Ph.D. Project: Investigating the interplay of magnetism and superconductivity in thin film devices using advanced neutron, muon and synchrotron techniques

Nanomagnetic devices are present in many high technology systems, a classical example being hard disk drives, where they find use in both the recording media and the magnetoresistive read heads. There is currently an enormous effort in the area of ‘spintronics’, where idealized thin film structures are fabricated to create spin-polarised currents that could find application in a new generation of electronic devices. These devices, such as ‘spin valves’, typically combine juxtaposed layers of magnetic metals and normal metals each of typical thickness a few 10’s of nanometers.

In this project we extend the notion of spintronic devices to include magnetic and superconducting elements. Superconductivity and magnetism are frequently mutually exclusive and in instances where they do coexist in close proximity this often implies some exotic ground state for the system. Our prime motivation is to engineer and detect exotic novel ground states that arise in hybrid thin-film superconducting-magnetic hybrid structure. In the long term a thorough understanding and control of such interactions could lead to exciting new applications. In superconducting spintronic devices, for example, one could envisage a magnetic switch that controls the superconducting wavefunction (amplitude, phase and even the spin pairing) that could be exploited in future electronics and computing applications.

On this project St Andrews is currently collaborating with the University of Leeds, the the University of Bath and the Paul Scherrer Insitute in Switzerland. The collaboration include expertise in sample growth, nanolithography, theory, and advanced characterisation including scanning Hall-probe microscopy and neutron, muon and X-ray techniques. The St Andrews part of the programme is focussed on the use of neutron techniques, the unique low energy muon (LEM) facility at the Paul Scherrer Institute (PSI), Switzerland and advanced Synchrotron techniques, to study the delicate interplay of magnetism and superconductivity in superconducting spin-valve and related systems. This is combined with a strong committment to lab based techniques such as transport and magnetometry. There is however strong potential for mobility and interactions with other members of the collaboration.

The PhD position offers a great opportunity for a highly motivated student to receive outstanding training in advanced techniques at some of the world’s leading central facilities in France, Switzlerland, Germany and the UK.

Ph.D. Project: Studying the Magnetic Properties of Emergent Nanomaterials for Applications in Renewable Energy

We are undertaking an exciting and highly multidisciplinary project to study the magnetic properties and applications of a unique type of nanoparticle produced using a very novel route to synthesis. These materials will find application in a range of very relevant applications such as fuel cells, catalysis and hydrogen production. Many of these materials are magnetic and have magnetic properties that can differ significantly from the bulk form, and the magnetic properties are themselves strongly related to morphology, strain and composition of the nanoparticles. Surfaces decorated with uniformly dispersed catalytically active nanoparticles play a key role in many fields including renewable energy and catalysis. Unlike other nanoparticles that are often used for these types of application, which are used to decorate surfaces in order to functionalise them, the ex-solved nanoparticles we will study in this project emerge from the substrate itself (Figure 1). The collaboration has recently demonstrated that the concept of growing nanoscale particles from perovskite host materials can be achieved for a wide range of metals and even oxides when the nonstoichiometry of the perovskite, and thus its defect chemistry, are carefully tailored. The structure of the nanoparticles is aligned to the chemical structure of the underlying substrate and the particles themselves can be very ordered and also highly strained. Strains approaching 5% have been observed. The extreme strains that are encountered can radically alter the electronic and magnetic properties of the particles, and their strong attachment to the host surfaces makes them highly stable and robust.

The PhD project will involve trying to measure and understand the magnetic properties of these highly novel nanomaterials that have the potential to exhibit really novel properties.  A key part of the project would be the use of SQUID magnetisation to obtain magnetic information, but is also likely to involve more advanced techniques at central facilities too such as muon spin rotation, neutron scattering and X-ray resonant magnetic scattering. We would also expect that involvement in other aspects of characterisation such as electron microscopy would be part of the PhD project.

More advanced aspects of the project could involve relating the spatial correlations of nanoparticles to their inter-particle magnetic interactions and associated phase transitions and is complementary to other work undertaken within the group on realising model artificial nanomaterials involving the controlled introduction  of frustration, disorder and anisotropy [2].

The project is underpinned by a recent EPSRC award of around £4.4M involving the Universities of St Andrews, Newcastle, Ulster, Imperial College and Bath covering many aspects of synthesis, modelling, measurement and application.  The four-year project begins in June 2018 so the studentship would be well aligned to the funded programme, which will also employ a post-doctoral researcher working in the area of magnetic characterisation.

1. D. Neagu, G. Tsekouras, D.N. Miller, H. Menard, J.T.S. Irvine, Nat. Chem . 5 , 916 (2013).
2. Anghinolfi, L., Luetkens, H., Perron, J., Flokstra, M. G., Sendetskyi, O., Suter, A., Prokscha, T., Derlet, P. M., Lee, S. L. & Heyderman, L. J. Nature Communications,  6, 8278 (2015).