Scattering studies of emergent phenomena at extreme conditions of magnetic field and temperature.

This proposal asks for funding to construct a dilution refrigerator insert for the 17 T cryomagnet previously constructed with EPSRC funds (grant EP/G027161). This cryomagnet is currently being used at neutron scattering facilities throughout the European Economic Area, and is available for use by user groups unconnected with Birmingham, with any necessary support to be provided by us. With the dilution refrigerator insert, the cryomagnet will be able to cover a much larger range of desired experimental materials, without compromising the work that can already be done over the temperature range 2 K to 330 K. At present, this is the largest horizontal magnetic field available for use at any neutron scattering facility. Because small angle neutron scattering is of use to a large number of research communities, being able to move the cryomagnet around from facility to facility maximizes its utility, as it would not be in use full time at any one particular institution.

At present, this equipment has been used, amongst other things, to study the fundamental properties of cuprate superconductors and iron-based superconductors and the effects of magnetic fields on colloidal suspensions of fd virus. We propose to use it to look for anticipated single Landau level effects brought about by high fields in bismuth, as well as flux lines in Pauli-limited superconductors and non-centrosymmetric superconductors, and quantum magnetic ordering.

By extending the temperature range downwards by almost two orders of magnitude, we will be able to extend the research programme into a region where many emergent condensed matter phenomena occur. For instance, heavy fermion superconductors provide fascinating examples of unconventional superconducting phases arising from novel interactions. With the mK region accessible, the cryomagnet is well suited to the critical fields typical for these materials, so that most of their superconducting phase diagrams can be explored. This also makes it easier to investigate the effects of Pauli-limited superconductivity in heavy fermion and pnictide materials.

In addition, this grant will support use of all of the cryomagnet's capabilities by both ourselves and other user groups. As an example, some of our collaborators are very interested in using the cryomagnet to extend studies of magnetic alignment of mesoscopic structures in suspension. We will also be commissioning the cryomagnet at several other facilities, including synchrotron sources, with necessary adaptations to be driven by our collaborators.

This project focuses on knowledge generation by pushing the experimental boundaries of what can be achieved in terms of combined magnetic fields and low temperatures at neutron and x-ray scattering facilities. This will be done by developing and commissioning a dilution refrigerator insert for a 17 T cryomagnet previously funded by EPSRC, lowering the base temperature accessible by nearly two orders of magnitude.

This new capability will be made available to other users through the proposal systems of the various large-scale facilities in the European Economic Area open to applications from UK users. This covers a range of scientific areas, from superconductivity, to magnetic devices, to studies of soft matter, such as viruses. Not all of these topics fall within our own scientific expertise, and so at the moment, we are not able to accurately assess the potential impact of these studies, but by involving as many other scientists we can, we maximize the value-for-money of this EPSRC-funded resource, and its likely impact on a broader scale.

To do this, we shall continue to publicise the cryomagnet and its capabilities to other scientists, by presenting the magnet and results obtained with it at suitable conferences. The facilities where it has been successfully commissioned, and may be used by other users, will be listed on our group website. This has a secondary benefit: by travelling to various large facilities in the European Economic Area, and presenting results obtained with this magnet, built by the UK company Cryogenic Ltd., we provide positive advertising for the company. To date, they have been contacted by two other groups interested in similar magnet systems.

As an example of potential impact outside our own area of scientific interest, one group has proposed a study of NdFeB magnets in high fields, to monitor changes in domain structure as a function of field. The aim of this work is to improve the functionality of the magnets at higher fields by assessing the role of composition and defects on the magnet quality. The results from this will filter through to manufacturers of NdFeB magnets very quickly. To show the breadth of possibilities, another idea that could be tested is that of using large magnetic fields to align mesoscopic materials to form photonic crystals.