Magneto-Optic and Ellipsometric study of nanostructured media

The proposed research is concerned with the fabrication of structured arrays of nanoscale tubes and rods composed of ferromagnetic materials. These will be prepared by recently developed techniques using the in-filling of cylindrical pores created by the anodisation of thin, sputter-deposited aluminium films. The manufacturing technique has been developed considerably in Belfast and given rise to media with exciting new optical properties. The anisotropic optical properties of the arrays will be investigated using variable angle, spectroscopic ellipsometry and reflectance and transmittance photometry. The objective will be to attempt to characterise the optical properties in terms of their fundamental complex permittivity tensor. The magnetic properties will be examined in terms of their hysteresis behaviour and this will be followed by a comprehensive examination of their magneto-optical effects. In particular we will refurbish an existing Kerr polarimeter to enable fully automatic collection of both complex Kerr (reflection) and Faraday (transmission) effects. This will enable us to assess the potential of the media for suitable applications and provide basic data on the magneto-optic parameters. An attempt will be made to characterise the materials in terms of the complex Voigt parameter and its variation with wavelength over a wide spectral range. It is hoped that the array design parameters will give control over their optical properties in a way that may make them suitable for magneto-optic enhancement to generate extra-large Kerr effects that may lead to improved devices for optical isolators and for the production of arrays of ultra-fast magneto-optic switches for future 3D/HD displays of the type used in cinemas and other public displays.Fundamental to the success of this project will be the accompanying theoretical modelling of the optical and magneto-optical properties of the nanostructures and their assembly in planar arrays. Significant progress has been made in this regard using modified effective medium theories specifically adapted to take into consideration the anisotropic nature of the medium. These effective medium theories will be extended to take into account the magneto-optical activity of the magnetic component/s of the structures and it is hoped that we will have similar success in explaining the observable linear, first-order, magneto-optical effects. In addition, we will also make use of a commercial (Comsol) Multiphysics Modelling and simulation package for modelling optical properties that is based upon finite element analysis and which has already proved very useful. It remains to be seen if this can be extended to deal with magneto-optical properties.

The research being proposed is of both fundamental and practical importance and linked in with the current developments of material science on the nanoscale. To exploit any novel optical or magneto-optical properties of the nanoscale structures, basic predictive theory and physical understanding are essential. Likewise the technological skills in self-assembly and size effects are majors areas of interest to industry. At this early stage it is the academic research community that will have greatest interest in the output from this work. Nevertheless, its practical significance will not go unnoticed by those industries who are already seeking to take advantage of the novel optical and photonic properties that such structures exhibit. It seems likely that similar interest will be shown in any unique magneto-optical properties that are expected to be revealed and any developments in the self-assembly processes themselves. This is particularly the case where such processes are compatible with thin film technologies that can be incorporated into existing silicon-based technologies. The Belfast team is well placed to play a significant role in driving such work along and already holds and operates IPR sensitive activities as part of its overall programme. The university has a well established IPR protection programme and we are therefore confident existing and future advances are available for exploitation by the UK. Of particular potential is the development of new MO media that may have controllable magnetic, optical and magneto-optical properties that may well make them suitable for ultra-fast, dynamic, light engines and switching applications where giant MO effects are desirable. These may be obtained when low absorption MO media are placed into carefully designed optical multilayer structures. In this respect we have already been carrying out preliminary work with an Australian/European based company Panorama Synergy Ltd. Designs based on near transparent materials have shown great potential in this regard and a small Technology Strategy Board grant was recently obtained to pursue the work. It is clear however, that there is a real need for novel magnetic materials to facilitate the fabrication of such devices. As the proposed research progresses we will liaise with the company where and when appropriate in order to exploit any opportunities that may arise as the work progresses. In that case QUB will seek additional funding internally from the Investors of the Company and externally from research granting bodies. In addition, the work will largely be carried out in the new Seagate Research Centre within the IRCEP building (to be officially launched in June 2010) and, as such, the emerging results will have immediate exposure to industrialists of a very high calibre.