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Miller JD, Ullstad FH, Trodahl HJ, Ruck BJ, Natali F. Vertical transport and tunnelling in rare-earth nitride heterostructures. NANOTECHNOLOGY 2020; 31:235202. [PMID: 32078999 DOI: 10.1088/1361-6528/ab7886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report an investigation of the ferromagnetic semiconductor rare earth nitrides (RENs) for their potential for cryogenic-temperature electronics and spintronics applications. We have identified ohmic contacts suitable for the device structures that demand electron transport through interface layers, and grown REN/insulator/REN heterostructures that display tunnelling characteristics, an enormous 400% tunneling magnetoresistance and a hysteresis promising their exploitation in non-volatile magnetic random access memory.
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Affiliation(s)
- Jackson D Miller
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
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Caruso R, Giovanna Ahmad H, Pal A, Piero Pepe G, Massarotti D, Blamire MG, Tafuri F. Low temperature characterization of high efficiency spin-filter Josephson junctions. EPJ WEB OF CONFERENCES 2020. [DOI: 10.1051/epjconf/202023305007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The interplay between superconducting and ferromagnetic order pa¬rameters in S/F interfaces gives rise to a wide range of peculiar properties with applications in high-efficiency computation and in the emerging field of super¬conducting spintronics. In NbN/GdN/NbN Josephson junctions, GdN barriers give unique properties due to the double insulting and ferromagnetic nature of the material, as demonstrated in previous works. Here we focus on tunneling spectroscopy of these junctions down to 0.3 K when changing the barrier thick¬ness, which contributes to complete a consistent picture on the physics of these junctions and supports the previous indications of equal-spin Cooper pairs con¬tributing to the total supercurrent of the devices.
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Caruso R, Massarotti D, Campagnano G, Pal A, Ahmad HG, Lucignano P, Eschrig M, Blamire MG, Tafuri F. Tuning of Magnetic Activity in Spin-Filter Josephson Junctions Towards Spin-Triplet Transport. PHYSICAL REVIEW LETTERS 2019; 122:047002. [PMID: 30768353 DOI: 10.1103/physrevlett.122.047002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Indexed: 06/09/2023]
Abstract
The study of superconductor-ferromagnet interfaces has generated great interest in the last decades, leading to the observation of spin-aligned triplet supercurrents and 0-π transitions in Josephson junctions where two superconductors are separated by an itinerant ferromagnet. Recently, spin-filter Josephson junctions with ferromagnetic barriers have shown unique transport properties, when compared to standard metallic ferromagnetic junctions, due to the intrinsically nondissipative nature of the tunneling process. Here we present the first extensive characterization of spin polarized Josephson junctions down to 0.3 K, and the first evidence of an incomplete 0-π transition in highly spin polarized tunnel ferromagnetic junctions. Experimental data are consistent with a progressive enhancement of the magnetic activity with the increase of the barrier thickness, as neatly captured by the simplest theoretical approach including a nonuniform exchange field. For very long junctions, unconventional magnetic activity of the barrier points to the presence of spin-triplet correlations.
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Affiliation(s)
- R Caruso
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- SeeQC-eu, via dei Due Macelli 66, I-00187 Roma, Italy
| | - D Massarotti
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- Dipartimento di Ingegneria Elettrica e delle Tecnologie dell'Informazione, Università degli Studi di Napoli Federico II, via Claudio, I-80125 Napoli, Italy
| | - G Campagnano
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
| | - A Pal
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - H G Ahmad
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
| | - P Lucignano
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
| | - M Eschrig
- Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
| | - M G Blamire
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - F Tafuri
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
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Mesoraca S, Knudde S, Leitao DC, Cardoso S, Blamire MG. All-spinel oxide Josephson junctions for high-efficiency spin filtering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:015804. [PMID: 29135466 DOI: 10.1088/1361-648x/aa9a9d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Obtaining high efficiency spin filtering at room temperature using spinel ferromagnetic tunnel barriers has been hampered by the formation of antiphase boundaries due to their difference in lattice parameters between barrier and electrodes. In this work we demonstrate the use of LiTi2O4 thin films as electrodes in an all-spinel oxide CoFe2O4-based spin filter devices. These structures show nearly perfect epitaxy maintained throughout the structure and so minimise the potential for APBs formation. The LiTi2O4 in these devices is superconducting and so measurements at low temperature have been used to explore details of the tunnelling and Josephson junction behaviour.
