Ferromagnetic Oxide & Unconventional Superconductor Heterostructures for Superconducting Spintronics
Lead Research Organisation:
University of Cambridge
Department Name: Materials Science & Metallurgy
Abstract
Superconducting spintronics is the combination of spintronics (the utilisation of electron spin in devices) with superconducting materials. Historically, superconductivity and magnetism were considered incompatible phenomena, but recent developments in nanofabrication have shown that compatibilities and couplings are possible at the interface between superconducting and magnetic materials, and a more complete synergy between the two phenomena is possible through the formation of spin-polarised supercurrents. By depositing ultra-thin films of ferromagnetic and superconducting materials, we can study fundamental physical phenomena occurring at their interfaces, with the aim to control and manipulate spin polarised supercurrents in order to create highly efficient computing devices.
In this PhD, I will create heterostructures using ferromagnetic oxides and high-temperature unconventional superconductors. I will investigate the proximity effects occurring at the interfaces between these materials, and explore the possibility of creating spin polarised supercurrents with unconventional superconductors. A thorough understanding of how to create and manipulate spin polarised supercurrents with unconventional superconductors is critical to developing superconducting spintronic devices which can operate at elevated temperatures.
This project aligns with an EPSRC-JSPS Advanced Materials Grant.
In this PhD, I will create heterostructures using ferromagnetic oxides and high-temperature unconventional superconductors. I will investigate the proximity effects occurring at the interfaces between these materials, and explore the possibility of creating spin polarised supercurrents with unconventional superconductors. A thorough understanding of how to create and manipulate spin polarised supercurrents with unconventional superconductors is critical to developing superconducting spintronic devices which can operate at elevated temperatures.
This project aligns with an EPSRC-JSPS Advanced Materials Grant.
Organisations
Publications
Olde Olthof L
(2021)
Tunable critical field in Rashba superconductor thin films
in Physical Review B
Kimbell G
(2020)
Two-channel anomalous Hall effect in SrRuO 3
in Physical Review Materials
Garcia C
(2020)
Pair suppression caused by mosaic-twist defects in superconducting Sr2RuO4 thin-films prepared using pulsed laser deposition
in Communications Materials
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509620/1 | 01/10/2016 | 30/09/2022 | |||
| 1937217 | Studentship | EP/N509620/1 | 01/10/2017 | 30/09/2021 | Graham Kimbell |
| Description | My studies have focused on the electrical and magnetic properties of epitaxial oxide heterostructures - i.e. nanometer-scale layers of single crystal oxide materials. I have found that there is an interfacial anti-ferromagnetic coupling between two magnetic oxides, SrRuO3 and La0.7Ca0.3MnO3. These two ferromagnets will prefer to align magnetically anti-parallel to each other if they are touching, but are decoupled when a non-magnetic layer is placed between them. This coupling depends on what substrate these layers are grown on. In a different project, there has been recent excitement about a 'topological Hall effect' resulting from 'skyrmions' in ultra-thin SrRuO3 films. Skyrmions are magnetic bubbles which may have important technological uses for memory in computers. I have shown that this effect is likely actually an artifact of two separate magnetic regions, rather than an effect from skyrmions. This work is now published in Physical Review Materials (https://doi.org/10.1103/PhysRevMaterials.4.054414). I am in the final stages of writing a reivew about the 'topological Hall effect' and real-space magnetic imaging as a technique for investigating spin-chirality. These techniques are commonly used in conjunction, but the assumptions for its use are often not valid and this can give misleading results in many structures. A thorough understanding of the limitations of these techniques is vital for making progress in the field. I have also collaborated on projects, growing and characterising yttrium iron garnet films for studies on graphene (https://doi.org/10.1103/PhysRevB.101.241405) and ferromagnetic resonance experiments. I have collaborated on x-ray and magnetic characterisation of Sr2RuO4 thin films, which is an unconventional superconductor with exotic properties (https://doi.org/10.1038/s43246-020-0026-1). These films are some of the first successfully grown by pulsed laser deposition, the growth and characterisation is important for creating devices with this material to understand its unusual superconducting properties. Recently, I have turned my interest towards numerical modelling of superconducting structures. I have collaborated on a theoretical study which found that superconductors can stay superconducting in larger magnetic fields if they are interfaced with heavy metals (https://doi.org/10.1103/PhysRevB.103.L020504). I am now making a numerical model to study superconducting junctions which are too complex to be studied analyically. This work is ongoing. |
| Exploitation Route | This work contributes to the understanding of oxide hetero-structures for use in spintronics and superconducting spintronics. The overarching aim of these fields are to provide faster and more efficient computing devices compared to conventional silicon CMOS computers. Anti-ferromagnetic coupling in SrRuO3/La0.7Ca0.3MnO3 may be used in superconducting spintronic devices, for example unusual magnetic textures can be used to create spin-polarised supercurrents. Showing that the 'topological Hall effect' in SrRuO3 may actually be an artifact of two magnetic regions is an important part of the debate about skyrmions in this material. This material initially seemed very promising for the study and development of skyrmion-based devices, but this may not in fact be the case. Being able to grow Sr2RuO4 thin films rather than bulk single crystals will allow other researchers to create heterostructures using this superconductor, allowing more detailed study into the unusual superconducting properties of this material. |
| Sectors | Digital/Communication/Information Technologies (including Software),Electronics |
| Description | Poster presentation at 6th CAMatNet meeting 2019 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Postgraduate students |
| Results and Impact | Presented a poster on oxide superconducting spintronics at the 6th CAMatNet meeting. I was awarded 1st place in the poster competition, and had interesting and insightful discussions about my work with both researchers and professionals from industry - in particular from Zeiss and AIXTRON. |
| Year(s) Of Engagement Activity | 2019 |
| Description | Poster presentation at Oxide Super Spin conference 2018 in Amalfi, Italy |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Poster presentation on spin mixing at oxide superconductor/ferromagnet interfaces given at the 2018 Oxide Super Spin conference in Amalfi, Italy. The discussion session allowed me to discuss results with academics and gave me useful insight into next steps for my research. |
| Year(s) Of Engagement Activity | 2018 |
| Description | Poster presentation at the 2018 SEFIRA summer school on superconducting electronics, Spain |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Presented a poster on oxide superconducting spintronics at the SEFIRA summer school on superconducting electronics in Minorca, Spain, which sparked some interesting discussion with researchers and academics who were involved in more conventional superconducting electronic circuits. |
| Year(s) Of Engagement Activity | 2018 |
| Description | Presentation in Sapporo, Japan, at the Oxide Super Spin workshop 2018 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Gave a 15 minute presentation on "Triplet conversion in epitaxial oxide heterostructures" to an audience of undergraduates, postgraduate students and academics at the 2018 Oxide Super Spin workshop in Saporro, Japan, including a question and answer session afterwards. |
| Year(s) Of Engagement Activity | 2018 |
| Description | Talk and poster presentation at Oxide Super Spin conference 2019 in Seoul, Korea |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Presented a poster on spin mixing at oxide superconductor/ferromagnet interfaces including a discussion session. Gave a 15 minute talk on the anomalous Hall effect in SrRuO3 thin films, plus a question and answer session which sparked some discussion and started 2 collaborations with international groups. |
| Year(s) Of Engagement Activity | 2019 |