Spin Backflow and ac Voltage Generation by Spin Pumping and the Inverse Spin Hall Effect

Jiao, HuJun; Bauer, G.

doi:10.1103/physrevlett.110.217602

Cited by 219 publications

(205 citation statements)

References 51 publications

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“…At the ferromagnetic insulator/normal metal interface, this spin current exerts an oscillating spin transfer torque on the magnetization [16] that can drive a magnetization precession. An effective magnetic field can be employed to parametrize the (anti-)damping torque [21] [25] with the spin diffusion length λ, electrical resistivity ρ in the normal metal, and the spin mixing interface conductance G ↑↓ (in units of −1 m −2 ). Conversely, when magnetization dynamics in the ferromagnet are excited, the normal metal provides an additional magnetization damping channel, a process which can be described as injection of a pure spin current from the ferromagnet into the normal metal.…”

Section: Theorymentioning

confidence: 99%

Current-induced spin torque resonance of a magnetic insulator

et al. 2015

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We report the observation of current-induced spin torque resonance in yttrium iron garnet/platinum bilayers. An alternating charge current at GHz frequencies in the platinum gives rise to dc spin pumping and spin Hall magnetoresistance rectification voltages, induced by the Oersted fields of the ac current and the spin Hall effect-mediated spin transfer torque. In ultrathin yttrium iron garnet films, we observe spin transfer torque actuated magnetization dynamics which are significantly larger than those generated by the ac Oersted field. Spin transfer torques thus efficiently couple charge currents and magnetization dynamics also in magnetic insulators, enabling charge current-based interfacing of magnetic insulators with microwave devices.

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Section: Theorymentioning

confidence: 99%

Current-induced spin torque resonance of a magnetic insulator

et al. 2015

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“…The spin pumping from the antiferromagnetic insulator causes a spin accumulation in the normal metal, which in turn produces a spin backflow current [11]. In antiferromagnetic insulators, the backflow spin currents within the sublattices add constructively [20,28]:…”

mentioning

confidence: 99%

“…Inside the conductor, the resulting spin accumulation and currents give insight into the spin-orbit coupling. The inverse spin Hall effect (ISHE) is often used to convert the pure spin current into a charge current, which is detected [10,11]. Additionally, the induced nonequilibrium spins can be probed with x-ray magnetic circular dichroism measurements [12,13].…”

mentioning

confidence: 99%

“…The boundary conditions for μ N s require that the spin current vanishes at the outer edge of the normal metal (y = d N ) and that the current is continuous across the antiferromagnet-normal metal interface (y = 0). The diffusion equation can be solved in position-frequency space [11,29] in terms of the Fourier components of the total spin current I N s = I p s + I b s at y = 0. The spin current in the normal metal causes a charge current perpendicular to the spin current's direction and polarization through the ISHE.…”

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Spin pumping and inverse spin Hall voltages from dynamical antiferromagnets

Johansen

Brataas

2017

Phys. Rev. B

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Dynamical antiferromagnets can pump spins into adjacent conductors. The high antiferromagnetic resonance frequencies represent a challenge for experimental detection, but magnetic fields can reduce these resonance frequencies. We compute the ac and dc inverse spin Hall voltages resulting from dynamical spin excitations as a function of a magnetic field along the easy axis and the polarization of the driving ac magnetic field perpendicular to the easy axis. We consider the insulating antiferromagnets MnF 2 , FeF 2 , and NiO. Near the spin-flop transition, there is a significant enhancement of the dc spin pumping and inverse spin Hall voltage for the uniaxial antiferromagnets MnF 2 and FeF 2 . In the uniaxial antiferromagnets it is also found that the ac spin pumping is independent of the external magnetic field when the driving field has the optimal circular polarization. In the biaxial NiO, the voltages are much weaker, and there is no spin-flop enhancement of the dc component. DOI: 10.1103/PhysRevB.95.220408 Spin pumping is a versatile tool for probing spin dynamics in ferromagnets [1][2][3][4][5][6]. The magnitude of the pumped spin currents reveals information about the magnetization dynamics and the electron-magnon coupling at interfaces [7][8][9]. The precessing spins generate a pure spin flow into adjacent conductors. Inside the conductor, the resulting spin accumulation and currents give insight into the spin-orbit coupling. The inverse spin Hall effect (ISHE) is often used to convert the pure spin current into a charge current, which is detected [10,11]. Additionally, the induced nonequilibrium spins can be probed with x-ray magnetic circular dichroism measurements [12,13].Antiferromagnets differ strikingly from ferromagnets [14]. There are no stray fields in antiferromagnets, making them more robust against the influence of external magnetic fields. The recent discovery of anisotropic magnetoresistance [15][16][17], spin-orbit torques [18], and electrical switching of an antiferromagnet [19] demonstrate the feasibility of antiferromagnets as active spintronics components.The real benefit of antiferromagnets is that they can enable terahertz circuits. Unlike ferromagnets, the resonance frequency of antiferromagnets is also governed by the tremendous exchange energy. We recently demonstrated that the transverse spin conductance, a governing factor of spin pumping, is as large in antiferromagnet-normal metal junctions (AF|N) as in ferromagnet-normal metal junctions [20]. Furthermore, this result is valid even when the magnetic system is insulating. The firm electron-magnon coupling at the interface opens the door for electrical probing of the ultrafast spin dynamics in antiferromagnets [20,21].Precessing spins in antiferromagnets generate terahertz currents in adjacent conductors. This ability opens new territory in high-frequency spintronics. Such studies could become influential in gathering vital insight into fast electron dynamics and eventually for a broad range of applications. These electric sign...

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“…where g ↑↓ eff is the effective spin-mixing conductance including a back-flow correction [48] and/or spin-orbit coupling at the interface [49]. Its averaged dc component reads…”

Section: Spin Pumping and Spin Seebeck Effectsmentioning

confidence: 99%

Energy repartition in the nonequilibrium steady state

2017

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The concept of temperature in nonequilibrium thermodynamics is an outstanding theoretical issue. We propose an energy repartition principle that leads to a spectral (mode-dependent) temperature in steady-state nonequilibrium systems. The general concepts are illustrated by analytic solutions of the classical Heisenberg spin chain connected to Langevin heat reservoirs with arbitrary temperature profiles. Gradients of external magnetic fields are shown to localize spin waves in a Wannier-Zeemann fashion, while magnon interactions renormalize the spectral temperature. Our generic results are applicable to other thermodynamic systems such as Newtonian liquids, elastic solids, and Josephson junctions.

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Spin Backflow and ac Voltage Generation by Spin Pumping and the Inverse Spin Hall Effect

Cited by 219 publications

References 51 publications

Current-induced spin torque resonance of a magnetic insulator

Current-induced spin torque resonance of a magnetic insulator

Spin pumping and inverse spin Hall voltages from dynamical antiferromagnets

Energy repartition in the nonequilibrium steady state

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