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Affiliation(s)
- S Mesoraca
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
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Pal A, Ouassou JA, Eschrig M, Linder J, Blamire MG. Spectroscopic evidence of odd frequency superconducting order. Sci Rep 2017; 7:40604. [PMID: 28106102 PMCID: PMC5247762 DOI: 10.1038/srep40604] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 11/30/2016] [Indexed: 12/03/2022] Open
Abstract
Spin filter superconducting S/I/N tunnel junctions (NbN/GdN/TiN) show a robust and pronounced Zero Bias Conductance Peak (ZBCP) at low temperatures, the magnitude of which is several times the normal state conductance of the junction. Such a conductance anomaly is representative of unconventional superconductivity and is interpreted as a direct signature of an odd frequency superconducting order.
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Affiliation(s)
- Avradeep Pal
- Department of Materials Science, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - J. A. Ouassou
- Department of Physics, NTNU, Norwegian University, N-7491 Trondheim, Norway
| | - M. Eschrig
- SEPnet and Hubbard Theory Consortium, Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
| | - J. Linder
- Department of Physics, NTNU, Norwegian University, N-7491 Trondheim, Norway
| | - M. G. Blamire
- Department of Materials Science, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
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Massarotti D, Pal A, Rotoli G, Longobardi L, Blamire MG, Tafuri F. Macroscopic quantum tunnelling in spin filter ferromagnetic Josephson junctions. Nat Commun 2015; 6:7376. [PMID: 26054495 PMCID: PMC4468849 DOI: 10.1038/ncomms8376] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 05/01/2015] [Indexed: 11/13/2022] Open
Abstract
The interfacial coupling of two materials with different ordered phases, such as a superconductor (S) and a ferromagnet (F), is driving new fundamental physics and innovative applications. For example, the creation of spin-filter Josephson junctions and the demonstration of triplet supercurrents have suggested the potential of a dissipationless version of spintronics based on unconventional superconductivity. Here we demonstrate evidence for active quantum applications of S-F-S junctions, through the observation of macroscopic quantum tunnelling in Josephson junctions with GdN ferromagnetic insulator barriers. We show a clear transition from thermal to quantum regime at a crossover temperature of about 100 mK at zero magnetic field in junctions, which present clear signatures of unconventional superconductivity. Following previous demonstration of passive S-F-S phase shifters in a phase qubit, our result paves the way to the active use of spin filter Josephson systems in quantum hybrid circuits.
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Affiliation(s)
- D. Massarotti
- Dipartimento di Fisica, Università degli Studi di Napoli ‘Federico II', Monte S.Angelo, I-80126 Napoli, Italy
- CNR-SPIN UOS Napoli, Monte S.Angelo-via Cinthia, I-80126 Napoli, Italy
| | - A. Pal
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - G. Rotoli
- Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università degli Studi di Napoli, I-81031 Aversa (Ce), Italy
| | - L. Longobardi
- Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università degli Studi di Napoli, I-81031 Aversa (Ce), Italy
- American Physical Society, 1 Research Road, Ridge, New York 11961, USA
| | - M. G. Blamire
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - F. Tafuri
- CNR-SPIN UOS Napoli, Monte S.Angelo-via Cinthia, I-80126 Napoli, Italy
- Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università degli Studi di Napoli, I-81031 Aversa (Ce), Italy
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Prasad B, Zhang W, Jian J, Wang H, Blamire MG. Strongly bias-dependent tunnel magnetoresistance in manganite spin filter tunnel junctions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:3079-3084. [PMID: 25845706 DOI: 10.1002/adma.201405147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 03/12/2015] [Indexed: 06/04/2023]
Abstract
A highly unconventional bias-dependent tunnel magnetoresistance (TMR) response is observed in Sm0.75 Sr0.25 MnO3 -based nanopillar spin filter tunnel junctions (SFTJs) with two different behaviors in two different thickness regimes of the barrier layer. Thinner barrier devices exhibit conventional SFTJ behaviors; however, for larger barrier thicknesses, the TMR-bias dependence is more complex and reverses sign at higher bias.
