The Experts below are selected from a list of 15345 Experts worldwide ranked by ideXlab platform
J B Dunlop - One of the best experts on this subject based on the ideXlab platform.
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the fluctuation field and anomalous magnetic viscosity in commercial ndfeb alloys alnico and the bulk amorphous ferromagnets nd60fe30al10nd60fe30al10 and nd60fe20co10al10nd60fe20co10al10
Journal of Magnetism and Magnetic Materials, 2008Co-Authors: S J Collocott, J B DunlopAbstract:The fluctuation field, HfHf, is a useful parameter for characterising any ferromagnetic material that displays hysteresis, as it is a measure of the thermally activated rate processes that govern Magnetisation reversals. Anomalous magnetic viscosity, i.e. nonmonotonic behaviour of the time dependent Magnetisation, where the Magnetisation is seen to increase, reach a peak, and then decrease, has been observed on both the upper and lower branches of minor loops or recoil curves in some ferromagnetic materials. Parameters relevant to the Preisach model are discussed as to their usefulness in predicting anomalous magnetic viscosity in ferromagnetic materials. This is done with reference to measurements of HfHf and the time dependent Magnetisation in commercial NdFeB alloys, AlNiCo and the bulk amorphous ferromagnets Nd60Fe30Al10Nd60Fe30Al10 and Nd60Fe20Co10Al10Nd60Fe20Co10Al10.
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the fluctuation field and anomalous magnetic viscosity in commercial ndfeb alloys alnico and the bulk amorphous ferromagnets nd60fe30al10 and nd60fe20co10al10
Journal of Magnetism and Magnetic Materials, 2008Co-Authors: S J Collocott, J B DunlopAbstract:Abstract The fluctuation field, H f , is a useful parameter for characterising any ferromagnetic material that displays hysteresis, as it is a measure of the thermally activated rate processes that govern Magnetisation reversals. Anomalous magnetic viscosity, i.e. nonmonotonic behaviour of the time dependent Magnetisation, where the Magnetisation is seen to increase, reach a peak, and then decrease, has been observed on both the upper and lower branches of minor loops or recoil curves in some ferromagnetic materials. Parameters relevant to the Preisach model are discussed as to their usefulness in predicting anomalous magnetic viscosity in ferromagnetic materials. This is done with reference to measurements of H f and the time dependent Magnetisation in commercial NdFeB alloys, AlNiCo and the bulk amorphous ferromagnets Nd 60 Fe 30 Al 10 and Nd 60 Fe 20 Co 10 Al 10 .
S J Collocott - One of the best experts on this subject based on the ideXlab platform.
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the fluctuation field and anomalous magnetic viscosity in commercial ndfeb alloys alnico and the bulk amorphous ferromagnets nd60fe30al10nd60fe30al10 and nd60fe20co10al10nd60fe20co10al10
Journal of Magnetism and Magnetic Materials, 2008Co-Authors: S J Collocott, J B DunlopAbstract:The fluctuation field, HfHf, is a useful parameter for characterising any ferromagnetic material that displays hysteresis, as it is a measure of the thermally activated rate processes that govern Magnetisation reversals. Anomalous magnetic viscosity, i.e. nonmonotonic behaviour of the time dependent Magnetisation, where the Magnetisation is seen to increase, reach a peak, and then decrease, has been observed on both the upper and lower branches of minor loops or recoil curves in some ferromagnetic materials. Parameters relevant to the Preisach model are discussed as to their usefulness in predicting anomalous magnetic viscosity in ferromagnetic materials. This is done with reference to measurements of HfHf and the time dependent Magnetisation in commercial NdFeB alloys, AlNiCo and the bulk amorphous ferromagnets Nd60Fe30Al10Nd60Fe30Al10 and Nd60Fe20Co10Al10Nd60Fe20Co10Al10.
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the fluctuation field and anomalous magnetic viscosity in commercial ndfeb alloys alnico and the bulk amorphous ferromagnets nd60fe30al10 and nd60fe20co10al10
Journal of Magnetism and Magnetic Materials, 2008Co-Authors: S J Collocott, J B DunlopAbstract:Abstract The fluctuation field, H f , is a useful parameter for characterising any ferromagnetic material that displays hysteresis, as it is a measure of the thermally activated rate processes that govern Magnetisation reversals. Anomalous magnetic viscosity, i.e. nonmonotonic behaviour of the time dependent Magnetisation, where the Magnetisation is seen to increase, reach a peak, and then decrease, has been observed on both the upper and lower branches of minor loops or recoil curves in some ferromagnetic materials. Parameters relevant to the Preisach model are discussed as to their usefulness in predicting anomalous magnetic viscosity in ferromagnetic materials. This is done with reference to measurements of H f and the time dependent Magnetisation in commercial NdFeB alloys, AlNiCo and the bulk amorphous ferromagnets Nd 60 Fe 30 Al 10 and Nd 60 Fe 20 Co 10 Al 10 .
S Collin - One of the best experts on this subject based on the ideXlab platform.
