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Satchell N, Gupta S, Maheshwari M, Shepley PM, Rogers M, Cespedes O, Burnell G. Thin film epitaxial [111] Co[Formula: see text]Pt[Formula: see text]: structure, magnetisation, and spin polarisation. Sci Rep 2023; 13:12468. [PMID: 37528131 PMCID: PMC10394051 DOI: 10.1038/s41598-023-37825-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 06/28/2023] [Indexed: 08/03/2023] Open
Abstract
Ferromagnetic films with perpendicular magnetic anisotropy are of interest in spintronics and superconducting spintronics. Perpendicular magnetic anisotropy can be achieved in thin ferromagnetic multilayer structures, when the anisotropy is driven by carefully engineered interfaces. Devices with multiple interfaces are disadvantageous for our application in superconducting spintronics, where the current perpendicular to plane is affected by the interfaces. Robust intrinsic PMA can be achieved in certain Co[Formula: see text]Pt[Formula: see text] alloys and compounds at any thickness, without increasing the number of interfaces. Here, we grow equiatomic Co[Formula: see text]Pt[Formula: see text] and report a comprehensive study on the structural, magnetic, and spin-polarisation properties in the [Formula: see text] and [Formula: see text] ordered compounds. Primarily, interest in Co[Formula: see text]Pt[Formula: see text] has been in the [Formula: see text] crystal structure, where layers of Pt and Co are stacked alternately in the [100] direction. There has been less work on [Formula: see text] crystal structure, where the stacking is in the [111] direction. For the latter [Formula: see text] crystal structure, we find magnetic anisotropy perpendicular to the film plane. For the former [Formula: see text] crystal structure, the magnetic anisotropy is perpendicular to the [100] plane, which is neither in-plane or out-of-plane in our samples. We obtain a value for the ballistic spin polarisation of the [Formula: see text] and [Formula: see text] Co[Formula: see text]Pt[Formula: see text] to be [Formula: see text].
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Affiliation(s)
- N. Satchell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - S. Gupta
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - M. Maheshwari
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - P. M. Shepley
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - M. Rogers
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - O. Cespedes
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - G. Burnell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
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Satchell N, Mitchell T, Shepley PM, Darwin E, Hickey BJ, Burnell G. Pt and CoB trilayer Josephson [Formula: see text] junctions with perpendicular magnetic anisotropy. Sci Rep 2021; 11:11173. [PMID: 34045523 PMCID: PMC8159980 DOI: 10.1038/s41598-021-90432-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 04/05/2021] [Indexed: 11/13/2022] Open
Abstract
We report on the electrical transport properties of Nb based Josephson junctions with Pt/Co[Formula: see text]B[Formula: see text]/Pt ferromagnetic barriers. The barriers exhibit perpendicular magnetic anisotropy, which has the main advantage for potential applications over magnetisation in-plane systems of not affecting the Fraunhofer response of the junction. In addition, we report that there is no magnetic dead layer at the Pt/Co[Formula: see text]B[Formula: see text] interfaces, allowing us to study barriers with ultra-thin Co[Formula: see text]B[Formula: see text]. In the junctions, we observe that the magnitude of the critical current oscillates with increasing thickness of the Co[Formula: see text]B[Formula: see text] strong ferromagnetic alloy layer. The oscillations are attributed to the ground state phase difference across the junctions being modified from zero to [Formula: see text]. The multiple oscillations in the thickness range [Formula: see text] nm suggests that we have access to the first zero-[Formula: see text] and [Formula: see text]-zero phase transitions. Our results fuel the development of low-temperature memory devices based on ferromagnetic Josephson junctions.
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Affiliation(s)
- N. Satchell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - T. Mitchell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - P. M. Shepley
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - E. Darwin
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - B. J. Hickey
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
| | - G. Burnell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT UK
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Shepley PM, Burnell G, Moore TA. Domain wall energy and strain in Pt/Co/Ir thin films on piezoelectric transducers. J Phys Condens Matter 2018; 30:344002. [PMID: 30063029 DOI: 10.1088/1361-648x/aad3a2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We study the energy and creep velocity of magnetic domain walls in perpendicularly magnetised Pt/Co/Ir thin films under strain. We find that the enhancement of domain wall creep velocity under strain from piezoelectric transducers is largest in films with the thinnest Co layers (0.56 nm), in which the strain causes the smallest relative change in perpendicular magnetic anisotropy and the largest relative change in domain wall creep velocity. We show how domain wall energy is predictive of the sensitivity of domain wall creep velocity to changes in strain, and thus provide a route to designing magnetic thin film systems for optimum strain control.
