnetic switching behaviour) of these sputtered garnet films are investigated in this work. These garnet materials possess high quality nanocrystalline thin-film microstructures and demonstrate excellent combination of optical and magneto-optical (MO) properties which makes them very attractive for use in magneto-optical applications. Record-high MO performance, in terms of the material’s MO figures of merit achieved (which exceeded most or all of the values reported previously for any semi-transparent MO materials across most of the visible spectrum), is achieved simultaneously with high Faraday rotation, making them suitable for a wide range of applications in integrated optics and photonics. The effects of annealing on the garnets of type (Bi,Dy)3(Fe,Ga)5O12, when performed in air atmosphere, are investigated and a systematic study is conducted to figure out the annealing behaviour and the crystallization kinetics of garnet formation within the garnet-bismuth oxide nanocomposites. Also, several nano-engineered magnetooptically active heterostructures (all-garnet multilayer-type thin film structures) based on magnetic layers with dissimilar uniaxial (Ku > 0) and in-plane (Ku < 0) magnetic anisotropies are prepared with the purpose of achieving the customised magnetic behaviour and properties (not attainable in single garnet layers) which are very attractive for the development of MO sensing devices and ultra-fast switches.

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