HTSC

Research

Our current areas of research interest include:

• Superconducting metamaterials for near field microscopy applications
• Thin film processing and phase stability in Fe(Se,Te) superconductors
• Fabrication and microstructural characterisation of Tl-2212 thin films for device applications
• Isolation of naturally occurring grain boundaries in high temperature superconducting tapes
• Magnesium diboride superconductor

Superconducting metamaterials for near field microscopy applications

Dr. Susie Speller, Mr. Faraz Sayed, Dr. Chris Stevens*, Prof. David Edwards*, Prof. Chris Grovenor

Novel Magnetic Resonance Microscopes have been designed to offer dramatic improvements in 3D imaging for medical and biological applications. A sub-wavelength tapered waveguide structure enables the sensing of local magnetic fields. This "metaprobe" is ideally fabricated from superconducting materials to maximise the sensitivity of the instrument. This research project is concerned with the demonstration of practical methods to fabricate complex 3D arrays of superconducting resonator devices by growing and patterning thin films of Tl-2212 superconductor on curved substrates.

We have demonstrated the fabrication of  Tl-2212 films on the curved surface of cylindrical MgO substrates with c-axis aligned radially everywhere, as desired for this type of application.  Current work focuses on improving the microstructure of these curved films by controlling the processing parameters and designing a lithography system for patterning 3D device structures such as spirals.

(*Engineering Dept., Univ. of Oxford).(Funded by Royal Academy of Engineering / EPSRC)

Thin film processing and phase stability in Fe(Se,Te) superconductors

Dr. Susie Speller, Miss Canan Aksoy, Miss Meltem Saydam, Prof. Chris Grovenor

In 2008 an entirely new class of high temperature superconducting compounds containing iron was discovered.  In the subsequent few months a great number of different iron-based superconducting phases were synthesised.  This project involves the fabrication and microstructural characterisation of the simplest of these compounds based on FeSe in bulk and/or thin film form.  Up to 50% doping of the Se site with Te is known to increase the critical temperature of these compounds, but the there is considerable variation in the properties of samples made by different groups.  Our aim is to use sophisticated microanalysis techniques to determine the local phase chemistry in bulk and thin film Fe(Se,Te) samples fabricated in-house and single crystals made elsewhere, to aid the understanding of the unusual magnetic and superconducting phenomena observed in these materials, enabling the fabrication of higher quality samples by optimising the processing strategies and chemical doping.

(In collaboration with Prof. Andrew Boothroyd and Dr. Amalia Coldea from the Department of Physics, University of Oxford and Dr. Gavin Burnell, University of Leeds.)

Growth and microstructural characterisation of Tl-2212 thin films for device applications

Mr. Michael Korsah, Dr. Sajid Saleem*, Dr. Paul Warburton*, Prof. David Edwards**, Dr. Chris Dark, Dr. Susie Speller, Prof. Chris Grovenor

For many years the HTS group has specialised in the processing of Tl-based superconducting thin films, studying how processing parameters influence the microstructure of the film and hence its electromagnetic properties.  This understanding of processing/property relationships allows film properties to be tailored for a range of device applications from large area microwave filters (in collaboration with Prof. David Edwards in the Engineering Science Department**) to Intrinsic Josephson Junction devices (in collaboration with Dr. Paul Warburton's group at UCL*).

Isolation of naturally occurring grain boundaries in high temperature superconducting tapes

Dr. Susie Speller, Dr. Marcus Weigand*, Prof. Chris Grovenor, Dr. John Durrell*

The current carrying performance of high temperature superconducting tapes is known to be strongly influenced by grain boundaries.  This project takes a new approach to studying the properties of real grain boundaries in HTS tapes and involves the use of EBSD analysis and FIB machining to isolate naturally occurring grain boundaries in superconducting tapes.  The superconducting properties of the isolated grain boundaries are measured by our collaborators at the University of Cambridge* using a state-of-the-art equipment.

Magnesium Diboride Superconductor

Dr. Claire Dancer, Dr. Sofia Latif, Mr. Archibald Hardyment, Mr. Ralph Hitchman, Dr. David Hyslop, Dr. Sarah Haigh, Miss Laura Goodsir, Prof. Chris Grovenor

Superconductivity in magnesium diboride was discovered in 2001, with the first powder-in-tube (PIT) wires being produced in the same year. Our research projects in this area are focussed around the correlation of the microstructural properties of magnesium diboride artefacts with their superconducting performance. We have studied the composition and microstructure of PIT wire cores and interfaces, and also the effect of conventional ceramic processing techniques to improve density while retaining low impurity content. This work exploits a wide range of processing and characterisation techniques primarily at Oxford but also collaborating with other institutions.

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