The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Sadamichi Maekawa - One of the best experts on this subject based on the ideXlab platform.
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spinmotive force with static and uniform magnetization induced by a time varying electric field
Physical Review B, 2013Co-Authors: Yuta Yamane, Junichi Ieda, Sadamichi MaekawaAbstract:CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan(Dated: August 13, 2013)A new spinmotive force is predicted in Ferromagnets with spin-orbit coupling. By extending thetheory of spinmotive force, we show that a time-varying electric field can induce a spinmotive forcewith static and uniform magnetization. This spinmotive has two advantages; it can be detected freefrom the inductive voltage owing to the absence of dynamical magnetization and it can be tuned byelectric fields. To observe the effect, we propose two experimental setups: electric voltage measure-ment in a single Ferromagnet and spin injection from a Ferromagnet into an attached nonmagneticconductor.I. INTRODUCTION
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Spin Waves, Spin Currents and Spin Seebeck Effect
Topics in Applied Physics, 2012Co-Authors: Hiroto Adachi, Sadamichi MaekawaAbstract:The spin Seebeck effect is now established as a universal aspect of Ferromagnets that enables thermal injection of spin currents from a Ferromagnet into attached nonmagnetic metals over macroscopic scale of several millimeters. We show that the spin-wave degrees of freedom play a crucial role in the spin Seebeck effect.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions
Journal of Magnetism and Magnetic Materials, 2004Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract A theory of Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions is presented. In the superconductor, the spin polarized quasiparticle current converts to the spinless supercurrent in the range of penetration depth from the interfaces. Therefore, when the thickness of the superconductor is comparable to or smaller than the penetration depth, the current strongly depends on the relative orientation of magnetization of the Ferromagnets. We show the effect of spin injection via Andreev reflection on the current flowing through the present system.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures
Physica E-low-dimensional Systems & Nanostructures, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract We study theoretically the effect of Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures. The spin-polarized quasiparticle current penetrates to the superconductor in the range of penetration depth from the interfaces, and thus the current depends on the relative orientation of magnetization of the Ferromagnets. We show that the current is controlled by the Andreev reflection at the interfaces.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet double junction systems
Physical Review B, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:We present a theory of Andreev reflection in a Ferromagnet/superconductor/Ferromagnet double junction system. In the Andreev reflection process, the injected spin polarized quasiparticles convert into Cooper pairs in the superconductor within the range of the penetration depth from the interface. When the thickness of the superconductor is smaller than or comparable to the penetration depth, the spin polarized quasiparticles pass through the superconductor and therefore the electric current depends on the relative orientation of magnetizations of the Ferromagnets. The dependences of the magnetoresistance on the thickness of the superconductor, temperature, the exchange field of the Ferromagnets, and the height of the interfacial barriers are analyzed. Our theory explains recent experimental results well.
Hiroshi Imamura - One of the best experts on this subject based on the ideXlab platform.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions
Journal of Magnetism and Magnetic Materials, 2004Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract A theory of Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions is presented. In the superconductor, the spin polarized quasiparticle current converts to the spinless supercurrent in the range of penetration depth from the interfaces. Therefore, when the thickness of the superconductor is comparable to or smaller than the penetration depth, the current strongly depends on the relative orientation of magnetization of the Ferromagnets. We show the effect of spin injection via Andreev reflection on the current flowing through the present system.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures
Physica E-low-dimensional Systems & Nanostructures, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract We study theoretically the effect of Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures. The spin-polarized quasiparticle current penetrates to the superconductor in the range of penetration depth from the interfaces, and thus the current depends on the relative orientation of magnetization of the Ferromagnets. We show that the current is controlled by the Andreev reflection at the interfaces.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet double junction systems
Physical Review B, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:We present a theory of Andreev reflection in a Ferromagnet/superconductor/Ferromagnet double junction system. In the Andreev reflection process, the injected spin polarized quasiparticles convert into Cooper pairs in the superconductor within the range of the penetration depth from the interface. When the thickness of the superconductor is smaller than or comparable to the penetration depth, the spin polarized quasiparticles pass through the superconductor and therefore the electric current depends on the relative orientation of magnetizations of the Ferromagnets. The dependences of the magnetoresistance on the thickness of the superconductor, temperature, the exchange field of the Ferromagnets, and the height of the interfacial barriers are analyzed. Our theory explains recent experimental results well.
