Evaluation of spin-orbit torques in thin film magnetic materials and their use in driving (PhD in Physics) Ref: 3395

About the award

This project is subject to funding decision by EPSRC:

We are currently awaiting a decision from EPSRC regarding an application for a Centre for Doctoral Training in Functional and Meta- Materials (2019-2027) which will build on our expertise in Doctoral Training gained through the CDT in Metamaterials (XM²) since 2014.  A funding decision is expected by January 2019.
The successful applicant will join the new CDT programme if Exeter succeeds in its bid.

For eligible students the 4 year studentship (value approx. £94,000) will cover UK/EU tuition fees, plus an annual tax-free stipend at the UKRI national minimum doctoral level (£14,777 for 2018) plus £250 per year), or pro rata for part-time study, plus a Research and Training Support Grant (RTSG) of £13,000. Tuition fees and RTSG only for international students.

XM² now has over 80 post graduate researchers.  Its aim is to undertake world-leading research, while training scientists and engineers with the relevant research skills and knowledge, and professional attributes for industry and academia.

Please visit www.exeter.ac.uk/metamaterials for more information about the current CDT and an indication of what to expect.

This studentship will be based on the Streatham Campus in Exeter. 

Joint supervisors: Prof R J Hicken, Dr P S Keatley

External supervisor: Prof K L Livesey (University of Colorado, UCCS)

Statement of Research

Spin orbit torques (SOTs) result from the spin Hall and Rashba effects within multilayered thin film magnetic materials.  An injected charge current generates a spin current that can transfer angular momentum to local magnetic moments, thereby exerting a torque upon them. hin the Spintronics, Magnonics and Magnetic Materials theme.  SOTs have the advantage that charge current may be passed within the plane of the film, rather than through a delicate tunnel barrier, so that larger current densities, sufficient to change the magnetic state of the sample, may be used.  It is expected that SOTs will be exploited in future generations of magnetic random access memory (MRAM) device, and within new data storage and processing paradigms that harness topological structures such as domain walls vortices and skyrmions.

The PhD project is aligned with 2 EPSRC grants [1,2] that support experienced researchers who will be happy to share their expertise.  The first grant uses time resolved scanning Kerr microscopy to detect the magnetization dynamics detected by spin orbit torques within thin film magnetic materials formed into Hall bars and spin transfer oscillators.  The second uses time resolved optical measurements to study magnetization dynamics in a wide range of magnetic structures and devices.  The motion of topological structures within such materials is a major theme within the EXTREMAG project.

Existing measurement methods rely on magnetoresistive response to characterise spin-orbit torques.  However this approach does not sense the magnetization directly, provides a null response in certain geometries of interest, and lacks spatial resolution.  Direct optical detection of the magnetization overcomes all of these difficulties and, together with the detection of the resulting dynamics in candidate MRAM and spin transfer oscillator devices, is the goal of the first EPSRC grant [1].  The proposed PhD project is intended to provide the theory and modelling needed to extract the values of the torques reliably and understand how they induce dynamic response within devices where the magnetization undergoes quasi-uniform precession.  This theory will then be extended to more complicated topological objects such as skyrmions.  Specifically, the means by which skyrmions move within thin films will be explored, with particular focus upon whether the internal dynamics of skyrmions affect their translational motion and interaction with defects and pinning sites, such as those found at the edges of nanowires that are used to guide their motion.

[1] “Optical detection of magnetisation dynamics induced by spin-orbit torques”, EP/P008550/1.
[2] “EXTREMAG: an Exeter-based Time Resolved Magnetism Facility”, EP/R008809/1.

