Search results for "spin pumping"
showing 10 items of 15 documents
Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/nonmagnetic metal/ferromagnet multilayered stacks
2017
In this work we focus on magnetic relaxation in Mn80Ir20(12 nm)/Cu(6 nm)/Py(dF) antiferromagnet/Cu/ferromagnet (AFM/Cu/FM) multilayers with different thickness of the ferromagnetic permalloy layer. An effective FM-AFM interaction mediated via the conduction electrons in the nonmagnetic Cu spacer – the spin-pumping effect – is detected as an increase in the linewidth of the ferromagnetic resonance (FMR) spectra and a shift of the resonant magnetic field. We further find experimentally that the spin-pumping-induced contribution to the linewidth is inversely proportional to the thickness of the Py layer. We show that this thickness dependence likely originates from the dissipative dynamics of …
Enhancement of the Spin Pumping Effect by Magnon Confluence Process in YIG/Pt Bilayers
2019
The experimental investigation of the spin pumping process by dipolar‐exchange magnons parametrically excited in in‐plane magnetized yttrium iron garnet/platinum bilayers is presented. The electric voltage generated in the platinum layer via the inverse spin Hall effect (ISHE) results from contributions of two opposite spin currents formed by the longitudinal spin Seebeck effect and by the spin pumping from parametric magnons. In the field‐dependent measurements of the spin pumping‐induced component of the ISHE‐voltage, a clearly visible sharp peak is detected at high pumping powers. It is found that the peak position is determined by the process of confluence of two parametrically excited …
Cross-sublattice Spin Pumping and Magnon Level Attraction in van der Waals Antiferromagnets
2020
We theoretically study spin pumping from a layered van der Waals antiferromagnet in its canted ground state into an adjacent normal metal. We find that the resulting dc spin pumping current bears contributions along all spin directions. Our analysis allows for detecting intra- and cross-sublattice spin-mixing conductances via measuring the two in-plane spin current components. We further show that sublattice symmetry-breaking Gilbert damping can be realized via interface engineering and induces a dissipative coupling between the optical and acoustic magnon modes. This realizes magnon level attraction and exceptional points in the system. Furthermore, the dissipative coupling and cross-subla…
Spin Pumping and Torque Statistics in the Quantum Noise Limit
2016
We analyze the statistics of charge and energy currents and spin torque in a metallic nanomagnet coupled to a large magnetic metal via a tunnel contact. We derive a Keldysh action for the tunnel barrier, describing the stochastic currents in the presence of a magnetization precessing with the rate $\Omega$. In contrast to some earlier approaches, we include the geometric phases that affect the counting statistics. We illustrate the use of the action by deriving spintronic fluctuation relations, the quantum limit of pumped current noise, and consider the fluctuations in two specific cases: the situation with a stable precession of magnetization driven by spin transfer torque, and the torque-…
Femtosecond formation dynamics of the spin Seebeck effect revealed by terahertz spectroscopy
2018
Understanding the transfer of spin angular momentum is essential in modern magnetism research. A model case is the generation of magnons in magnetic insulators by heating an adjacent metal film. Here, we reveal the initial steps of this spin Seebeck effect with <27fs time resolution using terahertz spectroscopy on bilayers of ferrimagnetic yttrium-iron garnet and platinum. Upon exciting the metal with an infrared laser pulse, a spin Seebeck current $j_\textrm{s}$ arises on the same ~100fs time scale on which the metal electrons thermalize. This observation highlights that efficient spin transfer critically relies on carrier multiplication and is driven by conduction electrons scattering …
Large enhancement of spin pumping due to the surface bound states in normal metal/superconductor structures
2020
We show that the spin pumping from ferromagnetic insulator into the adjacent metallic spin sink can be strongly stimulated by the superconducting correlations. The key physical mechanism responsible for this effect is the presence of Andreev bound states at the ferromagnetic insulator/superconductor interface. We consider the minimal model when these states appear because of the suppressed pairing constant within the interfacial normal layer. For thin normal layers we obtain a strongly peaked temperature dependence of the Gilbert damping coefficient which has been recently observed in such systems. For thicker normal layers the Gilbert damping monotonically increases down to the temperature…
Tuning Spin Current Injection at Ferromagnet-Nonmagnet Interfaces by Molecular Design.
2020
There is a growing interest in utilizing the distinctive material properties of organic semiconductors for spintronic applications. Here, we explore the injection of pure spin current from Permalloy into a small molecule system based on dinaphtho[2,3-b:2,3-f]thieno[3,2-b]thiophene (DNTT) at ferromagnetic resonance. The unique tunability of organic materials by molecular design allows us to study the impact of interfacial properties on the spin injection efficiency systematically. We show that both the spin injection efficiency at the interface and the spin diffusion length can be tuned sensitively by the interfacial molecular structure and side chain substitution of the molecule.
Spin pumping and measurement of spin currents in optical superlattices
2016
We report on the experimental implementation of a spin pump with ultracold bosonic atoms in an optical superlattice. In the limit of isolated double wells, it represents a 1D dynamical version of the quantum spin Hall effect. Starting from an antiferromagnetically ordered spin chain, we periodically vary the underlying spin-dependent Hamiltonian and observe a spin current without charge transport. We demonstrate a novel detection method to measure spin currents in optical lattices via superexchange oscillations emerging after a projection onto static double wells. Furthermore, we directly verify spin transport through in situ measurements of the spins' center-of-mass displacement.
Spin pumping in noncollinear antiferromagnets
2021
The ac spin pumping of noncollinear antiferromagnets is theoretically investigated. Starting from an effective action description of the spin system, we derive the Onsager coefficients connecting the spin pumping and spin-transfer torque associated with the dynamics of the SO(3)-valued antiferromagnetic order parameter. Our theory is applied to a kagome antiferromagnet resonantly driven by a uniform external magnetic field. We demonstrate that the reactive (dissipative) spin-transfer torque parameter can be extracted from the pumped ac spin current in-phase (in quadrature) with the driving field. Furthermore, we find that the three spin-wave bands of the kagome AF generate spin currents wit…
Thickness and power dependence of the spin-pumping effect inY3Fe5O12/Pt heterostructures measured by the inverse spin Hall effect
2015
The dependence of the spin-pumping effect on the yttrium iron garnet $({\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$, YIG) thickness detected by the inverse spin Hall effect (ISHE) has been investigated quantitatively. Due to the spin-pumping effect driven by the magnetization precession in the ferrimagnetic insulator ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ film a spin-polarized electron current is injected into the Pt layer. This spin current is transformed into electrical charge current by means of the ISHE. An increase of the ISHE voltage with increasing film thickness is observed and compared to the theoretically expected behavior. The effective damping parameter of t…