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Yoshichika Otani - One of the best experts on this subject based on the ideXlab platform.
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evaluation of Spin Diffusion length and Spin hall angle of the antiferromagnetic weyl semimetal mn 3 sn
Physical Review B, 2019Co-Authors: P K Muduli, Kouta Kondou, Tomoya Higo, T Nishikawa, Hironari Isshiki, Daisuke Nishiohamane, Satoru Nakatsuji, Yoshichika OtaniAbstract:The antiferromagnetic Weyl semimetal ${\mathrm{Mn}}_{3}\mathrm{Sn}$ has been shown to generate strong intrinsic anomalous Hall effect (AHE) at room temperature, due to large momentum-space Berry curvature from the time-reversal symmetry-breaking electronic bands of the Kagome planes. This prompts us to investigate intrinsic Spin Hall effect, a transverse phenomenon with identical origin as the intrinsic AHE. We report inverse Spin Hall effect experiments in nanocrystalline ${\mathrm{Mn}}_{3}\mathrm{Sn}$ nanowires at room temperature using Spin absorption method, which enables us to quantitatively derive both the Spin Diffusion length and the Spin Hall angle in the same device. We observed clear absorption of the Spin current in the ${\mathrm{Mn}}_{3}\mathrm{Sn}$ nanowires when kept in contact with the Spin transport channel of a lateral Spin-valve device. We estimate Spin Diffusion length ${\ensuremath{\lambda}}_{s({\text{Mn}}_{3}\text{Sn})}\ensuremath{\sim}0.75$ $\ifmmode\pm\else\textpm\fi{}$ 0.67 nm from the comparison of Spin signal of an identical reference lateral Spin valve without ${\mathrm{Mn}}_{3}\mathrm{Sn}$ nanowire. From inverse Spin Hall measurements, we evaluate Spin Hall angle ${\ensuremath{\theta}}_{\text{SH}}\ensuremath{\sim}5.3$ $\ifmmode\pm\else\textpm\fi{}$ 2.4 $%$ and Spin Hall conductivity ${\ensuremath{\sigma}}_{\text{SH}}\ensuremath{\sim}46.99$ $\ifmmode\pm\else\textpm\fi{}$ 20.63 $\left(\frac{\ensuremath{\hbar}}{e}\right){(\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm})}^{\ensuremath{-}1}$. The estimated Spin Hall conductivity agrees with both in sign and magnitude to the theoretically predicted intrinsic ${\ensuremath{\sigma}}_{\text{SH}}^{\text{int}}\ensuremath{\sim}36$-96 ($\ensuremath{\hbar}/e$) (${\mathrm{\ensuremath{\Omega}}\phantom{\rule{4pt}{0ex}}\mathrm{cm})}^{\ensuremath{-}1}$. We also observed anomalous Hall effect at room temperature in nano-Hall bars prepared at the same time as the Spin Hall devices. Large anomalous Hall conductivity along with adequate Spin Hall conductivity makes ${\mathrm{Mn}}_{3}\mathrm{Sn}$ a promising material for ultrafast and ultrahigh-density Spintronics devices.
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Spin Diffusion length of permalloy using Spin absorption in lateral Spin valves
arXiv: Mesoscale and Nanoscale Physics, 2019Co-Authors: Edurne Sagasta, Yasutomo Omori, Miren Isasa, Yoshichika Otani, Luis E Hueso, Felix CasanovaAbstract:We employ the Spin absorption technique in lateral Spin valves to extract the Spin Diffusion length of Permalloy (Py) as a function of temperature and resistivity. A linear dependence of the Spin Diffusion length with conductivity of Py is observed, evidencing that Elliott-Yafet is the dominant Spin relaxation mechanism in Permalloy. Completing the data set with additional data found in literature, we obtain $\lambda_{Py}= (0.91\pm 0.04) (f\Omega m^2)/\rho_{Py}$.
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Spin Diffusion length of permalloy using Spin absorption in lateral Spin valves
Applied Physics Letters, 2017Co-Authors: Edurne Sagasta, Yasutomo Omori, Miren Isasa, Yoshichika Otani, Luis E Hueso, Felix CasanovaAbstract:We employ the Spin absorption technique in lateral Spin valves to extract the Spin Diffusion length of Permalloy (Py) as a function of temperature and resistivity. A linear dependence of the Spin Diffusion length with the conductivity of Py is observed, evidencing that the Elliott-Yafet mechanism is the dominant Spin relaxation mechanism in Permalloy. Completing the dataset with additional data found in the literature, we obtain λPy = (0.91 ± 0.04) (fΩm2)/ρPy.