About us

Exeter has a well-established and strong track record in functional materials and metamaterials research, spanning a unique mix of interests in our focus areas:

  •     Acoustic, Phononic and Fluidic Metamaterials
  •     Microwave and RF Metamaterials and Devices
  •     Nanocomposites and Manufacturing
  •     Photonic and Plasmonic Materials
  •     Soft Matter, Biomaterials and Sensors
  •     Spintronics, Magnonics and Magnetic Materials
  •     Theory and Modelling to drive Targeted Material and Device Design
  •     Two Dimensional Electronic and Photonic Materials

Exeter is amongst the top 150 universities worldwide according to the Times Higher Education World University Rankings, the most influential global league table.
Functional Materials (from fundamentals to manufacturing) is one of 5 key themes supported by the UoE as part of its £320 million Science Strategy investing in staff and facilities. This theme has benefitted from the appointment of 23 new academics (including 7 full professors) along with £20m of investment in research infrastructure (including 3 new electronics/photonics clean-rooms, a graphene engineering laboratory, a nano-functional materials fabrication suite, a materials characterisation suite).

This is in parallel to significant external capital investment in our research including over £2m of equipment funding from the EPSRC/HEFCE SIA award (Exeter-Bath Centre for Graphene Science), the £2.6m ERDF-EADS funded Exeter Centre for Additive Layer Manufacture (CALM); £1.1, for Exeter’s EPSRC Time-Resolved Magnetism Facility; £1.2m for equipment funding from the EPSRC Graphene Engineering Call. Such investments ensure that we have, in-house, all the state-of-the-art materials, fabrication and characterisation facilities required by our PGRs.

Our research and PhD training experience, expertise, facilities and network makes the University of Exeter one of the very best places to pursue postgraduate and early career research.

How to apply

Application criteria

During the application process you will need to upload the documents listed below. Please prepare these before starting the application process.

  • An academic CV;
  • A cover letter outlining your research interests in general, the title of the project you are applying for;
  • A Personal Statement consisting of two parts*:
  1.     Describe a) why you would like to study for a PhD, b) why you would like to focus on this particular topic, c) any relevant expertise and d) your future career ambitions;

  2.     Describe the qualities that you believe will make you a great researcher (in particular as part of a team).

  • Degree transcript(s) giving information about the qualification awarded, the modules taken during the study period, and the marks for each module taken;

You will be asked to provide the contact details of two academic referees.

* We foster creativity and utilisation of individual strengths. Applicants are encouraged to provide evidence to support their statements. This might include conventional written documents (e.g. examples of work), but we also encourage alternatives such as audio or video recordings, websites, programming etc. Please ensure to include accessible links to such files in an appropriately named document as part of the upload process.


Application procedure

Shortlisting and interviews

Applications will be reviewed by at least two academic members of staff.

Candidates will be short-listed against a set of agreed criteria to ensure quality while maintaining diversity. Failure to include all the the elements listed above may result in rejection.

The essential criteria:

  • Undergraduate degree in a relevant discipline (minimum 2:1);
  • Vision and motivation (for research & professional development);
  • Evidence of the ability to work collaboratively and to engage in a diverse community;
  • Evidence of excellent written and oral skills in English.

The highest quality candidates will also be able to demonstrate one of more of the following:

  • Specialist knowledge about one or more of the 8 research areas listed above;
  • Training in research methodology (e.g. undergraduate research projects);
  • Research outputs (e.g. papers) and/or other indicators of academic excellence (e.g. awards).

Shortlisted candidates will be invited to an entry interview to assess whether they are suited to the CDT concept. The panel will normally consist of 3 people, including members of the CDT's Strategic Leadership Team and a current postgraduate researchers or post-doc in Physics or Engineering. If the applicant is successful, a second interview will take place to assess academic skills and fit to the project by the project supervisors.

Interviews are expected to start in the second half of January 2019.

Please email metamaterials@exeter.ac.uk if you have any queries about this process.

Summary

Application deadline:30th April 2019
Number of awards:1
Value:Approx. £94,000 for 48 months (pro-rata for part-time study): covers UK/EU tuition fees, annual tax-free stipend at UKRI minimum doctoral level (£14,777 for 2018) plus £250 per year, plus £13,000 RTSG. International students: fees & RTSG only.
Duration of award:per year
Contact: Prof. Alastair Hibbins (Admissions Tutor) metamaterials@exeter.ac.uk