The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Ron Jansen - One of the best experts on this subject based on the ideXlab platform.
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Spin heat accumulation induced by Tunneling from a ferromagnet.
Physical review letters, 2014Co-Authors: Ivan J. Vera-marun, Van Bart Wees, Ron JansenAbstract:An electric current from a ferromagnet into a nonmagnetic material can induce a spin-dependent electron temperature. Here, it is shown that this spin heat accumulation, when created by Tunneling from a ferromagnet, produces a non-negligible voltage signal that is comparable to that due to the coexisting electrical spin accumulation and can give a different Hanle spin precession signature. The effect is governed by the spin polarization of the Peltier coefficient of the Tunnel contact, its Seebeck coefficient, and the spin heat resistance of the nonmagnetic material, which is related to the electrical spin resistance by a spin-Wiedemann-Franz law. Moreover, spin heat injection is subject to a heat conductivity mismatch that is overcome if the Tunnel Interface has a sufficiently large resistance.
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Crystal-induced anisotropy of spin accumulation in Si/MgO/Fe and Si/Al2O3/ferromagnet Tunnel devices
Physical Review B, 2013Co-Authors: S. Sharma, Hidekazu Saito, Shinji Yuasa, Van Bart Wees, Aurélie Spiesser, Ron JansenAbstract:The effect of crystalline order on the anisotropy of spin accumulation in Si/oxide/ferromagnet Tunnel devices has been investigated. The spin accumulation induced electrically in the silicon changes when the magnetization of the ferromagnet is rotated either from in-plane to perpendicular to the Tunnel Interface or when it is rotated within the plane of the magnetic layer. A fourfold in-plane anisotropy, which reflects the crystalline nature of the Tunnel contact, is observed not only for crystalline MgO/Fe contacts, but also for devices with amorphous Al2O3 Tunnel barrier and polycrystalline ferromagnetic electrode. The in-plane anisotropy is attributed to the direct coupling of states from the ferromagnet to those in the Si, as in coherent Tunneling, causing anisotropy in devices in which only the nonmagnetic (Si) electrode is crystalline. DOI: 10.1103/PhysRevB.87.085307
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Anisotropy of spin polarization and spin accumulation in Si/Al2O3/ferromagnet Tunnel devices
Physical Review B, 2012Co-Authors: S. Sharma, Saroj P. Dash, Hidekazu Saito, Shinji Yuasa, B. J. Van Wees, Ron JansenAbstract:The contribution of the spin accumulation to Tunneling anisotropy in Si/Al2O3/ferromagnet devices was investigated. Rotation of the magnetization of the ferromagnet from in-plane to perpendicular to the Tunnel Interface reveals a Tunneling anisotropy that depends on the type of the ferromagnet (Fe or Ni) and on the doping of the Si (n or p type). Analysis shows that different contributions to the anisotropy coexist. Besides the regular Tunneling anisotropic magnetoresistance, we identify a contribution due to anisotropy of the Tunnel spin polarization of the oxide/ferromagnet Interface. This causes the spin accumulation to be anisotropic, i.e., dependent on the absolute orientation of the magnetization of the ferromagnet.
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Spin precession and decoherence near an Interface with a ferromagnet
arXiv: Mesoscale and Nanoscale Physics, 2011Co-Authors: Saroj P. Dash, S. Sharma, J. C. Le Breton, H. Jaffrès, J. Peiro, J. M. George, Aristide Lemaître, Ron JansenAbstract:The creation of spin polarization in non-magnetic media via electrical spin injection from a ferromagnetic Tunnel contact was recently achieved for metals, semiconductors, organic and carbon-based materials including graphene. Yet, much of the basic behavior is heavily debated, including the unexpectedly short spin lifetimes observed, and the magnitude and sign of the induced polarization. Here we demonstrate, using semiconductor/Al2O3/ferromagnet Tunnel structures based on silicon or GaAs, that local magnetostatic fields dramatically alter and even dominate spin polarization and spin dynamics near the Tunnel Interface. Spin precession in inhomogeneous magnetic fields arising from Interface roughness is shown to reduce the spin accumulation up to tenfold, and causes it to be inhomogeneous and non-collinear with the injector magnetization. The inverted Hanle effect serves as experimental signature. Additionally, the measured spin lifetime exhibits an apparent reduction, and for silicon at room temperature it is shown that it is significantly larger than previously extracted. Not limited to semiconductors, this phenomenon modifies, but potentially also allows control of spins near magnetic Interfaces in various spintronic structures.