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experimental verification of comparability between Spin orbit and Spin Diffusion lengths
Physical Review Letters, 2013Co-Authors: Yasuhiro Niimi, Dahai Wei, Hiroshi Idzuchi, T Wakamura, Takeo Kato, Yoshichika OtaniAbstract:We experimentally confirmed that the Spin-orbit lengths of noble metals obtained from weak antilocalization measurements are comparable to the Spin Diffusion lengths determined from lateral Spin valve ones. Even for metals with strong Spin-orbit interactions such as Pt, we verified that the two methods gave comparable values which were much larger than those obtained from recent Spin torque ferromagnetic resonance measurements. To give a further evidence for the comparability between the two length scales, we measured the disorder dependence of the Spin-orbit length of copper by changing the thickness of the wire. The obtained Spin-orbit length nicely follows a linear law as a function of the Diffusion coefficient, clearly indicating that the Elliott-Yafet mechanism is dominant as in the case of the Spin Diffusion length.
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evolution of the Spin hall effect in pt nanowires size and temperature effects
Physical Review Letters, 2007Co-Authors: L Vila, Takashi Kimura, Yoshichika OtaniAbstract:: We have studied the evolution of the Spin Hall effect (SHE) in the regime where the material size responsible for the Spin accumulation is either smaller or larger than the Spin Diffusion length. Lateral Spin valve structures with Pt insertions were successfully used to measure the Spin absorption efficiency as well as the Spin accumulation in Pt induced through the Spin Hall effect. Under a constant applied current the results show a decrease of the Spin accumulation signal is more pronounced as the Pt thickness exceeds the Spin Diffusion length. This implies that the Spin accumulation originates from bulk scattering inside the Pt wire and the Spin Diffusion length limits the SHE. We have also analyzed the temperature variation of the Spin Hall conductivity to identify the dominant scattering mechanism.
B J Van Wees - One of the best experts on this subject based on the ideXlab platform.
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temperature dependence of the magnon Spin Diffusion length and magnon Spin conductivity in the magnetic insulator yttrium iron garnet
Physical Review B, 2016Co-Authors: Ludo J Cornelissen, Juan Shan, B J Van WeesAbstract:We present a systematic study of the temperature dependence of diffusive magnon Spin transport using nonlocal devices fabricated on a 210-nm yttrium iron garnet film on a gadolinium gallium garnet substrate. In our measurements, we detect Spin signals arising from electrical and thermal magnon generation, and we directly extract the magnon Spin Diffusion length ${\ensuremath{\lambda}}_{m}$ for temperatures from 2 to 293 K. Values of ${\ensuremath{\lambda}}_{m}$ obtained from electrical and thermal generation agree within the experimental error with ${\ensuremath{\lambda}}_{m}=9.6\ifmmode\pm\else\textpm\fi{}0.9\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$ at room temperature to a minimum of ${\ensuremath{\lambda}}_{m}=5.5\ifmmode\pm\else\textpm\fi{}0.7\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$ at 30 K. Using a two-dimensional finite element model to fit the data obtained for electrical magnon generation we extract the magnon Spin conductivity ${\ensuremath{\sigma}}_{m}$ as a function of temperature, which is reduced from ${\ensuremath{\sigma}}_{m}=3.7\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\times\else\texttimes\fi{}{10}^{5}\phantom{\rule{0.28em}{0ex}}\mathrm{S}/\mathrm{m}$ at room temperature to ${\ensuremath{\sigma}}_{m}=0.9\ifmmode\pm\else\textpm\fi{}0.6\ifmmode\times\else\texttimes\fi{}{10}^{4}\phantom{\rule{0.28em}{0ex}}\mathrm{S}/\mathrm{m}$ at 5 K. Finally, we observe an enhancement of the signal originating from thermally generated magnons for low temperatures where a maximum is observed around $T=7\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. An explanation for this low-temperature enhancement is however still missing and requires additional investigation.
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magnetic field dependence of the magnon Spin Diffusion length in the magnetic insulator yttrium iron garnet
Physical Review B, 2016Co-Authors: Ludo J Cornelissen, B J Van WeesAbstract:We investigated the effect of an external magnetic field on the diffusive Spin transport by magnons in the magnetic insulator Y3Fe5O12, using a nonlocal magnon transport measurement geometry. We observed a decrease in magnon Spin Diffusion length lambda(m) for increasing field strengths, where lambda(m) is reduced from 9.6 +/- 1.2 mu m at 10 mT to 4.2 +/- 0.6 mu m at 3.5 T at room temperature. In addition, we find that there must be at least one additional transport parameter that depends on the external magnetic field. Our results do not allow us to unambiguously determine whether this is the magnon equilibrium density or the magnon Diffusion constant. These results are significant for experiments in the more conventional longitudinal Spin Seebeck geometry, since the magnon Spin Diffusion length sets the length scale for the Spin Seebeck effect as well and is relevant for its understanding.