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a transmission electron microscope study of neel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction
Scientific Reports, 2018Co-Authors: S Mcvitie, Sean Hughes, K Fallon, S Mcfadzean, D Mcgrouther, M Krajnak, William Legrand, Davide Maccariello, S CollinAbstract:Skyrmions in ultrathin ferromagnetic metal (FM)/heavy metal (HM) multilayer systems produced by conventional sputtering methods have recently generated huge interest due to their applications in the field of spintronics. The sandwich structure with two correctly-chosen heavy metal layers provides an additive interfacial exchange interaction which promotes domain wall or skyrmion spin textures that are Neel in character and with a fixed chirality. Lorentz transmission electron microscopy (TEM) is a high resolution method ideally suited to quantitatively image such chiral magnetic configurations. When allied with physical and chemical TEM analysis of both planar and cross-sectional samples, key length scales such as grain size and the chiral variation of the Magnetisation variation have been identified and measured. We present data showing the importance of the grain size (mostly < 10 nm) measured from direct imaging and its potential role in describing observed behaviour of isolated skyrmions (diameter < 100 nm). In the latter the region in which the magnetization rotates is measured to be around 30 nm. Such quantitative information on the multiscale Magnetisation variations in the system is key to understanding and exploiting the behaviour of skyrmions for future applications in information storage and logic devices.
M Krajnak - One of the best experts on this subject based on the ideXlab platform.
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a transmission electron microscope study of neel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction
Scientific Reports, 2018Co-Authors: S Mcvitie, Sean Hughes, K Fallon, S Mcfadzean, D Mcgrouther, M Krajnak, William Legrand, Davide Maccariello, S CollinAbstract:Skyrmions in ultrathin ferromagnetic metal (FM)/heavy metal (HM) multilayer systems produced by conventional sputtering methods have recently generated huge interest due to their applications in the field of spintronics. The sandwich structure with two correctly-chosen heavy metal layers provides an additive interfacial exchange interaction which promotes domain wall or skyrmion spin textures that are Neel in character and with a fixed chirality. Lorentz transmission electron microscopy (TEM) is a high resolution method ideally suited to quantitatively image such chiral magnetic configurations. When allied with physical and chemical TEM analysis of both planar and cross-sectional samples, key length scales such as grain size and the chiral variation of the Magnetisation variation have been identified and measured. We present data showing the importance of the grain size (mostly < 10 nm) measured from direct imaging and its potential role in describing observed behaviour of isolated skyrmions (diameter < 100 nm). In the latter the region in which the magnetization rotates is measured to be around 30 nm. Such quantitative information on the multiscale Magnetisation variations in the system is key to understanding and exploiting the behaviour of skyrmions for future applications in information storage and logic devices.
Fujishiro H - One of the best experts on this subject based on the ideXlab platform.
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Pulsed-field Magnetisation of Y-Ba-Cu-O bulk superconductors fabricated by the infiltration growth technique
'Organisation for Economic Co-Operation and Development (OECD)', 2020Co-Authors: Namburi, Devendra K, Fujishiro H, Takahashi K, Hirano T, Kamada T, Shi Y-h, Cardwell D A, Durrell J H, Ainslie M DAbstract:Funder: King Abdulaziz City for Science and Technology; doi: http://dx.doi.org/10.13039/501100004919Abstract: Bulk high temperature superconductors based on the rare-earth copper oxides can be used effectively as trapped field magnets capable of generating large magnetic fields. The top-seeded infiltration growth (TSIG) processing technique can provide a more homogeneous microstructure and therefore more uniform superconducting properties than samples grown using conventional melt growth processes. In the present investigation, the properties of bulk, single grain superconductors processed by TSIG and magnetised by the pulsed-field Magnetisation technique using a copper-wound solenoid have been studied. A trapped field of ∼3 T has been achieved in a 2-step buffer-assisted TSIG-processed Y-Ba-Cu-O (YBCO) sample at 40 K by magnetising the bulk superconductor completely via a single-pulse Magnetisation process. Samples were also subjected to pulsed-field Magnetisation at 65 K and by conventional field-cooled Magnetisation at 77 K for comparison. Good correlation was observed between the microstructures, critical current densities and trapped field performance of bulk samples fabricated by TSIG and magnetised by pulsed-field and field-cooled Magnetisation. The homogeneous distribution of Y2BaCuO5 inclusions within the microstructure of bulk YBCO samples fabricated by the 2-step buffer-assisted TSIG process reduces inhomogeneous flux penetration into the interior of the sample. This, in turn, results in a lower temperature rise of the bulk superconductor during the pulsed-field Magnetisation process and a more effective and reliable Magnetisation process
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Pulsed-field Magnetisation of Y-Ba-Cu-O bulk superconductors fabricated by the infiltration growth technique
