Dilute magnetic semiconductors (DMSs) are ideal candidates for spintronic devices as they exhibit both semiconducting and magnetic properties. The defining feature of a DMS material is the exchange interactions between the magnetic ions and the band electrons and holes, which leads to many of the spin behaviours observed. A fundamental property of DMSs is that a relatively small external magnetic field can cause enormous Zeeman splittings of the electronic energy levels, which allows separating of states with differentspins. The giant Zeeman effect present in the DMS systems also leads to the possibility of trapping quasiparticles in an inhomogeneous magnetic field.In this thesis the effect of inhomogeneous magnetic fields on excitons in a DMS quantum well is investigated. We look at the possibility of trapping excitons in hybrid structures composed of a DMS quantum well placed a few nanometres below a nanoscale and microscale ferromagnetic disk and a ferromagnetic strip. Quasiparticles in a DMS quantum well are shown to undergo a splitting between band states for different spin components due to the giant Zeeman interaction. Due to the inhomogeneous magnetic field created by a nanoscale ferromagnetic disk in the vortex state the quasiparticles are found to be confined in a small region on the quantum well. The behaviours of excitons in the presenceof both a homogeneous and inhomogeneous magnetic field is then discussed. The binding energy of a heavy hole exciton in a finite DMS quantum well in the presence of a homogeneous is calculated. The study is extended to look at excitons in the presence of an inhomogeneous magnetic field. The behaviour of excitons in the presence of a inhomogeneous magnetic field, is found to depend on the type of magnetic field, and is shown to be different for a magnetic field created by a microscale and nanoscale ferromagnetic diskand a ferromagnetic strip.
|Date of Award||15 Jan 2014|
|Sponsors||The Leverhulme Trust|
|Supervisor||Simon Crampin (Supervisor)|