First Experiments on HiFi
12 Jan 2010



HiFi is the new high field muon spectrometer at the ISIS Pulsed Neutron and Muon Source.

​First HiFi data taken for norbornene (a), demonstrating a typical level crossing resonance and (b) longitudinal relaxation data for a cobalt oxalate magnetic compound showing two transitions, one of which is significantly field-dependent.

 This latest addition to the ISIS instrument suite opens up new possibilities for muon studies at ISIS. The instrument has just seen its first successful user experiments, and is now fully available to the ISIS user programme.

HiFi has been built over the past four years. It has an order of magnitude greater applied field than any of the other ISIS muon instruments - up to 5T - extending the range of science that can be done using muons at ISIS.

First users of HiFi have included Dr Alan Drew from Queen Mary University London and Dr Francis Pratt from ISIS.  They have both used HiFi's capabilities to explore organic materials which have interesting electronic or magnetic properties. The instrument is proving very sensitive for such studies, and is performing extremely well.

HiFi was built with funds provided by the UK Science and Technology Facilities Council Facility Development Programme.

Muons are used for studies in areas such as magnetism and superconductivity, charge transport and diffusion, hydrogen behaviour in materials, molecular dynamics, and chemical studies of radicals and reactions.  In many of these areas, muons provide complementary information to neutrons, and many muon users are also regular neutron users.  HiFi extends the range of studies that are possible at ISIS: for example, its large field range improves capabilities for measurement of fluctuations, dynamics and diffusion. There are new opportunities for state preparation and studies of wider regions of magnetic phase diagrams. And it gives access to resonances in molecular systems, normally falling in the 1T-3T range, which provide additional information on structure and dynamics in molecular systems.

First studies on the new instrument have seen explorations of spin scattering processes in organic materials with spintronics applications (A Drew et al, Queen Mary University of London) and studies of organic magnetic systems based on oxalate-bridged transition metal ions (FL Pratt, SJ Blundell et al, ISIS and Oxford University).  In the latter case, for a layered Cobalt oxalate compound a new transition was discovered within the canted antiferromagnetic phase that exists below 22 K. This transition was observed to broaden and shift to higher temperature with applied field, demonstrating  that HiFi can be used to probe magnetic phase diagrams and associated critical fluctuations over a much wider range than was previously available at ISIS.