R C Myers - One of the best experts on this subject based on the ideXlab platform.
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long range pure magnon Spin Diffusion observed in a nonlocal Spin seebeck geometry
Physical Review B, 2015Co-Authors: Brandon Giles, Zihao Yang, John Jamison, R C MyersAbstract:The Spin Diffusion length for thermally excited magnon Spins is measured by utilizing a nonlocal Spin-Seebeck effect measurement. In a bulk single crystal of yttrium iron garnet (YIG) a focused laser thermally excites magnon Spins. The Spins diffuse laterally and are sampled using a Pt inverse Spin Hall effect detector. Thermal transport modeling and temperature dependent measurements demonstrate the absence of spurious temperature gradients beneath the Pt detector and confirm the nonlocal nature of the experimental geometry. Remarkably, we find that thermally excited magnon Spins in YIG travel over 120 \textmu{}m at 23 K, indicating that they are robust against inelastic scattering. The Spin Diffusion length is found to be at least 47 \textmu{}m and as high as 73 \textmu{}m at 23 K in YIG, while at room temperature it drops to less than 10 \textmu{}m. Based on this long Spin Diffusion length, we envision the development of thermally powered Spintronic devices based on electrically insulating, but Spin conducting materials.
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long range pure magnon Spin Diffusion observed in a nonlocal Spin seebeck geometry
Physical Review B, 2015Co-Authors: Brandon Giles, Zihao Yang, John S Jamison, R C MyersAbstract:The Spin Diffusion length for thermally excited magnon Spins is measured by utilizing a non-local Spin-Seebeck effect measurement. In a bulk single crystal of yttrium iron garnet (YIG) a focused laser thermally excites magnon Spins. The Spins diffuse laterally and are sampled using a Pt inverse Spin Hall effect detector. Thermal transport modeling and temperature dependent measurements demonstrate the absence of spurious temperature gradients beneath the Pt detector and confirm the non-local nature of the experimental geometry. Remarkably, we find that thermally excited magnon Spins in YIG travel over 120 $\mu$m at 23 K, indicating that they are robust against inelastic scattering. The Spin Diffusion length is found to be at least 47 $\mu$m and as high as 73 $\mu$m at 23 K in YIG, while at room temperature it drops to less than 10 $\mu$m. Based on this long Spin Diffusion length, we envision the development of thermally powered Spintronic devices based on electrically insulating, but Spin conducting materials.
Thomas J Silva - One of the best experts on this subject based on the ideXlab platform.
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determination of Spin hall effect and Spin Diffusion length of pt from self consistent fitting of damping enhancement and inverse Spin orbit torque measurements conference presentation
Spintronics XI, 2018Co-Authors: Thomas J Silva, Eric R J Edwards, Hans T Nembach, Olof Karis, Mathias Weiler, Andrew J BergerAbstract:Functional Spintronic devices rely on Spin-charge interconversion effects, such as the reciprocal processes of electric field-driven Spin torque and magnetization dynamics-driven Spin and charge flow. Both damping-like and field-like Spin-orbit torques have been observed in the forward process of current-driven Spin torque and damping-like inverse Spin-orbit torque has been well-studied via Spin pumping into heavy metal layers. Here we demonstrate that established microwave transmission spectroscopy of ferromagnet/normal metal bilayers under ferromagnetic resonance can be used to inductively detect the AC charge currents driven by the inverse Spin-charge conversion processes. This technique relies on vector network analyzer ferromagnetic resonance (VNA-FMR) measurements. We show that in addition to the commonly-extracted spectroscopic information, VNA-FMR measurements can be used to quantify the magnitude and phase of all AC charge currents in the sample, including those due to Spin pumping and Spin-charge conversion. Our findings reveal that Permalloy/Pt bilayers exhibit both damping-like and field-like