To provide even greater data densities on magnetic hard disk drives (HDD) not only requires writing of smaller bits but also the ability to read these small bits. To make this possible requires the reduction in the width of the conventional tunnelling magnetoresistance (TMR) sensor. A conventional TMR sensor is comprised of an antiferromagnetic (AFM) layer that pins a ferromagnetic layers which is separated by an insulting tunnel barrier from the ‘free’ ferromagnetic layer. The pinned and free layers act as a spin filter to current, which varies the resistance of the junction as the free layer responds to an external magnetic field.
Tunnel anisotropic magnetoresistance (TAMR) appears due to change of the density of states at the Fermi level when magnetic (sub)lattice rotates with respect to the crystal field. This is seen in materials with strong spin-orbit (SO) interactions are required e.g. CoPt (Phys. Rev. Letts 100, 087204 (2008)).
A very large 160% TAMR was seen in an IrMn AFM based magnetic tunnel junction (MTJ) but measured at low temperatures (Nature Mat. 10, 347 (2011)). If this can be raised to room temperatures, a reader with only one magnetic electrode can be created, removing the need for the second ferromagnetic electrode and thereby reducing the reader width.
In this PhD the aim is to investigate TAMR junctions with the objective of AFM optimisation and / or new AFM materials to demonstrate high TAMR at room temperature.
To start, TAMR based MTJs will be investigated with focus on growth of highly textured / single crystalline AFM on top of a ferromagnet followed by growth of MTJs on top of the AFM, with a non-magnetic top electrode. The new intermetallic AFM alloys like Mn2Au will then be explored, particular there texturing and their switching by electrical current. This will then lead on to the creation of these intermetallic MTJs targeting optimised TAMR room temperature performance.
In the project you will get training and experience in thin film deposition, structural and magnetic characterisation and transport measurements over wide temperature range allied to lithographic microfabrication of MTJs. Some of this will involve use and exposure device fabrication in the Seagate Technology facility. In addition wider project management and innovation training will be emphasised. You will join a team of people working on the programme supported by Seagate Technology and the Royal Academy of Engineering investigating magnetic materials and the closely related EPSRC CDT in Photonic Integration & Advanced Data Storage. You’ll be assigned an industry mentor at Seagate Technology and will spend time there regularly interacting with their R&D staff, understanding the boarder context, and implementation of your results in an real industry context.
How to apply: Applications should be made through the QUB application portal at the following link: https://dap.qub.ac.uk/portal/user/u_login.php
. Please, ensure that your application is directed to the School of Mathematics and Physics.
Deadline for applications is: 28 February 2019. Interviews to take place shortly thereafter. Your application must include a CV and a presentation letter (max 1 page on your motivation to apply) – these can be attached as the proposal.
Full Award Eligibility: To be eligible to apply for a fully-funded EPSRC studentship, you must:
be a UK or EU citizen or a non-EU citizen with permanent settled status in the UK (known as ‘indefinite leave to remain’)
have been ordinarily resident in the UK for at least 3 years prior to the start of the studentship
Fees Only Award Eligibility: EU citizens who will not have lived in the UK for the last 3 years preceding the start of the studentship would normally be eligible for a Fees Only Award. The Fee Award does not include a stipend, therefore funding to cover living costs for at least 3 years will need to be sought from another source.
For further guidance regarding please refer to Postgraduate Studentships Terms and Conditions and the regulations at: https://www.economy-ni.gov.uk/publications/student-finance-postgraduate-studentships-terms-and-conditions http://www.qub.ac.uk/Study/PostgraduateStudy/TuitionFees/Postgraduatefeestatus/
Funding: For UK domiciled students the value of an award includes the cost of approved fees as well as maintenance support. In academic year 2018-2019 the basic rate of maintenance support for a Research Studentship was £14,777 per annum.
To be eligible, candidates should hold at least a 2.1 BSc (or equivalent) in Physics or related subject.
For an informal discussion of the project contact Prof Robert Bowman at [email protected]