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Zeissler K, Mruczkiewicz M, Finizio S, Raabe J, Shepley PM, Sadovnikov AV, Nikitov SA, Fallon K, McFadzean S, McVitie S, Moore TA, Burnell G, Marrows CH. Pinning and hysteresis in the field dependent diameter evolution of skyrmions in Pt/Co/Ir superlattice stacks. Sci Rep 2017; 7:15125. [PMID: 29123144 PMCID: PMC5680206 DOI: 10.1038/s41598-017-15262-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 10/17/2017] [Indexed: 11/09/2022] Open
Abstract
We have imaged Néel skyrmion bubbles in perpendicularly magnetised polycrystalline multilayers patterned into 1 µm diameter dots, using scanning transmission x-ray microscopy. The skyrmion bubbles can be nucleated by the application of an external magnetic field and are stable at zero field with a diameter of 260 nm. Applying an out of plane field that opposes the magnetisation of the skyrmion bubble core moment applies pressure to the bubble and gradually compresses it to a diameter of approximately 100 nm. On removing the field the skyrmion bubble returns to its original diameter via a hysteretic pathway where most of the expansion occurs in a single abrupt step. This contradicts analytical models of homogeneous materials in which the skyrmion compression and expansion are reversible. Micromagnetic simulations incorporating disorder can explain this behaviour using an effective thickness modulation between 10 nm grains.
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Affiliation(s)
- K Zeissler
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.
| | - M Mruczkiewicz
- Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04, Bratislava, Slovak Republic
| | - S Finizio
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen, Switzerland
| | - J Raabe
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen, Switzerland
| | - P M Shepley
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - A V Sadovnikov
- Laboratory "Metamaterials", Saratov State University, Saratov, 410012, Russia.,Kotel'nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow, 125009, Russia
| | - S A Nikitov
- Laboratory "Metamaterials", Saratov State University, Saratov, 410012, Russia.,Kotel'nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow, 125009, Russia
| | - K Fallon
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - S McFadzean
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - S McVitie
- School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - T A Moore
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - G Burnell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - C H Marrows
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
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Galloway JM, Bird SM, Talbot JE, Shepley PM, Bradley RC, El-Zubir O, Allwood DA, Leggett GJ, Miles JJ, Staniland SS, Critchley K. Nano- and micro-patterning biotemplated magnetic CoPt arrays. Nanoscale 2016; 8:11738-11747. [PMID: 27221982 DOI: 10.1039/c6nr03330j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Patterned thin-films of magnetic nanoparticles (MNPs) can be used to make: surfaces for manipulating and sorting cells, sensors, 2D spin-ices and high-density data storage devices. Conventional manufacture of patterned magnetic thin-films is not environmentally friendly because it uses high temperatures (hundreds of degrees Celsius) and high vacuum, which requires expensive specialised equipment. To tackle these issues, we have taken inspiration from nature to create environmentally friendly patterns of ferromagnetic CoPt using a biotemplating peptide under mild conditions and simple apparatus. Nano-patterning via interference lithography (IL) and micro-patterning using micro-contact printing (μCP) were used to create a peptide resistant mask onto a gold surface under ambient conditions. We redesigned a biotemplating peptide (CGSGKTHEIHSPLLHK) to self-assemble onto gold surfaces, and mineralised the patterns with CoPt at 18 °C in water. Ferromagnetic CoPt is biotemplated by the immobilised peptides, and the patterned MNPs maintain stable magnetic domains. This bioinspired study offers an ecological route towards developing biotemplated magnetic thin-films for use in applications such as sensing, cell manipulation and data storage.
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Affiliation(s)
- J M Galloway
- School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK and School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - S M Bird
- Department of Chemistry, University of Sheffield, Dainton Building, Brook Hill, S3 7HF, UK
| | - J E Talbot
- School of Computer Science, University of Manchester, Kilburn Building, Oxford Road, Manchester, M13 9PL, UK
| | - P M Shepley
- School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - R C Bradley
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Maplin Street, Sheffield, S1 3JD, UK
| | - O El-Zubir
- Department of Chemistry, University of Sheffield, Dainton Building, Brook Hill, S3 7HF, UK and School of Chemistry, University of Newcastle, Chemical Nanoscience Laboratories, Bedson Building, Newcastle Upon Tyne, NE1 7RU, UK
| | - D A Allwood
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Maplin Street, Sheffield, S1 3JD, UK
| | - G J Leggett
- Department of Chemistry, University of Sheffield, Dainton Building, Brook Hill, S3 7HF, UK
| | - J J Miles
- School of Computer Science, University of Manchester, Kilburn Building, Oxford Road, Manchester, M13 9PL, UK
| | - S S Staniland
- Department of Chemistry, University of Sheffield, Dainton Building, Brook Hill, S3 7HF, UK
| | - K Critchley
- School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
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Shepley PM, Rushforth AW, Wang M, Burnell G, Moore TA. Modification of perpendicular magnetic anisotropy and domain wall velocity in Pt/Co/Pt by voltage-induced strain. Sci Rep 2015; 5:7921. [PMID: 25605499 PMCID: PMC4300497 DOI: 10.1038/srep07921] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/10/2014] [Indexed: 11/09/2022] Open
Abstract
The perpendicular magnetic anisotropy Keff, magnetization reversal, and field-driven domain wall velocity in the creep regime are modified in Pt/Co(0.85–1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. Keff, measured by the extraordinary Hall effect, is reduced by 10 kJ/m3 by tensile strain out-of-plane εz = 9 × 10−4, independently of the film thickness, indicating a dominant volume contribution to the magnetostriction. The same strain reduces the coercive field by 2–4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers. We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.
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Affiliation(s)
- P M Shepley
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - A W Rushforth
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - M Wang
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - G Burnell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - T A Moore
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
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