Showing papers by "Yaroslav Tserkovnyak published in 2003"
TL;DR: A long-range dynamic interaction between ferromagnetic films separated by normal-metal spacers is reported, which is communicated by nonequilibrium spin currents.
Abstract: A long-range dynamic interaction between ferromagnetic films separated by normal-metal spacers is reported, which is communicated by nonequilibrium spin currents. It is measured by ferromagnetic resonance and explained by an adiabatic spin-pump theory. In such a resonance the spin-pump mechanism of spatially separated magnetic moments leads to an appreciable increase in the resonant linewidth when the resonance fields are well apart, and results in a dramatic linewidth narrowing when the resonant fields approach each other.
340 citations
TL;DR: In this article, it was shown that the spin-current induced magnetization torque can be measured by the angular magnetoresistance of these spin valves, and generalized to arbitrary magnetoelectronic circuits.
Abstract: The electrical resistance of ferromagnetic/normal-metal $(F/N)$ heterostructures depends on the nature of the junctions that may be tunnel barriers, point contacts, or intermetallic interfaces. For all junction types, the resistance of disordered $F/N/F$ perpendicular spin valves as a function of the angle between magnetization vectors is shown to obey a simple universal law. The spin-current induced magnetization torque can be measured by the angular magnetoresistance of these spin valves. The results are generalized to arbitrary magnetoelectronic circuits.
76 citations
TL;DR: In this paper, the role of nonequilibrium spin-current exchange between the ferromagnets in the magnetization precession and switching was investigated, and it was shown that in the absence of an applied bias, the effect of spin transfer can be expressed as magnetic-configuration-dependent Gilbert damping.
Abstract: The dynamics of the magnetic order parameters of ferromagnet/paramagnet/ferromagnet spin valves and isolated ferromagnets may be very different. We investigate the role of the nonequilibrium spin-current exchange between the ferromagnets in the magnetization precession and switching. We find a (low-temperature) critical current bias for a uniform current-induced magnetization excitation in spin valves, which unifies and generalizes previous ideas of Slonczewski and Berger. In the absence of an applied bias, the effect of the spin transfer can be expressed as magnetic-configuration-dependent Gilbert damping.
73 citations
TL;DR: In this article, the Luttinger liquid (LL) nature of elementary excitations in a system consisting of two quantum wires connected by a long narrow tunnel junction at the edge of a GaAs/AlGaAs bilayer heterostructure was revealed.
Abstract: We present theoretical calculations and experimental measurements which reveal the Luttinger-liquid (LL) nature of elementary excitations in a system consisting of two quantum wires connected by a long narrow tunnel junction at the edge of a GaAs/AlGaAs bilayer heterostructure. The boundaries of the wires are important and lead to a characteristic interference pattern in measurements on short junctions. We show that the experimentally observed modulation of the conductance oscillation amplitude as a function of the voltage bias can be accounted for by spin-charge separation of the elementary excitations in the interacting wires. Furthermore, boundaries affect the LL exponents of the voltage and temperature dependence of the tunneling conductance at low energies. We show that the measured temperature dependence of the conductance zero-bias dip as well as the voltage modulation of the conductance oscillation pattern can be used to extract the electron interaction parameters in the wires.
55 citations
TL;DR: The non-Abelian statistics of MR quasiholes is demonstrated explicitly for the first time, confirming the results predicted by conformal field theories.
Abstract: We develop a general framework to (numerically) study adiabatic braiding of quasiholes in fractional quantum Hall systems. Specifically, we investigate the Moore-Read (MR) state at $\ensuremath{
u}=1/2$ filling factor, a known candidate for non-Abelian statistics, which appears to actually occur in nature. The non-Abelian statistics of MR quasiholes is demonstrated explicitly for the first time, confirming the results predicted by conformal field theories.
53 citations
TL;DR: It is shown that the frequency-dependent bulk modulus K(omega) for wavelengths longer than the characteristic structural dimensions of the fluid patches has a similar analytic behavior to the case of a vanishing membrane stiffness and depends on the same parameters of the fluids-distribution topology.
