New Publication: Electrical Detection of DC Spin Current Propagation Through an Epitaxial Antiferromagnetic NiO Layer

David Newman

Congratulations to third year PGR David Newman, whose paper ‘Electrical Detection of DC Spin Current Propagation Through an Epitaxial Antiferromagnetic NiO Layer’ has recently been published in IEEE Transactions on Magnetics.

David explains this work and the impact of its findings:

Spin currents (net transfer of spin angular momentum) have been suggested as potential successors to charge currents in areas like magnetic data storage. A spin current can be generated by a mechanism known as ‘spin pumping’ whereby a ferromagnetic (FM) layer is excited into resonance and then ‘pumps’ a spin current into an adjacent nonmagnetic (NM) layer. Recently, work has even found that antiferromagnetic (AFM) layers could even be used to amplify the amount of spin current produced.

 

The main issue comes with the difficulty in observing a pure spin current. Current techniques mainly consist of detecting the spin transfer torque exerted on an additional FM layer (AC spin current). Alternatively, the DC spin current can be observed by the transverse charge current generated by a spin current propagating through a heavy metal (like Pt) via the inverse spin Hall effect (ISHE).

 

In our work, we measure the ISHE on a sample with an AFM layer where the AC spin current has already been detected (see separate publication: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.217201) and, with some experimental considerations, extract the DC spin current. By showing AC and DC spin current components can be observed in the same sample, this work provides the pathway to a more complete perspective of spin current propagation through an AFM layer which is important in the development of spintronic technologies in areas such as magnetic data storage.

Elizabeth Martin wins Best Poster Award at 65th Annual Conference on Magnetism and Magnetic Materials (MMM 2020)

Elizabeth with the Best Poster Award Certificate

Congratulations to final year PGR Elizabeth Martin, who won the Best Poster Award at the 65th Annual Conference on Magnetism and Magnetic Materials (MMM 2020) (2nd-6th November 2020). This is an international conference that includes all aspects of fundamental and applied magnetism, which for the first time was held virtually. The conference had over 16000 attendees- including third year CDT PGRs Connor Sait, David Newman, Katie Lewis, Konstantinos Chatzimpaloglou and Oliver Latcham– with ~ 700 different talks and ~370 different posters as well as several different symposia, workshops, and tutorials.

One of our final year students, Elizabeth Martin, presented her research in one of the poster sessions and won a best poster award. Her poster was titled “Investigation of a Coupled Elasto-Magnetic Discs for Low Reynolds Number Pumps”. The presentation was in the format of a 90-second pitch with the poster, which could be viewed at any time throughout the conference on the conference platform, as well as an additional live Q&A session on Zoom.

The virtual format of the conference was a new experience for most of our researchers, they all enjoyed the conference and learnt a lot from the different presentations. However, they do feel that they missed the in-person experience and the chance to meet different researchers from all around the world. On the other hand, think that they have learnt some valuable skills with regards to presenting their work in an online format compared to in-person. The good news for in-person conferences is that according to our researchers their future is safe, they are just having a needed break for now.

Elizabeth says:

The virtual conference was obviously very different to that of the in-person conference, I enjoyed the experience and obviously I’m thrilled to be awarded a best poster award. I did miss the in-person experience and the chance to meet/catch-up with different researchers from all around the world, talking/messaging online is not the same, but this is the way things are at the moment. One of the benefits was that the presentations were in an “on-demand” format, meaning we were able to watch any presentation at any time we wanted because they were pre-recorded (another benefit was that this year none of us experienced jetlag).

The presentations from the conference are available to view on the conference online platform (for registered conference attendees only), until 30th November 2020. Other presenters from University of Exeter included Prof Feodor Ogrin, Elizabeth’s supervisor, and Dr Maciej Dabrowski, David Newman’s supervisor.

 

Elizabeth in avatar form at the conference’s social networking session

David Newman and Kostas Chatzimpaloglou present at the Institute of Physics Current Research in Magnetism 2020: High Frequency Spintronics

Last month, 2nd year PGRs David Newman  and Kostas Chatzimpaloglou both gave contributed talks for the Institute of Physics Current Research in Magnetism 2020: High Frequency Spintronics, which was held virtually.

David Newman

David’s presentation was on “Spin current propagation through an epitaxial antiferromagnetic NiO layer”. In this talk, he demonstrated the use of the inverse spin Hall effect (ISHE) and X-ray Ferromagnetic Resonance (XFMR) measurements to observe a DC and AC spin current respectively propagating through an antiferromagnetic layer in a multilayer sample. This is intended to inform future studies on spin current propagation which is a vital step in the development of spintronic devices.

David says of his talk:

I found it a great experience to present my work as part of a programme filled with the big names in the research field and make more contacts within the community.

 

Kostas’ talk was titled “Time resolved magneto-optical study of spin-orbit torques (SOTs) in ellipsoidal CoFeB/Pt

Kostas Chatzimpalouglou

elements” and focused on results gathered from the development of a magneto-optical Spin Transfer Torque Ferromagnetic Resonance (STT-FMR) technique to explore the magnetization dynamics that arise in these devices in response to DC current excitation.

By comparing with a macrospin model simulation with experimental data, this proves that when DC current is large enough, the DC SOT is observed to act on the magnetization. However, the strong DC Oersted field produces similar features in the resonance to the effect of SOT. Thus, it is required careful fitting to determine the value of SOT.

David Newman chairs session at UK Magnetics Society Student Conference

David Newman

Second year PGR David Newman reently chaired a session at UK Magnetics Society Student Conference where he chaired a session and presented a talk entitled ‘Electrical detection of a DC spin current through an epitaxial antiferromagnetic NiO layer’.