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Affiliation(s)
- Bhagwati Prasad
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS, UK
| | - Wenrui Zhang
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, 77843-3128, USA
| | - Jie Jian
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, 77843-3128, USA
| | - Haiyan Wang
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, 77843-3128, USA
| | - Mark G Blamire
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS, UK
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Miao GX, Moodera JS. Spin manipulation with magnetic semiconductor barriers. Phys Chem Chem Phys 2015; 17:751-61. [DOI: 10.1039/c4cp04599h] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Magnetic semiconductors with unique spin-filtering property and the ability to create excessive internal magnetic fields can open myriads of new phenomena.
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Affiliation(s)
- Guo-Xing Miao
- Institute for Quantum
- Computing and Department of Electrical and Computer Engineering
- University of Waterloo
- Waterloo
- Canada
| | - Jagadeesh S. Moodera
- Francis Bitter Magnet Laboratory
- Massachusetts Institute of Technology
- Cambridge
- USA
- Department of Physics
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Blamire MG, Robinson JWA. The interface between superconductivity and magnetism: understanding and device prospects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:453201. [PMID: 25318455 DOI: 10.1088/0953-8984/26/45/453201] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Ferromagnetism and conventional singlet superconductivity can be regarded as competing ordering phenomena. A considerable body of theoretical work over the past twenty years has predicted that at interfaces between the two systems competition or coupling between superconducting and magnetic phenomena are possible. Despite the very short lengthscales over which some of the phenomena exist, many of these predictions have been experimentally realized. The aim of this topical review is to provide an overview of the experimental position and to discuss the potential developments and applications of existing results.
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Affiliation(s)
- M G Blamire
- Department of Materials Science, University of Cambridge, 27 Charles Babbage Road, Cambridge, UK
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Prasad B, Egilmez M, Schoofs F, Fix T, Vickers ME, Zhang W, Jian J, Wang H, Blamire MG. Nanopillar spin filter tunnel junctions with manganite barriers. NANO LETTERS 2014; 14:2789-2793. [PMID: 24742375 DOI: 10.1021/nl500798b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The potential of a manganite ferromagnetic insulator in the field of spin-filtering has been demonstrated. For this, an ultrathin film of Sm0.75Sr0.25MnO3 is integrated as a barrier in an epitaxial oxide nanopillar tunnel junction and a high spin polarization of up to 75% at 5 K has been achieved. A large zero-bias anomaly observed in the dynamic conductance at low temperatures is explained in terms of the Kondo scattering model. In addition, a decrease in spin polarization at low bias and hysteretic magneto-resistance at low temperatures are reported. The results open up new possibilities for spin-electronics and suggest exploration of other manganites-based materials for the room temperature spin-filter applications.
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Affiliation(s)
- Bhagwati Prasad
- Department of Materials Science and Metallurgy, University of Cambridge , 27 Charles Babbage Road, Cambridge, CB3 0FS, U.K
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Pal A, Barber Z, Robinson J, Blamire M. Pure second harmonic current-phase relation in spin-filter Josephson junctions. Nat Commun 2014; 5:3340. [DOI: 10.1038/ncomms4340] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Accepted: 01/29/2014] [Indexed: 11/09/2022] Open
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