Abstract: A linearized theory of the acoustics of porous elastic formations, such as rocks, saturated with two different viscous fluids is generalized to take into account a pressure discontinuity across the fluid boundaries. The latter can arise due to the surface tension of the membrane separating the fluids. We show that the frequency-dependent bulk modulus K(ω) for wavelengths longer than the characteristic structural dimensions of the fluid patches has a similar analytic behavior to the case of a vanishing membrane stiffness and depends on the same parameters of the fluid-distribution topology. The effect of the capillary stiffness can be accounted for by renormalizing the coefficients of the leading terms in the low-frequency limit of K(ω).
50 citations
TL;DR: In this paper, a magnetoelectronic thin-film transistor is proposed that can display negative differential resistance and gain, where the working principle is the modulation of the soure drain current in a spin valve by the magnetization of a third electrode, which is rotated by the spintorque created by a control spin valve.
Abstract: A magnetoelectronic thin-film transistor is proposed that can display negative differential resistance and gain. The working principle is the modulation of the soure–drain current in a spin valve by the magnetization of a third electrode, which is rotated by the spin-torque created by a control spin valve. The device can operate at room temperature, but in order to be useful, ferromagnetic materials with polarizations close to unity are required.
45 citations
TL;DR: In this article, a magnetoelectronic thin-film transistor is proposed that can display negative differential resistance and gain, where the working principle is the modulation of the soure drain current in a spin valve by the magnetization of a third electrode, which is rotated by the spin-torque created by a control spin-valve.
Abstract: A magnetoelectronic thin-film transistor is proposed that can display negative differential resistance and gain. The working principle is the modulation of the soure-drain current in a spin valve by the magnetization of a third electrode, which is rotated by the spin-torque created by a control spin-valve. The device can operate at room temperature, but in order to be useful, ferromagnetic materials with polarizations close to unity are required.
38 citations
TL;DR: In this article, the authors theoretically study dynamic properties of thin ferromagnetic films in contact with normal metals, and they show that spin flips outside the moving magnetization enhances the overall damping of the magnetization dynamics in accordance with the Gilbert phenomenology.
Abstract: We theoretically study dynamic properties of thin ferromagnetic films in contact with normal metals. Moving magnetizations cause a flow of spins into adjacent conductors, which relax by spin flip, scatter back into the ferromagnet, or are absorbed by another ferromagnet. Relaxation of spins outside the moving magnetization enhances the overall damping of the magnetization dynamics in accordance with the Gilbert phenomenology. Transfer of spins between different ferromagnets by these nonequilibrium spin currents leads to a long-ranged dynamic exchange interaction and collective excitation modes. Our predictions agree well with recent ferromagnetic-resonance experiments on ultrathin magnetic films.
22 citations
TL;DR: An experimental setup is proposed to measure the spin echo in electron transport through layered ferromagnetic-normal-ferromagnetic metal structures, which resembles the spin-echo effect in the magnetization of nuclei under pulsed excitations.
Abstract: We predict a spin echo in electron transport through layered ferromagnetic-normal-ferromagnetic metal structures: whereas a spin current polarized perpendicular to the magnetization direction decays when traversing a single homogeneous ferromagnet on the scale of the ferromagnetic spin-coherence length, it partially reappears by adding a second identical but antiparallel ferromagnet. This reentrant transverse spin current resembles the spin-echo effect in the magnetization of nuclei under pulsed excitations. We propose an experimental setup to measure the spin echo.
18 citations
TL;DR: In this paper, the authors theoretically study dynamic properties of thin ferromagnetic films in contact with normal metals, and they show that spin flips outside the moving magnetization enhances the overall damping of the magnetization dynamics in accordance with the Gilbert phenomenology.
Abstract: We theoretically study dynamic properties of thin ferromagnetic films in contact with normal metals. Moving magnetizations cause a flow of spins into adjacent conductors, which relax by spin flip, scatter back into the ferromagnet, or are absorbed by another ferromagnet. Relaxation of spins outside the moving magnetization enhances the overall damping of the magnetization dynamics in accordance with the Gilbert phenomenology. Transfer of spins between different ferromagnets by these nonequilibrium spin currents leads to a long-ranged dynamic exchange interaction and novel collective excitation modes. Our predictions agree well with recent ferromagnetic-resonance experiments on ultrathin magnetic films.
TL;DR: In this article, a renormalization of the conventional and spin-mixing conductance parameters is proposed for non-collinear magnetic nanostructures in two and multiterminal structures.
