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Tom Fennell

Tom Fennell's photo
  • Spin ice
  • New frustrated magnets
  • Neutron scattering
 Contact details:
Office: 3P2
Tel: +44 (0)20 7679 9920
Ext: 39920
Fax: +44 (0)20 7679 0595
Email: email.address@ucl.ac.uk

Research Interests
I am interested in frustration, the inability of a system to simultaneously satisfy all pairwise interactions, for example as with three antiferromagnetically coupled spins on a triangular unit.  The systems of main interest for me are the spin ices Ho2Ti2O7 and Dy2Ti2O7, where ever more exotic many body physics is predicted and which is amenable to single crystal neutron scattering studies.  I am also interested in the synthesis, characterization and crystal growth of new frustrated magnets and hope to generalize some of the concepts of our studies of frustration to systems outside magnetism.

Recent Publications

T. Fennell, S.T. Bramwell, D.F. McMorrow, P. Manuel, A.R. Wildes, Pinch Points and Kasteleyn Transitions in Kagome Ice, Nature Physics Vol 3, August 2007. doi:10.1038/nphys632 [PDF file]

This paper describes our recent investigation of a field induced low dimensional phase in spin ice, known as kagome ice.  We were able to observe “pinch point” scattering, a unique feature of ice rule systems; the signature of a tunable critical phase, as originally described by Kasteleyn; and some other mysterious features yet to be explained.

Biography

  • Post-doc (LCN, with Des Mcmorrow, Steve Bramwell and Andrew Wills, 2006-present)
  • Post-doc (European Synchrotron Radiation Facility, France with Veijo Honkimaki, 2005-2006)
  • Post-doc (University of Waterloo, Canada with Prof. Michel Gingras, 2004)
  • PhD (DFRL, Royal Institution/UCL with Steve Bramwell)

Tom Fennell Research ImageResearch
This is the pinch point in kagome ice (the central constriction in the contours). When measuring in reciprocal space, sharpness is associated with long range correlations in direct space and broadness is associated with short range correlations in direct space.  Pinch point scattering is interesting because it combines both sharpness and broadness implying that in the kagome ice state in some directions the spin-spin correlations are very long ranged and in others they are short ranged.