inverse Spin-orbit torques. While the magnitudes of both the damping-like and field-like inverse Spin-orbit torque are of comparable scale to prior reported values for similar material systems, we observed a significant dependence of the damping-like magnitude on the order of deposition. This suggests interface quality plays an important role in the overall strength of the damping-like Spin-to-charge conversion. Spin memory loss (SML) [1] and proximity-induced magnetic moments at the FM/NM interface [2] have been invoked to explain the large damping enhancement caused by thin NM films even when the NM thickness is less than its Spin Diffusion length. In this model, Spin loss at the FM/NM interface acts as an additional parallel Spin relaxation pathway to that of Spin pumping and Diffusion into the Pt bulk. From damping measurements alone, the relative contributions of these mechanisms are not resolvable. In this work, we show that a self-consistent fit of Gilbert damping and damping-like iSOT versus Pt thickness—where both sets of data are described by the same Spin Diffusion length—makes it possible to separate these sources of damping. Furthermore, this data analysis methodology allows for unambiguous determination of the Spin-mixing conductance at the FM/NM interface. We therefore can determine the Spin Hall conductivity (or Spin Hall angle) without having to refer to Spin transport parameters, e.g. the Spin-mixing conductance and Spin Diffusion length, as determined from measurements performed on dissimilar samples or theoretical idealized values. For our samples of Pt deposited on Permalloy, only 37 ± 6% of the total damping enhancement from the Pt film is attributable to Spin pumping into the Pt layer when the Pt thickness is much greater than the Spin Diffusion length. The self-consistent fit also results in a Spin Diffusion of length of (4.2 ± 0.1) nm, and a Spin mixing conductance of (130,000 ± 20,000) 1/(μΩ cm^2), which is in good agreement with the maximum theoretical value for Pt of 107,000 1/(μΩ cm^2) [3], given the estimated error, and σ_SH = (2.36 ± 0.04) 1/(μΩ m). This corresponds to a Spin Hall angle of 0.387 ± 0.008. While this θ_SH is among the largest reported for Pt [4, 5], it is a necessary logical conclusion that with less Spin current driven into the NM (on account of SML), a larger Spin-to-charge conversion efficiency is required to fit the data than would be otherwise obtained if the SML were negligible. We furthermore stress that the phenomenological value for the damping-like Spin orbit torque is comparable to that measured with other techniques [5-7]. This indicates that the Pt layer in our samples behaves conventionally, and stresses the importance of characterizing Spin loss mechanisms to optimize SOT for magnetic switching. REFERENCES [1] J.-C. Rojas-Sanchez, N. Reyren, P. Laczkowski, et al., "Spin Pumping and Inverse Spin Hall Effect in Platinum: The Essential Role of Spin-Memory Loss at Metallic Interfaces," Phys. Rev. Lett., vol. 112, p. 106602 (2014). [2] M. Caminale, A. Ghosh, S. Auffret, et al., "Spin pumping damping and magnetic proximity effect in Pd and Pt Spin-sink layers," Physical Review B, vol. 94, p. 014414 (2016). [3] Y. Liu, Z. Yuan, R. J. H. Wesselink, et al., "Interface Enhancement of Gilbert Damping from First Principles," Physical Review Letters, vol. 113, p. 207202 (2014). [4] W. Zhang, W. Han, X. Jiang, et al., "Role of transparency of platinum-ferromagnet interfaces in determining the intrinsic magnitude of the Spin Hall effect," Nat Phys, Article vol. 11, pp. 496-502 (2015). [5] C.-F. Pai, Y. Ou, L. H. Vilela-Leao, et al., "Dependence of the efficiency of Spin Hall torque on the transparency of Pt/ferromagnetic layer interfaces," Phys. Rev. B, vol. 92, p. 064426 (2015). [6] K. Garello, I. M. Miron, C. O. Avci, et al., "Symmetry and magnitude of Spin-orbit torques in ferromagnetic heterostructures," Nat. Nano., vol. 8, pp. 587-593 (2013). [7] M.-H. Nguyen, D. C. Ralph, and R. A. Buhrman, "Spin Torque Study of the Spin Hall Conductivity and Spin Diffusion Length in Platinum Thin Films with Varying Resistivity," Physical Review Letters, vol. 116, p. 126601 (2016).