Abstract: Magnetoelectronics is mainly digital, i.e. governed by up and down magnetizations. In contrast, analogue magnetoelectronics makes use of phenomena occuring for non-collinear magnetization configurations. Here we review theories which have recently been applied to the transport in non-collinear magnetic nanostructures in two and multiterminal structures, viz. random matrix and circuit theory. Both are not valid for highly transparent systems in a resistive environment like perpendicular metallic spin valves. The solution to this problem is a renormalization of the conventional and spin-mixing conductance parameters.
TL;DR: In this paper, a 3D calculation of atmospheric neutrino fluxes using accurate models of the geomagnetic field, hadronic interactions, tracking and decays is presented for the Super-Kamiokande and Sudbury Neutrino Observatory sites using the GEANT-FLUKA hadronic code.
01 Jan 2003
TL;DR: In this article, a renormalization of the conventional and spin-mixing conductance parameters is proposed for non-collinear magnetic nanostructures in two and multiterminal structures.
Abstract: Magnetoelectronics is mainly digital, i.e. governed by up and down magnetizations. In contrast, analogue magnetoelectronics makes use of phenomena occuring for non-collinear magnetization configurations. Here we review theories which have recently been applied to the transport in non-collinear magnetic nanostructures in two and multiterminal structures, viz. random matrix and circuit theory. Both are not valid for highly transparent systems in a resistive environment like perpendicular metallic spin valves. The solution to this problem is a renormalization of the conventional and spin-mixing conductance parameters.
TL;DR: In this article, the spin current and spin bias for different material combinations were estimated for different combinations of ferromagnetic resonance and Ohmic contacts, irrespective of a conductance mismatch with, for example, doped semiconductors.
Abstract: Precessing ferromagnets are predicted to inject a spin current into adjacent conductors via Ohmic contacts, irrespective of a conductance mismatch with, for example, doped semiconductors. This opens the way to create a pure spin source (``spin battery'') by the ferromagnetic resonance. We estimate the spin current and spin bias for different material combinations.
01 Jan 2003
TL;DR: In this article, the interplay between electron spin and charge in nanoscale transport phenomena is discussed, and a mechanism that explains the excess damping and dynamic exchange interactions which are observed in ferromagnet/paramagnet hybrids is proposed.
Abstract: The general theme in this thesis is the interplay between electron spin and charge in nanoscale transport phenomena. The main presentation is divided into three independent chapters. In chapter 2, we propose a mechanism that explains the excess damping and dynamic exchange interactions which are observed in ferromagnet/paramagnet hybrids. A moving ferromagnetic magnetization emits spin current into adjacent conductors, exerting a relaxation torque and transferring angular momentum out of the ferromagnet. This spin angular momentum can scatter back, relax in a nonmagnetic spacer, or be absorbed by a second ferromagnet. In the first case, the macroscopic magnetization dynamics is not affected; in the second case, the magnetization motion is nonlocally damped by spin-flip scattering processes in the spacer; and in the latter case, the two ferromagnets become dynamically coupled by an exchange of itinerant spins, resulting in collective excitation modes. This relaxation and coupling can be large and, in some cases, dominant over other mechanisms in ultrathin films and nanoparticles. Chapter 3 is devoted to studying electronic transfer in tunnel-coupled quantum wires of exceptional quality, fabricated at the cleaved edge of a GaAs/AlGaAs bilayer heterostructure. Tunneling between such wires depends on the one-electron confinement profiles along the wires as well as on electron-electron interactions in the system.
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TL;DR: In this paper, the spin-charge separation in the tunneling spectrum of a system consisting of two quantum wires connected by a long narrow tunnel junction at the edge of a GaAs/AlGaAs bilayer heterostructure is investigated.
Abstract: We present evidence for spin-charge separation in the tunneling spectrum of a system consisting of two quantum wires connected by a long narrow tunnel junction at the edge of a GaAs/AlGaAs bilayer heterostructure. Multiple excitation velocities are detected in the system by tracing out electron spectral peaks in the conductance dependence on the applied voltage, governing the energy of tunneled electrons, and the magnetic field, governing the momentum shift along the wires. The boundaries of the wires are important and lead to a characteristic interference pattern in measurements on short junctions. We show that the experimentally observed modulation of the conductance oscillation amplitude as a function of the voltage bias can also be accounted for by spin-charge separation of the elementary excitations in the interacting wires.