Bernard Pannetier - One of the best experts on this subject based on the ideXlab platform.
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Quasiparticle-diffusion-based heating in superconductor Tunneling microcoolers
Physical Review B, 2009Co-Authors: Sukumar Rajauria, Hervé Courtois, Bernard PannetierAbstract:In a hybrid Superconductor - Insulator - Normal metal Tunnel junction biased just below the gap, the extraction of hot electrons out of the normal metal results in electronic cooling effect. The quasiparticles injected in the superconductor accumulate near the Tunnel Interface, thus increasing the effective superconductor temperature. We propose a simple model for the diffusion of excess quasiparticles in a superconducting strip with an additional trap junction. This diffusion model has a complete analytic solution, which depends on experimentally accessible parameters. We find that the accumulated quasiparticles near the junction reduce the efficiency of the device. This study is also relevant to more general situations making use of superconducting Tunnel junctions, as low temperature detectors.
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Quasiparticle diffusion based heating in superconductor Tunneling micro-coolers
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2009Co-Authors: Bernard Pannetier, Hervé Courtois, Sukumar RajauriaAbstract:In a hybrid Superconductor - Insulator - Normal metal Tunnel junction biased just below the gap, the extraction of hot electrons out of the normal metal results in electronic cooling effect. The quasiparticles injected in the superconductor accumulate near the Tunnel Interface, thus increasing the effective superconductor temperature. We propose a simple model for the diffusion of excess quasiparticles in a superconducting strip with an additional trap junction. This diffusion model has a complete analytic solution, which depends on experimentally accessible parameters. We find that the accumulated quasiparticles near the junction reduce the efficiency of the device. This study is also relevant to more general situations making use of superconducting Tunnel junctions, as low temperature detectors.
Sukumar Rajauria - One of the best experts on this subject based on the ideXlab platform.
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Quasiparticle-diffusion-based heating in superconductor Tunneling microcoolers
Physical Review B, 2009Co-Authors: Sukumar Rajauria, Hervé Courtois, Bernard PannetierAbstract:In a hybrid Superconductor - Insulator - Normal metal Tunnel junction biased just below the gap, the extraction of hot electrons out of the normal metal results in electronic cooling effect. The quasiparticles injected in the superconductor accumulate near the Tunnel Interface, thus increasing the effective superconductor temperature. We propose a simple model for the diffusion of excess quasiparticles in a superconducting strip with an additional trap junction. This diffusion model has a complete analytic solution, which depends on experimentally accessible parameters. We find that the accumulated quasiparticles near the junction reduce the efficiency of the device. This study is also relevant to more general situations making use of superconducting Tunnel junctions, as low temperature detectors.
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Quasiparticle diffusion based heating in superconductor Tunneling micro-coolers
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2009Co-Authors: Bernard Pannetier, Hervé Courtois, Sukumar RajauriaAbstract:In a hybrid Superconductor - Insulator - Normal metal Tunnel junction biased just below the gap, the extraction of hot electrons out of the normal metal results in electronic cooling effect. The quasiparticles injected in the superconductor accumulate near the Tunnel Interface, thus increasing the effective superconductor temperature. We propose a simple model for the diffusion of excess quasiparticles in a superconducting strip with an additional trap junction. This diffusion model has a complete analytic solution, which depends on experimentally accessible parameters. We find that the accumulated quasiparticles near the junction reduce the efficiency of the device. This study is also relevant to more general situations making use of superconducting Tunnel junctions, as low temperature detectors.
Frank W. J. Hekking - One of the best experts on this subject based on the ideXlab platform.
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Subgap noise of a superconductor-normal-metal Tunnel Interface
Physical Review B - Condensed Matter and Materials Physics, 2004Co-Authors: Fabio Pistolesi, Frank W. J. HekkingAbstract:It is well established that the subgap conductivity through a normal-metal-insulator-superconductor (NIS) Tunnel junction is strongly affected by interference of electron waves scattered by impurities. In this paper we investigate how the same phenomenon affects the low frequency current noise, S, for voltages V and temperatures T much smaller than the superconducting gap. If the normal metal is at equilibrium we find that the simple relation S(V,T) = 4e rm coth (eV/T) I(V,T) holds quite generally even for non-linear I-V characteristics. Only when the normal metal is out of equilibrium, noise and current become independent. Their ratio, the Fano factor, depends then on the details of the layout.