The event was virtually hosted by the UK Magnetics Society to provide a platform for PhD student conference talks that had been cancelled due to the COVID-19 pandemic and also included several talks from academics and industrialists about their experiences in magnetism.

David reports on his experience:

I was responsible for chairing the session on “Nanoscale Magnetics” which featured a broad range of topics from spintronics to materials modelling. Running the session gave me valuable experience in event organisation/management whilst also getting the opportunity to network with other PhD speakers from across the country.

The term “spin currents” refer to the flow of intrinsic spin angular momentum without an accompanying charge transfer (as in a traditional electrical current). In my talk (originally planned for Intermag2020), I showed how the inverse spin Hall effect can be used to transfer a spin current into an electrical current for convenient measurement and applied this to a complex multilayer stack with an antiferromagnetic NiO layer. This work is of particular relevance to magnetic data storage which has turned to spintronic concepts and antiferromagnets for denser magnetic data storage which is more energy-efficient and operates at higher speed.

The conference offers a platform to those students working in magnetics related subjects to talk about their research and work.

New Publication: Coherent Transfer of Spin Angular Momentum by Evanescent Spin Waves within Antiferromagnetic NiO

David Newman

Congratulations to second year PGR David Newman, who has co-authored ‘Coherent Transfer of Spin Angular Momentum by Evanescent Spin Waves within Antiferromagnetic NiO’, recently published in Physical Review Letters. Out of the fourteen co-authors, David is listed fifth. His supervisors Dr. Maciej Dąbrowski and Prof. Robert Hicken are also co-authors.

The publication was also the subject of a Physics Viewpoint article, titled ‘Spin Current in an Antiferromagnet is Coherent’. It has also been featured on the University’s research news as an important breakthrough with the potential to lead to new high speed energy efficient data technology.

March Movie Night: Shaun of The Dead

March 6th saw the latest of the CDT film nights with the theme being “firsts” to mark the first movie night arranged solely by new organisers Emily Glover and David Newman. The winning film was “Shaun of the Dead”, the first of Edgar Wright’s “Cornetto Trilogy”. About 25 of the XM2 PGRs (and a few guests) gathered in Physics SCR to watch the zom-com whilst enjoying a vast offering of free pizza.

CDT Movie Night: Films from the 2010s

The first CDT movie night of the year took place on Friday 24th January, with the theme of films from the 2010s. The winning choice was Scott Pilgrim vs. The World, with 30 PGR attendees.

A big thank you to organisers Ned Taylor and Elizabeth Martin, who are now stepping down to focus on writing up their thesis. The new organisers of the film evening are David Newman and Emily Glover.

L to R: Ned Taylor, Elizabeth Martin, Emily Glover and David Newman

David Newman spends Research Visit at Diamond Light Source

Second year PGR David Newman reports on his latest visit to Diamond Light Source, the UK’s national synchrotron science facility, located at the Harwell Science and Innovation Campus in Oxfordshire.

Between the 9th and 17th of December, I was at the Diamond Light Source in Didcot, near Oxford. The first few days were devoted to a project meeting for the “Picosecond Dynamics of Magnetic Exchange Springs” project where I presented my work on the inverse spin Hall effect to our collaborators from the University of Southampton, University of Oxford and Diamond Light Source. This allowed us to take stock of our current position and plot the best course forward for the respective project partners.

After this I was working on a beamtime at the Diamond Light Source using the X-ray ferromagnetic resonance (XFMR) spectroscopy capabilities of the I10 station. Our aim being to investigate if a Mn spylayer could be used to study an exchange spring locally. This provided a great opportunity to gather vast amounts of data, consolidate understanding with collaborators and gain further experience in running XFMR experiments per my PhD title.

David Newman presents poster at York-Tohoku-Kaiserslautern Research Symposium

On 12th-14th June, first year PGR David Newman attended the York-Tohoku-Kaiserslautern Research Symposium on “New Concept Spintronic Devices”. The symposium is a result of the JSPS Core-to-Core programme that pairs Japanese universities with world-leading universities.

David presented a poster titled”Time-resolved X-ray detected ferromagnetic resonance measurements of a CoFe/NiO/Fe/NiFe multilayer structure”. This involved using X-ray techniques to observe an AC spin current propagating through an antiferrromagnetic NiO layer.

David learnt a lot about how people are incorporating spintronic concepts into devices and novel techniques for studying spin phenomena as well as the conference providing a good opportunity to network.

David Newman presents poster on “Time-resolved X-ray detected ferromagnetic resonance measurements of a CoFe/NiO/Fe/NiFe multilayer structure”

CDT PGRs present at IOP Magnetism 2019 conference

 

Left to right: Elizabeth Martin, Jacob Roth, Emily Glover, Connor Sait, David Newman and Konstantinos Othon Chatzimpaloglou

CDT second year researcher Emily Glover and third year CDT PGR researcher Elizabeth Martin presented at IOP Magnetism 2019 conference, which was held on 8th and 9th April at University of Leeds. Magnetism 2019 is the premier conference organised by the UK and RoI magnetism community. It welcomes and encourages participation from Europe and further afield, and from industry. It follows the highly successful conferences that have been held annually since 2014.

Emily and Elizabeth gave talks entitled “A ferrite-filled cavity resonator for electronic article surveillance on metallic packaging” and “Investigation of Coupled Elasto-Magnetic Pumps for Microfluidic Applications” respectively. This was Emily’s first time presenting at the Magnetism conference series; Elizabeth has presented previously, in 2017 (poster) and 2018 (talk).

First year CDT PGRs Connor Sait, David Newman and Konstantinos Othon Chatzimpaloglou, and third year CDT PGR Jacob Roth, also attended the conference.

More photos below: