Generation, Imaging and Control of Novel Coherent Electronic States in Artificial Ferromagnetic-Superconducting Hybrid Metamaterials and Devices

Lead Research Organisation: STFC - Laboratories
Department Name: ISIS Pulsed Neutron & Muon Source

Abstract

Condensed matter physicists are constantly looking for interesting new states of matter and new materials with unique exploitable properties which reflect the complex quantum mechanical interactions of the electrons that bind them together. These electronic properties can sometimes be approximated to the sum of individual electrons moving within the material, such as the electrical conduction of electrons in simple metals or semiconductors like silicon. The properties are on the whole more interesting, however, when an accurate description of the material needs to account for the collective and correlated motion of large numbers of electrons. Such collective physics leads to the familiar ferromagnetic properties of materials like iron and, less familiarly, the phenomenon of superconductivity. In the latter electrons are able to flow through the bulk of a superconducting material without generating heat and extraordinarily high electrical currents become possible. This finds application, for example, in the large superconducting magnets required for MRI body scanners. Magnetism and superconductivity are often antagonistic phenomena, since they involve different arrangements of the spins of electrons. Spin is a quantum property of electrons that gives rise to intrinsic magnetic fields - it can be visualised as a tiny compass needle attached to each electron. In ferromagnetism all the spins point in the same direction, but in conventional superconductivity the electrons form pairs (Cooper pairs) in which the spins point in opposite directions. Ferromagnetism therefore normally destroys these Cooper pairs, and hence superconductivity, by causing their spins to align parallel.
Condensed matter physicists often look for new materials where ferromagnetism and superconductivity coexist, since this can suggest the presence of some exotic new form of superconductivity (or other novel quantum state). One example is spin-triplet superconductivity, in which the spins of a Cooper pair prefer to be aligned parallel rather than antiparallel. One way to try and engender such exotic states of matter is to grow artificial materials by depositing very thin superconducting and ferromagnetic films (a few nm thick) on top of one another. In this way the properties of the final structure can be tuned, sometimes leading it to exhibit behaviours that have never been found in naturally occurring bulk materials. An example of this is a unique kind of spin-triplet (so called odd-frequency) superconductivity that has recently been demonstrated in this type of thin film structure. The production of artificial materials can be taken a step further if one also patterns such thin film materials in the plane of the film using advanced electron beam lithography technology, to produce additional patterns and structures on the nanoscale. Such an approach could lead not only to the discovery of interesting new quantum phases, but could also to useful properties that could be exploited in future technologies, such as quantum computing.
In this project we bring together a team of experts with a diverse range of skills that can grow, pattern, measure and undertake theoretical studies on the type of nanostructured materials discussed above. One particularly novel aspect of our approach is the use of powerful imaging techniques involving neutron, muons, X-rays and bespoke scanning magnetic sensors to gain unique insights into both the basic physics at play in systems exhibiting odd-frequency triplet superconductivity as well as the relation between the detailed magnetic and physical structures and their exotic properties. Although the basic aim of this project is the pursuit of new scientific knowledge, we will be looking for interesting effects and properties that might find future applications.

Publications

10 25 50
 
Description This grant is supporting blue skies curiosity-driven research. In particular we are trying to understand the physics surrounding superconducting correlations in ferromagnet-superconductor hybrid structures, including the generation of triplet (equal spin paired) in non-collinear magnetic systems.
The project is completed and we have made significant progress with regard to our original 10 objectives, with a number of important results either published or currently being prepared for submission to leading physics journals. During the grant period we have established good partnerships with other leading groups in the field (Cambridge, Leiden) and have now produced joint publications with these partners.
The consortium associated with this critical mass grant originally set out an ambitious programme of objectives, and we have made significant progress across all fronts. Below we list 4 examples.
1. Spatially probe the novel spin-triplet state to detect spin-polarisation of Cooper pairs directly and explore new device architectures to enhance the formation and control of spin triplet pairs:
-Experimentally we have placed limits on the size of this effect in the ferromagnetic and superconducting layer using polarized neutron reflectometry (PNR) , XMCD and muon spectroscopy in a range of samples from our own and other leading groups. We developed highly functional spin valve devices based on a Co layer pinned by IrMn. We have also explored magnetic Skyrmion -based structures and the use of epitaxial Er in spin valve devices.