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Spin injection and magnetoresistance in Ferromagnet– superconductor–Ferromagnet tunnel junctions
Journal of Applied Physics, 2000Co-Authors: Saburo Takahashi, Hiroshi Imamura, Sadamichi MaekawaAbstract:We theoretically study the spin-dependent transport in a Ferromagnet–superconductor–Ferromagnet double barrier tunnel junction. The spin-polarized tunneling currents give rise to spin imbalance in the superconductor. The resulting nonequilibrium spin density suppresses the superconductivity with increase of the tunneling currents. We focus on the effect of asymmetry in the double tunnel junction, where the barrier height of the tunnel junction and the spin polarization of the Ferromagnets are different, on spin injection, and discuss how the superconductivity is suppressed in the asymmetric junction. Our results explain recent experimental results on the critical current suppression in high-Tc superconductors by spin injection.
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spin imbalance and magnetoresistance in Ferromagnet superconductor Ferromagnet double tunnel junctions
Physical Review Letters, 1999Co-Authors: S Takahashi, Hiroshi Imamura, Sadamichi MaekawaAbstract:We theoretically study the spin-dependent transport in a Ferromagnet/superconductor/Ferromagnet double tunnel junction. The tunneling current in the antiFerromagnetic alignment of the magnetizations gives rise to a spin imbalance in the superconductor. The resulting nonequilibrium spin density strongly suppresses the superconductivity with increase of bias voltage and destroys it at a critical voltage ${V}_{c}$. The results provide a new method not only for measuring the spin polarization of Ferromagnets but also for controlling superconductivity and tunnel magnetoresistance by applying a bias voltage.
Saburo Takahashi - One of the best experts on this subject based on the ideXlab platform.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions
Journal of Magnetism and Magnetic Materials, 2004Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract A theory of Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions is presented. In the superconductor, the spin polarized quasiparticle current converts to the spinless supercurrent in the range of penetration depth from the interfaces. Therefore, when the thickness of the superconductor is comparable to or smaller than the penetration depth, the current strongly depends on the relative orientation of magnetization of the Ferromagnets. We show the effect of spin injection via Andreev reflection on the current flowing through the present system.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures
Physica E-low-dimensional Systems & Nanostructures, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract We study theoretically the effect of Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures. The spin-polarized quasiparticle current penetrates to the superconductor in the range of penetration depth from the interfaces, and thus the current depends on the relative orientation of magnetization of the Ferromagnets. We show that the current is controlled by the Andreev reflection at the interfaces.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet double junction systems
Physical Review B, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:We present a theory of Andreev reflection in a Ferromagnet/superconductor/Ferromagnet double junction system. In the Andreev reflection process, the injected spin polarized quasiparticles convert into Cooper pairs in the superconductor within the range of the penetration depth from the interface. When the thickness of the superconductor is smaller than or comparable to the penetration depth, the spin polarized quasiparticles pass through the superconductor and therefore the electric current depends on the relative orientation of magnetizations of the Ferromagnets. The dependences of the magnetoresistance on the thickness of the superconductor, temperature, the exchange field of the Ferromagnets, and the height of the interfacial barriers are analyzed. Our theory explains recent experimental results well.
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Spin injection and magnetoresistance in Ferromagnet– superconductor–Ferromagnet tunnel junctions
Journal of Applied Physics, 2000Co-Authors: Saburo Takahashi, Hiroshi Imamura, Sadamichi MaekawaAbstract:We theoretically study the spin-dependent transport in a Ferromagnet–superconductor–Ferromagnet double barrier tunnel junction. The spin-polarized tunneling currents give rise to spin imbalance in the superconductor. The resulting nonequilibrium spin density suppresses the superconductivity with increase of the tunneling currents. We focus on the effect of asymmetry in the double tunnel junction, where the barrier height of the tunnel junction and the spin polarization of the Ferromagnets are different, on spin injection, and discuss how the superconductivity is suppressed in the asymmetric junction. Our results explain recent experimental results on the critical current suppression in high-Tc superconductors by spin injection.
