Graham Smith

Characterising charge carriers and traps in organic semiconductors using ESR. (Electron Spin Resonance)

High Magnetic Field Electron Spin Resonance.
This is an enabling technique in the study of paramagnetic systems (transition metal ions, free radicals, defects) in materials science and structural biology offering higher resolution, higher sensitivity and higher energy quanta. At St.Andrews we have used the expertise within the millimetre wave and magnetic resonance groups to construct a highly sensitive quasi-optical spectrometer that works from 80 to 300GHz in magnetic fields up to 12T at cryogenic temperatures. This spectrometer has state of the art sensitivity and is now a UK EPSRC facility and part of a European network on High Field ESR Instrumentation and research. The spectrometer has also been commercialised and several versions are now being used at leading laboratories around the world

High Field Ferromagnetic Resonance.
This is the study of ferromagnetic resonance in very high magnetic fields and uses the same type of spectrometer as for high field ESR measurements. Multi-frequency measurements in high fields allow anisotropy fields and damping terms to be calculated which are important parameters in the characterisation of magnetic storage media. The extra sensitivity available with the high field spectrometer has allowed very thin films to be characterised under conditions of full saturation and is very much an enabling technique

Magnetic Resonance Force Microscopy (MRFM).
This is a new technique that combines the spatial resolution of scanning probe microscopy with the chemical specifity associated with electron spin resonance. The magnetic resonance group is currently constructing a probe that works in high magnetic fields, low temperatures and in vacuum and should have a spatial resolution of around 10nm. Initial experiments have been very promising and point to the to the possibility of single spin sensitivity. If this can be achieved there are major applications in surface chemistry, ferromagnetic systems, semiconductor characterisation and structural biology.

For further information, see the High Field ESR web-site.