Steve Bramwell
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- Neutron scattering
- Magnetism
- Statistical Mechanics
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Contact details:
Office: Room 4C3
Tel: +44 (0)20 7679 9963
Ext: 39963
Fax: +44 (0)20 7679 0595
Email:s.t.bramwell ucl.ac.uk
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Research Interest
I design and investigate "model magnets": simple materials that are intended to capture the physics of complex interacting systems. Ideas that have emerged from my work include those of "spin ice", the "BHP" probability distribution and the universal exponent b = 3p2/128 (see refs. 1-3). These ideas have impacted many fields, including condensed matter, turbulence and nanotechnology (see, for example, refs. 4-6).
References:
[1] Bramwell and Gingras, Science, 294 1495 (2001).
[2] Bramwell, Holdsworth and Pinton, Nature, 396 552 (1998).
[3] Bramwell and Holdsworth J. Phys. Condens. Matter, 5 L53 (1993).
[4] Wang et al., Nature 439, 303 (2006).
[5] van Milligan, et al. Phys. Plasmas 12 052507 (2005).
[6] Elmers et al. J. Appl. Phys., 79 4984 (1996).
Other activities
I lecture physical chemistry at UCL's Chemistry Department.
Recent Publications
Phase transitions, partial disorder and multi-k structures in Gd2Ti2O7
This describes some recent neutron scattering work, with Ross Stewart (ILL), Georg Ehlers (Oak Ridge), Jason Gardner (NIST) and Andrew Wills (UCL). In it we establish the magnetic structure (i.e. the ordering pattern of atomic magnetic moments or "spins") in the so-called "frustrated" magnet Gd2Ti2O7. We us a trick, probably for the first time, of distinguishing equivalent ordered magnetic structures by measuring the scattering from disordered spins.
Er2Ti2O7: Evidence of quantum order by disorder in a frustrated antiferromagnet
This paper is headed by Dickon Champion, formerly in our group and now at ISIS. It describes extensive experimental and theoretical work on Er2Ti2O7, in which magnetic order is caused by entropy - so called "order by disorder": an unexpected, but real effect.
Temperature-dependent fluctuations in the two-dimensional XY model
I am primarily an experimentalist, but also have an interest in theoretical statistical mechanics. This recent paper describes the work of Simon Banks, now at Oxford, who studied the probability distribution of magnetization in the "XY model" of magnetism. The distribution is non-Gaussian and has been observed in many complex systems (see also Ref. 2 above).
Biography
- D. Phil Oxford
- Research Scientist at ILL (Grenoble), 1989-94
- Currently Professor of Physical Chemistry and Honorary Professor of Physics at UCL.
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