'Organisation for Economic Co-Operation and Development (OECD)', 2020Co-Authors: Namburi Devendra, Fujishiro H, Takahashi K, Cardwell David, Durrell John, Hirano T, Kamada T, Shi Yunhua, Ainslie MarkAbstract:Bulk high temperature superconductors based on the rare-earth copper oxides can be used effectively as trapped field magnets capable of generating large magnetic fields. The top-seeded infiltration growth (TSIG) processing technique can provide a more homogeneous microstructure and therefore more uniform superconducting properties than samples grown using conventional melt growth processes. In the present investigation, the properties of bulk, single grain superconductors processed by TSIG and magnetised by the pulsed-field Magnetisation technique using a copper-wound solenoid have been studied. A trapped field of ~ 3 T has been achieved in a 2-step buffer-assisted TSIG-processed Y-Ba-Cu-O (YBCO) sample at 40 K by magnetising the bulk superconductor completely via a single-pulse Magnetisation process. Samples were also subjected to pulsed-field Magnetisation at 65 K and by conventional field-cooled Magnetisation at 77 K for comparison. Good correlation was observed between the microstructures, critical current densities and trapped field performance of bulk samples fabricated by TSIG and magnetised by pulsed-field and field-cooled Magnetisation. The homogeneous distribution of Y2BaCuO5 inclusions within the microstructure of bulk YBCO samples fabricated by the 2-step buffer-assisted TSIG process reduces inhomogeneous flux penetration into the interior of the sample. This, in turn, results in a lower temperature rise of the bulk superconductor during the pulsed-field Magnetisation process and a more effective and reliable Magnetisation process.KACS
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Pulsed-field Magnetisation of Y-Ba-Cu-O bulk superconductors fabricated by the infiltration growth technique
2020Co-Authors: Dk Namburi, Fujishiro H, Takahashi K, Hirano T, Kamada T, Yh Shi, Da Cardwell, J H DurrellAbstract:© 2020 The Author(s). Bulk high temperature superconductors based on the rare-earth copper oxides can be used effectively as trapped field magnets capable of generating large magnetic fields. The top-seeded infiltration growth (TSIG) processing technique can provide a more homogeneous microstructure and therefore more uniform superconducting properties than samples grown using conventional melt growth processes. In the present investigation, the properties of bulk, single grain superconductors processed by TSIG and magnetised by the pulsed-field Magnetisation technique using a copper-wound solenoid have been studied. A trapped field of ∼3 T has been achieved in a 2-step buffer-assisted TSIG-processed Y-Ba-Cu-O (YBCO) sample at 40 K by magnetising the bulk superconductor completely via a single-pulse Magnetisation process. Samples were also subjected to pulsed-field Magnetisation at 65 K and by conventional field-cooled Magnetisation at 77 K for comparison. Good correlation was observed between the microstructures, critical current densities and trapped field performance of bulk samples fabricated by TSIG and magnetised by pulsed-field and field-cooled Magnetisation. The homogeneous distribution of Y2BaCuO5 inclusions within the microstructure of bulk YBCO samples fabricated by the 2-step buffer-assisted TSIG process reduces inhomogeneous flux penetration into the interior of the sample. This, in turn, results in a lower temperature rise of the bulk superconductor during the pulsed-field Magnetisation process and a more effective and reliable Magnetisation process
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Numerical modelling of mechanical stresses in bulk superconductor magnets with and without mechanical reinforcement
'Organisation for Economic Co-Operation and Development (OECD)', 2019Co-Authors: Ainslie Mark, Huang Danny, Fujishiro H, Chaddock J, Takahashi K, Namba S, Cardwell David, Durrell JohnAbstract:The magnetic field trapping capability of a bulk superconductor is essentially determined by the critical current density, Jc(B, T), of the material. With state-of-the-art bulk (RE)BCO (where RE = rare earth or Y) materials it is clear that trapped fields of over 20 T are potentially achievable. However, the large Lorentz forces, FL = J × B, that develop during Magnetisation of the sample lead to large mechanical stresses that can result in mechanical failure. The radial forces are tensile and the resulting stresses are not resisted well because of the brittle ceramic nature of (RE)BCO materials. Where fields of more than 17 T have been achieved, the samples were reinforced mechanically using resin impregnation and carbon-fibre wrapping or shrink-fit stainless steel. In this paper, two-dimensional (2D) axisymmetric and three-dimensional (3D) finite-element models based on the H-formulation, implemented in the commercial finite element software package COMSOL Multiphysics, are used to provide a comprehensive picture of the mechanical stresses in bulk superconductor magnets with and without mechanical reinforcement during field-cooled magnetization (FCM). The chosen modelling framework couples together electromagnetic, thermal and structural mechanics models, and is extremely flexible in allowing the inclusion of various Magnetisation processes and conditions, as well as detailed and realistic properties of the materials involved. The 2D model – a faster route to parametric optimisation – is firstly used to investigate the influence of the ramp rate of the applied field and any heat generated in the bulk. Finally, the 3D model is used to investigate the influence of inhomogeneous Jc(B, T) properties around the ab-plane of the bulk superconductor on the developed mechanical stress.EPSRC Early Career Fellowship EP/P020313/1 JSPS KAKENHI Grant No. JP15K0464
