Spin-scattering rates in metallic thin films measured by ferromagnetic resonance damping enhanced by spin-pumping

Boone, Carl; Shaw, Justin M.; Nembach, Hans T.; Silva, T. J.

doi:10.1063/1.4922581

Cited by 60 publications

(60 citation statements)

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“…Our theory is corroborated by recent experiments in ultrathin films [20,21]. We propose that an experiment to verify our predictions can be based on laser-pulse, pumpprobe experiments (probing the Faraday or Kerr rotation) with femtosecond temporal resolution in films of varying thickness [40,41].…”

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confidence: 68%

“…The DP mechanism (that we briefly describe below) is known to be important in III-V or II-VI semiconductors or semiconductor heterostructures due to their inversion asymmetry [18,19], but, to our knowledge, it has been largely overlooked so far in the important case of supported films or metallic bilayers, which show manifestly no inversion symmetry. Only recently, data from spin-pumping [20] and weak antilocalization [21] experiments in ultrathin films were found to fit the DP and not the EY mechanism.…”

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confidence: 99%

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Strong spin-orbit fields and Dyakonov-Perel spin dephasing in supported metallic films

et al. 2016

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Spin dephasing by the Dyakonov-Perel mechanism in metallic films deposited on insulating substrates is revealed, and quantitatively examined by means of density functional calculations combined with a kinetic equation. The surface-to-substrate asymmetry, probed by the metal wave functions in thin films, is found to produce strong spin-orbit fields and a fast Larmor precession, giving a dominant contribution to spin decay over the Elliott-Yafet spin relaxation up to a thickness of 70 nm. The spin dephasing is oscillatory in time with a rapid (subpicosecond) initial decay. However, parts of the Fermi surface act as spin traps, causing a persistent tail signal lasting 1000 times longer than the initial decay time. It is also found that the decay depends on the direction of the initial spin polarization, resulting in a spin-dephasing anisotropy of 200% in the examined cases. DOI: 10.1103/PhysRevB.94.180406 In spintronics experiments, spins are often excited in, or transported through, nonmagnetic metallic thin film media [1]. Typical examples are Cu, Au, or Pt, used in spin-current creation or detection via the spin Hall effect [2][3][4][5] or spin Nernst effect [6,7]. Paramount for the spin-transport properties of a medium is the characteristic time T after which the outof-equilibrium spin population that was created in the medium is lost by relaxation or dephasing [8,9]. The microscopic mechanisms leading to spin reduction depend on the material properties, and it is commonly accepted that the Elliott-Yafet (EY) mechanism [10,11] is dominant in metals [12][13][14][15], since they show space-inversion symmetry [16]. However, any substrate on which the film is deposited breaks the inversion symmetry; if the film is thin enough (thinner than the electron phase relaxation length), the resulting asymmetry is felt by the metallic states extending over the film thickness, even though the substrate and surface potential are screened in the film interior. In this case, as we argue in this Rapid Communication, the band structure changes throughout the film and the Dyakonov-Perel (DP) mechanism [17] for spin dephasing is activated and becomes the dominant cause of spin reduction. The DP mechanism (that we briefly describe below) is known to be important in III-V or II-VI semiconductors or semiconductor heterostructures due to their inversion asymmetry [18,19], but, to our knowledge, it has been largely overlooked so far in the important case of supported films or metallic bilayers, which show manifestly no inversion symmetry. Only recently, data from spin-pumping [20] and weak antilocalization [21] experiments in ultrathin films were found to fit the DP and not the EY mechanism.Characteristic of systems with spin-orbit coupling and timereversal symmetry but broken inversion symmetry is the lifting of conjugation degeneracy [11] at each crystal momentum k and energy E k of the band structure. The resulting pair of states where σ is the vector of Pauli matrices and the vector quantity k is called the spin-orbit field (SOF) ...

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confidence: 99%

Strong spin-orbit fields and Dyakonov-Perel spin dephasing in supported metallic films

et al. 2016

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“…(3). The effective spin mixing conductance contains details of the spin transport in the adjacent nonmagnetic layers, such as the interfacial spin mixing conductance, both the conductivity and spin diffusion for all the nonmagnetic layers with a nonnegligible spin accumulation, as well as the details of the spatial profile for the net spin accumulation [51,52]. The values of g ↑↓ eff are plotted versus the alloy concentration in Fig.…”

Section: Resultsmentioning

confidence: 99%

Magnetic properties in ultrathin 3d transition-metal binary alloys. II. Experimental verification of quantitative theories of damping and spin pumping

et al. 2017

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General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. A systematic experimental study of Gilbert damping is performed via ferromagnetic resonance for the disordered crystalline binary 3d transition-metal alloys Ni-Co, Ni-Fe, and Co-Fe over the full range of alloy compositions. After accounting for inhomogeneous linewidth broadening, the damping shows clear evidence of both interfacial damping enhancement (by spin pumping) and radiative damping. We quantify these two extrinsic contributions and thereby determine the intrinsic damping. The comparison of the intrinsic damping to multiple theoretical calculations yields good qualitative and quantitative agreement in most cases. Furthermore, the values of the damping obtained in this study are in good agreement with a wide range of published experimental and theoretical values. Additionally, we find a compositional dependence of the spin mixing conductance.

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“…The inverse of the prefactor, i.e., 2Re[G eff ↑↓ ]/(σ/λ), is introduced as the spin current 'transmissivity', T. According to Eq. (7), T is very sensitive to the spin diffusion length, which in itself is a material-dependent parameter that requires careful calibration for many spin Hall metals 22,[48][49][50][51][52][53] . Increasing the spin diffusion length linearly enhances the value of T and decreases the value of θ …”

Section: Dc-tuned Damping Analysismentioning

confidence: 99%

All-electrical manipulation of magnetization dynamics in a ferromagnet by antiferromagnets with anisotropic spin Hall effects

et al. 2015

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We investigate spin-orbit torques of metallic CuAu-I-type antiferromagnets using spin-torque ferromagnetic resonance tuned by a dc-bias current. The observed spin torques predominantly arise from diffusive transport of spin current generated by the spin Hall effect. We find a growth-orientation dependence of the spin torques by studying epitaxial samples, which may be correlated to the anisotropy of the spin Hall effect. The observed anisotropy is consistent with first-principles calculations on the intrinsic spin Hall effect. Our work demonstrates large tunable spin-orbit effects in magnetically-ordered materials.

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Spin-scattering rates in metallic thin films measured by ferromagnetic resonance damping enhanced by spin-pumping

Cited by 60 publications

References 85 publications

Strong spin-orbit fields and Dyakonov-Perel spin dephasing in supported metallic films

Strong spin-orbit fields and Dyakonov-Perel spin dephasing in supported metallic films

Magnetic properties in ultrathin 3d transition-metal binary alloys. II. Experimental verification of quantitative theories of damping and spin pumping

All-electrical manipulation of magnetization dynamics in a ferromagnet by antiferromagnets with anisotropic spin Hall effects

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