2. Investigate the spin-polarisation of triplet pairs injected into N, conventional S and other materials:
-Extensive progress made in this area with a key publication in the field. We obtained the dramatic finding of a spin -polarization induced in a normal magnetic layer. The role of m=0 or m=+/-1 triplets in this process is not yet completely clear but provides a challenge to theory. The magnitude of the net magnetization in the superconducting layer itself is surprisingly small and these data also provide valuable input for the development of theory.

3. Explore generic aspects of the interaction of magnetic and superconducting order at buried interfaces:
-Using advanced characterisation to understand in detail the structure-function relation of existing spin-triplet devices, extensive data has been collected and is either published or undergoing analysis. We have carried out work both on our own samples and on those from leading groups in the field (Cambridge, Leiden, Hitachi GST), providing useful information on magnetic states and interfacial quality. These have been measured using muons (including Py/Nb, Ho/Nb, Co/Nb spin valves, Er/Nb, Co/Nb bilayers, NiTi/CoPd), PNR (including Ho/Co/Nb, Co/Nb spin valves, NiNb multilayer), and XMCD (including Co/Nb and Fe/Nb spin valves with delta-doped Mn).

4. Improve routes to the reproducible production of exotic hybrid superconducting-magnetic systems over areas large enough to be amenable to a wide range of quantitative techniques:
-We have been highly successful in producing working devices suitable for investigation using a number of techniques systems including XMCD, muons, PNR etc.

We have recently made the exciting discovery of an induced magnetic moment in a non-magnetic metal layer adjacent to a superconducting spin valve structure. Moreover the induced moment can be tuned by varying the relative orientation of the magnetisation in two ferromagnetic layers in the spin valve structure.
Exploitation Route The basic research presented here will form an important component for the development of the field of superconducting spintronics.
Sectors Digital/Communication/Information Technologies (including Software),Electronics

 
Description Our work has generated several media sources picking up the work. News Date News Headline Outlet Name Outlet Type Outlet Country News Attachment Name 09/10/2015 Magnetised gold could change computer technology, research reveals International Business TImes Australia - Online Online, consumer Australia http://www.ibtimes.com.au/magnetised-gold-could-change-computer-technology-research-reveals-1472950 07/10/2015 Magnetised bullion heralds new era of electronics Fresh Ghana.com http://news.vocus.com/?a=22944469161&p=19f&v=1&x=BRtciZWJNd_EQfv31zCo8Q 07/10/2015 Kings of spin scientists have the golden touch Courier (Dundee) - Online, The Online, consumer United Kingdom http://www.thecourier.co.uk/news/local/fife/kings-of-spin-scientists-have-the-golden-touch-1.903787 07/10/2015 Research on magnetising gold could improve computers, say St Andrews University scientists National Online, consumer United Kingdom http://www.thenational.scot/news/research-on-magnetising-gold-could-improve-computers-say-st-andrews-university-scientists.8441 06/10/2015 Scientist discovery 'could make computers faster' scotsman.com Online, consumer United Kingdom http://www.scotsman.com/news/sci-tech/scientist-discovery-could-make-computers-faster-1-3909167 06/10/2015 Scientists reveal next generation spintronics to power faster, smaller computers The Stack https://thestack.com/world/2015/10/06/machiel-flokstra-spintronics-superconductor-magnetised-golf/ 06/10/2015 Magnetised gold heralds new generation of electronics FIRE News http://ftnews.firetrench.com/2015/10/magnetised-gold-heralds-new-generation-of-electronics/ 06/10/2015 Magnetised gold heralds new generation of electronics Aerospace & Defence News http://aerospace.firetrench.com/2015/10/magnetised-gold-heralds-new-generation-of-electronics/ 06/10/2015 Magnetised gold is first step NOODLS Online, trade/industry Italy http://www.noodls.com/viewNoodl/30193155/university-of-bath/spintronics-magnetised-gold-is-first-step 06/10/2015 University of Bath (via noodls) / Magnetised gold heralds new generation of electronics NOODLS Online, trade/industry Italy http://www.noodls.com/viewNoodl/30193150/university-of-bath/magnetised-gold-heralds-new-generation-of-electronics 06/10/2015 Scientists discover 'ground-breaking' magnetic capabilities of gold ITV Network Ltd - Online Online, consumer United Kingdom http://www.itv.com/news/west/2015-10-06/scientists-discover-ground-breaking-magnetic-capabilities-of-gold/ 07/10/2015 Turning gold into spintronics Electronics Weekly http://www.electronicsweekly.com/news/design/university-electronics/turning-gold-into-spintronics-2015-10/ 06/10/2015 Scientists have managed to magnetise gold for the first time ever - and it will change your life Western Daily Press http://www.westerndailypress.co.uk/Scientists-managed-magnetise-gold-time-change/story-27930012-detail/story.html 06/10/2015 Magnetised gold heralds new generation of electronics World News http://article.wn.com/view/2015/10/06/Magnetised_gold_heralds_new_generation_of_electronics_Univer/ 05/10/2015 Superconductor induces magnetism in non-magnetic gold Physics World United Kingdom http://physicsworld.com/cws/article/news/2015/oct/05/superconductor-induces-magnetism-in-non-magnetic-gold 06/10/2015 Superconductivity trained to promote magnetization Phys.org http://phys.org/news/2015-10-superconductivity-magnetization.html
First Year Of Impact 2015
Sector Electronics
Impact Types Cultural,Societal