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Subgap conductivity of a superconductor-normal-metal Tunnel Interface.
Physical review. B Condensed matter, 1994Co-Authors: Frank W. J. Hekking, Yu. V. NazarovAbstract:At low temperatures, the transport through a superconductor--normal-metal Tunnel Interface is due to Tunneling of electrons in pairs. We show that the rate for this process is often determined by the interference of the electron waves on a space scale determined by the coherence length. Therefore, the subgap current strongly depends on the layout of the electrodes within this space scale. The approach developed allows us to evaluate the subgap current for different layouts of interest.
S. Sharma - One of the best experts on this subject based on the ideXlab platform.
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Crystal-induced anisotropy of spin accumulation in Si/MgO/Fe and Si/Al2O3/ferromagnet Tunnel devices
Physical Review B, 2013Co-Authors: S. Sharma, Hidekazu Saito, Shinji Yuasa, Van Bart Wees, Aurélie Spiesser, Ron JansenAbstract:The effect of crystalline order on the anisotropy of spin accumulation in Si/oxide/ferromagnet Tunnel devices has been investigated. The spin accumulation induced electrically in the silicon changes when the magnetization of the ferromagnet is rotated either from in-plane to perpendicular to the Tunnel Interface or when it is rotated within the plane of the magnetic layer. A fourfold in-plane anisotropy, which reflects the crystalline nature of the Tunnel contact, is observed not only for crystalline MgO/Fe contacts, but also for devices with amorphous Al2O3 Tunnel barrier and polycrystalline ferromagnetic electrode. The in-plane anisotropy is attributed to the direct coupling of states from the ferromagnet to those in the Si, as in coherent Tunneling, causing anisotropy in devices in which only the nonmagnetic (Si) electrode is crystalline. DOI: 10.1103/PhysRevB.87.085307
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Anisotropy of spin polarization and spin accumulation in Si/Al2O3/ferromagnet Tunnel devices
Physical Review B, 2012Co-Authors: S. Sharma, Saroj P. Dash, Hidekazu Saito, Shinji Yuasa, B. J. Van Wees, Ron JansenAbstract:The contribution of the spin accumulation to Tunneling anisotropy in Si/Al2O3/ferromagnet devices was investigated. Rotation of the magnetization of the ferromagnet from in-plane to perpendicular to the Tunnel Interface reveals a Tunneling anisotropy that depends on the type of the ferromagnet (Fe or Ni) and on the doping of the Si (n or p type). Analysis shows that different contributions to the anisotropy coexist. Besides the regular Tunneling anisotropic magnetoresistance, we identify a contribution due to anisotropy of the Tunnel spin polarization of the oxide/ferromagnet Interface. This causes the spin accumulation to be anisotropic, i.e., dependent on the absolute orientation of the magnetization of the ferromagnet.
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Spin precession and decoherence near an Interface with a ferromagnet
arXiv: Mesoscale and Nanoscale Physics, 2011Co-Authors: Saroj P. Dash, S. Sharma, J. C. Le Breton, H. Jaffrès, J. Peiro, J. M. George, Aristide Lemaître, Ron JansenAbstract:The creation of spin polarization in non-magnetic media via electrical spin injection from a ferromagnetic Tunnel contact was recently achieved for metals, semiconductors, organic and carbon-based materials including graphene. Yet, much of the basic behavior is heavily debated, including the unexpectedly short spin lifetimes observed, and the magnitude and sign of the induced polarization. Here we demonstrate, using semiconductor/Al2O3/ferromagnet Tunnel structures based on silicon or GaAs, that local magnetostatic fields dramatically alter and even dominate spin polarization and spin dynamics near the Tunnel Interface. Spin precession in inhomogeneous magnetic fields arising from Interface roughness is shown to reduce the spin accumulation up to tenfold, and causes it to be inhomogeneous and non-collinear with the injector magnetization. The inverted Hanle effect serves as experimental signature. Additionally, the measured spin lifetime exhibits an apparent reduction, and for silicon at room temperature it is shown that it is significantly larger than previously extracted. Not limited to semiconductors, this phenomenon modifies, but potentially also allows control of spins near magnetic Interfaces in various spintronic structures.