Taro Yamashita - One of the best experts on this subject based on the ideXlab platform.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions
Journal of Magnetism and Magnetic Materials, 2004Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract A theory of Andreev reflection in Ferromagnet/superconductor/Ferromagnet junctions is presented. In the superconductor, the spin polarized quasiparticle current converts to the spinless supercurrent in the range of penetration depth from the interfaces. Therefore, when the thickness of the superconductor is comparable to or smaller than the penetration depth, the current strongly depends on the relative orientation of magnetization of the Ferromagnets. We show the effect of spin injection via Andreev reflection on the current flowing through the present system.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures
Physica E-low-dimensional Systems & Nanostructures, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:Abstract We study theoretically the effect of Andreev reflection in Ferromagnet/superconductor/Ferromagnet structures. The spin-polarized quasiparticle current penetrates to the superconductor in the range of penetration depth from the interfaces, and thus the current depends on the relative orientation of magnetization of the Ferromagnets. We show that the current is controlled by the Andreev reflection at the interfaces.
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Andreev reflection in Ferromagnet/superconductor/Ferromagnet double junction systems
Physical Review B, 2003Co-Authors: Taro Yamashita, Hiroshi Imamura, Saburo Takahashi, Sadamichi MaekawaAbstract:We present a theory of Andreev reflection in a Ferromagnet/superconductor/Ferromagnet double junction system. In the Andreev reflection process, the injected spin polarized quasiparticles convert into Cooper pairs in the superconductor within the range of the penetration depth from the interface. When the thickness of the superconductor is smaller than or comparable to the penetration depth, the spin polarized quasiparticles pass through the superconductor and therefore the electric current depends on the relative orientation of magnetizations of the Ferromagnets. The dependences of the magnetoresistance on the thickness of the superconductor, temperature, the exchange field of the Ferromagnets, and the height of the interfacial barriers are analyzed. Our theory explains recent experimental results well.
Qing-rong Zheng - One of the best experts on this subject based on the ideXlab platform.
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Oscillations of tunnel magnetoresistance induced by spin-wave excitations in Ferromagnet-Ferromagnet-Ferromagnet double-barrier tunnel junctions
Physical Review B, 2007Co-Authors: Xi Chen, Qing-rong Zheng, Gang SuAbstract:The possibility of quantum oscillations of the tunnel conductance and magnetoresistance induced by spin-wave excitations in a Ferromagnet-Ferromagnet-Ferromagnet double barrier tunnel junction, when the magnetizations of the two side Ferromagnets are aligned antiparallel to that of the middle Ferromagnet, is investigated in a self-consistent manner by means of Keldysh nonequilibrium Green function method. It has been found that owing to the s-d exchange interactions between conduction electrons and the spin density induced by spin accumulation in the middle Ferromagnet, the differential conductance and the TMR indeed oscillate with the increase of bias voltage, being consistent with the phenomenon that is observed recently in experiments. The effects of magnon modes, the energy levels of electrons as well as the molecular field in the central Ferromagnet on the oscillatory transport property of the system are also discussed.
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Oscillations of tunnel magnetoresistance induced by spin-wave excitations in Ferromagnet-Ferromagnet-Ferromagnet double-barrier tunnel junctions
Physical Review B, 2007Co-Authors: Xi Chen, Qing-rong ZhengAbstract:The possibility of oscillations of the tunnel conductance and magnetoresistance induced by spin wave excitations in a Ferromagnet-Ferromagnet-Ferromagnet double-barrier tunnel junction, when the magnetizations of the two side Ferromagnets are aligned antiparallel to that of the middle Ferromagnet, is investigated in a self-consistent manner by means of Keldysh nonequilibrium Green's function method. It has been found that owing to the $s\text{\ensuremath{-}}d$ exchange interactions between conduction electrons and the spin density induced by spin accumulation in the middle Ferromagnet, the differential conductance and the tunnel magnetoresistance indeed oscillate with the increase of bias voltage, being qualitatively consistent with the phenomenon that is observed recently in experiments. The effects of magnon modes, the energy levels of electrons, as well as the molecular field in the central Ferromagnet on the oscillatory transport property of the system are also discussed.