 
Description SFM Consortium 
Organisation Paul Scherrer Institute
Country Switzerland 
Sector Public 
PI Contribution We provide nanoscale characterisation using, primarily, central facilities. Paper writing
Collaborator Contribution Additional facility characterization and macroscopic measurements. Theoretical interpretation Sample Growth
Impact Scientific literature Post-doctoral training
Start Year 2013
 
Description SFM Consortium 
Organisation Royal Holloway, University of London
Country United Kingdom 
Sector Academic/University 
PI Contribution We provide nanoscale characterisation using, primarily, central facilities. Paper writing
Collaborator Contribution Additional facility characterization and macroscopic measurements. Theoretical interpretation Sample Growth
Impact Scientific literature Post-doctoral training
Start Year 2013
 
Description SFM Consortium 
Organisation University of Bath
Country United Kingdom 
Sector Academic/University 
PI Contribution We provide nanoscale characterisation using, primarily, central facilities. Paper writing
Collaborator Contribution Additional facility characterization and macroscopic measurements. Theoretical interpretation Sample Growth
Impact Scientific literature Post-doctoral training
Start Year 2013
 
Description SFM Consortium 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution We provide nanoscale characterisation using, primarily, central facilities. Paper writing
Collaborator Contribution Additional facility characterization and macroscopic measurements. Theoretical interpretation Sample Growth
Impact Scientific literature Post-doctoral training
Start Year 2013
 
Description SFM Consortium 
Organisation University of St Andrews
Country United Kingdom 
Sector Academic/University 
PI Contribution We provide nanoscale characterisation using, primarily, central facilities. Paper writing
Collaborator Contribution Additional facility characterization and macroscopic measurements. Theoretical interpretation Sample Growth
Impact Scientific literature Post-doctoral training
Start Year 2013
 
Description I'm a scientist get me out of here 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact A national initiative to allow school children to talk with and question research scientists.
Year(s) Of Engagement Activity 2014
URL http://www.imascientist.org.uk
 
Description Indo-UK Science Meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact research talk at an Indo-UK science meeting in Bangalore, India.
Year(s) Of Engagement Activity 2019
 
Description Invited Talk (IFE, Norway) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk at IFE, Norway to discuss superconductivity work.
Year(s) Of Engagement Activity 2015
 
Description Invited Talk (NIST) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk to NIST, Washington DC
Year(s) Of Engagement Activity 2016
 
Description Media Coverage of work 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Press releases following the publication of our work.