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determination of the Spin hall effect and the Spin Diffusion length of pt from self consistent fitting of damping enhancement and inverse Spin orbit torque measurements
Physical Review B, 2018Co-Authors: Andrew J Berger, Eric R J Edwards, Hans T Nembach, Olof Karis, Mathias Weiler, Thomas J SilvaAbstract:Understanding the evolution of Spin-orbit torque (SOT) with increasing heavy-metal thickness in ferromagnet/normal metal (FM/NM) bilayers is critical for the development of magnetic memory based on SOT. However, several experiments have revealed an apparent discrepancy between damping enhancement and dampinglike SOT regarding their dependence on NM thickness. Here, using linewidth and phase-resolved amplitude analysis of vector network analyzer ferromagnetic resonance (VNA-FMR) measurements, we simultaneously extract damping enhancement and both fieldlike and dampinglike inverse SOT in ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$/Pt bilayers as a function of Pt thickness. By enforcing an interpretation of the data which satisfies Onsager reciprocity, we find that both the damping enhancement and dampinglike inverse SOT can be described by a single Spin Diffusion length $(\ensuremath{\approx}4\phantom{\rule{0.16em}{0ex}}\mathrm{nm})$, and that we can separate the Spin pumping and Spin-memory loss contributions to the total damping. This analysis indicates that less than 40% of the angular momentum pumped by FMR through the ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$/Pt interface is transported as Spin current into the Pt. On account of the Spin-memory loss and corresponding reduction in total Spin current available for Spin-charge transduction in the Pt, we determine the Pt Spin Hall conductivity $[{\ensuremath{\sigma}}_{\mathrm{SH}}=(2.36\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.28em}{0ex}}{\ensuremath{\omega}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}]$ and bulk Spin Hall angle $({\ensuremath{\theta}}_{\mathrm{SH}}=0.387\ifmmode\pm\else\textpm\fi{}0.008)$ to be larger than commonly cited values. These results suggest that Pt can be an extremely useful source of SOT if the FM/NM interface can be engineered to minimize Spin loss. Lastly, we find that self-consistent fitting of the damping and SOT data is best achieved by a model with Elliott-Yafet Spin relaxation and extrinsic inverse Spin Hall effect, such that both the Spin Diffusion length and Spin Hall conductivity are proportional to the Pt charge conductivity.
R A Buhrman - One of the best experts on this subject based on the ideXlab platform.
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Spin torque study of the Spin hall conductivity and Spin Diffusion length in platinum thin films with varying resistivity
Physical Review Letters, 2016Co-Authors: Minhhai Nguyen, D C Ralph, R A BuhrmanAbstract:We report measurements of the Spin torque efficiencies in perpendicularly magnetized Pt/Co bilayers where the Pt resistivity ρ_{Pt} is strongly dependent on thickness t_{Pt}. The dampinglike Spin Hall torque efficiency per unit current density ξ_{DL}^{j} varies significantly with t_{Pt}, exhibiting a peak value ξ_{DL}^{j}=0.12 at t_{Pt}=2.8-3.9 nm. In contrast, ξ_{DL}^{j}/ρ_{Pt} increases monotonically with t_{Pt} and saturates for t_{Pt}>5 nm, consistent with an intrinsic Spin Hall effect mechanism, in which ξ_{DL}^{j} is enhanced by an increase in ρ_{Pt}. Assuming the Elliott-Yafet Spin scattering mechanism dominates, we estimate that the Spin Diffusion length λ_{s}=(0.77±0.08)×10^{-15} Ω·m^{2}/ρ_{Pt}.
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Spin torque study of the Spin hall conductivity and Spin Diffusion length in platinum thin films with varying resistivity
Physical Review Letters, 2016Co-Authors: Minhhai Nguyen, D C Ralph, R A BuhrmanAbstract:We report measurements of the Spin torque efficiencies in perpendicularly magnetized $\mathrm{Pt}/\mathrm{Co}$ bilayers where the Pt resistivity ${\ensuremath{\rho}}_{\mathrm{Pt}}$ is strongly dependent on thickness ${t}_{\mathrm{Pt}}$. The dampinglike Spin Hall torque efficiency per unit current density ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}$ varies significantly with ${t}_{\mathrm{Pt}}$, exhibiting a peak value ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}=0.12$ at ${t}_{\mathrm{Pt}}=2.8--3.9\text{ }\text{ }\mathrm{nm}$. In contrast, ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}/{\ensuremath{\rho}}_{\mathrm{Pt}}$ increases monotonically with ${t}_{\mathrm{Pt}}$ and saturates for ${t}_{\mathrm{Pt}}g5\text{ }\text{ }\mathrm{nm}$, consistent with an intrinsic Spin Hall effect mechanism, in which ${\ensuremath{\xi}}_{\mathrm{DL}}^{j}$ is enhanced by an increase in ${\ensuremath{\rho}}_{\mathrm{Pt}}$. Assuming the Elliott-Yafet Spin scattering mechanism dominates, we estimate that the Spin Diffusion length ${\ensuremath{\lambda}}_{s}=(0.77\ifmmode\pm\else\textpm\fi{}0.08)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}\text{ }\text{ }\mathrm{\ensuremath{\Omega}}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{m}}^{2}/{\ensuremath{\rho}}_{\mathrm{Pt}}$.
