Polarized neutron scattering from frustrated magnets

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• Dr. Ross Stewart, STFC
• Friday 29 October 2010, 14:00-15:00
• Physics East 217.

If you have a question about this talk, please contact Elizabeth Blackburn.

Magnetic materials in which the topology of the lattice hampers or even precludes the formation of a long-range ordered (ferro- or antiferro-magnetic) magnetic structure, are said to be frustrated. Such systems display macroscopically degenerate magnetic ground state configurations (i.e. of order N – the number of magnetic ions in the material). This degeneracy may be overcome at low temperatures by higher order terms in the Hamiltonian – such as dipolar interactions or magnetocrystalline anisotropy – and many exotic magnetic states can be realized in these systems. [1] One such is the recently identified “magnetic monopole” phase of the so-called spin-ice pyrochlore systems. [2]

We look at how neutron scattering – and in particular – neutron polarization analysis, can be used to identify and characterise the magnetic ground states of frustrated magnets – in cases where long-range magnetic order is either not-present, or coexistent with disordered phases. Various examples of studies of frustrated magnets using the polarized neutron spectrometer D7 at the Institut Laue-Langevin (Grenoble) [3] will be presented, as well as future perspectives on new instrumentation and techniques.

[1] J N Reimers and A J Berlinsky, Order by disorder in the classical Heisenberg kagome antiferromagnet, Phys. Rev. B 48 (1993) 9539 [2] M J P Gingras, Observing monopoles is a magnetic analogue of ice, Science 326 (2009) 375 [3] J R Stewart, et. al., Disordered materials studied using neutron polarization analysis on the multi-detector spectrometer, D7, J. Appl. Cryst. 42 (2009) 69

This talk is part of the Condensed Matter Physics Seminars series.

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