News Date News Headline Outlet Name Outlet Type Outlet Country News Attachment Name
09/10/2015 Magnetised gold could change computer technology, research reveals International Business TImes Australia - Online Online, consumer Australia http://www.ibtimes.com.au/magnetised-gold-could-change-computer-technology-research-reveals-1472950

07/10/2015 Magnetised bullion heralds new era of electronics Fresh Ghana.com http://news.vocus.com/?a=22944469161&p=19f&v=1&x=BRtciZWJNd_EQfv31zCo8Q

07/10/2015 Kings of spin scientists have the golden touch Courier (Dundee) - Online, The Online, consumer United Kingdom http://www.thecourier.co.uk/news/local/fife/kings-of-spin-scientists-have-the-golden-touch-1.903787

07/10/2015 Research on magnetising gold could improve computers, say St Andrews University scientists National Online, consumer United Kingdom http://www.thenational.scot/news/research-on-magnetising-gold-could-improve-computers-say-st-andrews-university-scientists.8441

06/10/2015 Scientist discovery 'could make computers faster' scotsman.com Online, consumer United Kingdom http://www.scotsman.com/news/sci-tech/scientist-discovery-could-make-computers-faster-1-3909167

06/10/2015 Scientists reveal next generation spintronics to power faster, smaller computers The Stack https://thestack.com/world/2015/10/06/machiel-flokstra-spintronics-superconductor-magnetised-golf/

06/10/2015 Magnetised gold heralds new generation of electronics FIRE News http://ftnews.firetrench.com/2015/10/magnetised-gold-heralds-new-generation-of-electronics/

06/10/2015 Magnetised gold heralds new generation of electronics Aerospace & Defence News http://aerospace.firetrench.com/2015/10/magnetised-gold-heralds-new-generation-of-electronics/

06/10/2015 Magnetised gold is first step NOODLS Online, trade/industry Italy http://www.noodls.com/viewNoodl/30193155/university-of-bath/spintronics-magnetised-gold-is-first-step

06/10/2015 University of Bath (via noodls) / Magnetised gold heralds new generation of electronics NOODLS Online, trade/industry Italy http://www.noodls.com/viewNoodl/30193150/university-of-bath/magnetised-gold-heralds-new-generation-of-electronics

06/10/2015 Scientists discover 'ground-breaking' magnetic capabilities of gold ITV Network Ltd - Online Online, consumer United Kingdom http://www.itv.com/news/west/2015-10-06/scientists-discover-ground-breaking-magnetic-capabilities-of-gold/

07/10/2015 Turning gold into spintronics Electronics Weekly http://www.electronicsweekly.com/news/design/university-electronics/turning-gold-into-spintronics-2015-10/

06/10/2015 Scientists have managed to magnetise gold for the first time ever - and it will change your life Western Daily Press http://www.westerndailypress.co.uk/Scientists-managed-magnetise-gold-time-change/story-27930012-detail/story.html

06/10/2015 Magnetised gold heralds new generation of electronics World News http://article.wn.com/view/2015/10/06/Magnetised_gold_heralds_new_generation_of_electronics_Univer/

05/10/2015 Superconductor induces magnetism in non-magnetic gold Physics World United Kingdom http://physicsworld.com/cws/article/news/2015/oct/05/superconductor-induces-magnetism-in-non-magnetic-gold

06/10/2015 Superconductivity trained to promote magnetization Phys.org http://phys.org/news/2015-10-superconductivity-magnetization.html
Year(s) Of Engagement Activity 2015
 
Description School Visit (OLV) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Talk to Students about superconductivity
Year(s) Of Engagement Activity 2016
 
Description Symposium on Spin, Coherence, and Topology, Royal Holloway University 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk
Year(s) Of Engagement Activity 2016