Unadulterated Spin Currents by means of Non-Local Injection and Spin Pumping

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turn charge 10 nm Pure Spin Currents through Non-Local Injection and Spin Pumping Axel Hoffmann Materials Science Division and Center for Nanoscale Materials Argonne National Laboratory

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Thanks to Goran Mihajlović, Oleksandr Mosendz, Yi Ji, John E. Pearson, Frank Y. Fradin, J. Sam Jiang, and Sam D. Bader Materials Science Division and Center for Nanoscale Materials Argonne National Laboratory Miguel A. Garcia Departamento F ísica de Materiales, Universidad Complutense de Madrid Gerrit E. W. Bauer Kavli Institute of NanoScience, Delft University of Technology Peter Fischer and Mi-Young Im Center for X-beam Optics, Lawrence Berkeley National Laboratory $$$ Financial Support $$$ DOE-BES

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I V 1 m turn charge 10 nm Outline Why Pure Spin Currents? Electrical Injection Spin Hall Effect Spin Pumping Conclusions

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New Physics Nobel Prize Novel Devices Spintronics Putting into Electronics

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Moving Spins Spin Dynamics Charge versus Turn Currents Charge Spin No Need for Moving Spin: Potential for Low Power Dissipation! J. Shi, et al. , Phys. Rev. Lett. 96 , 076604 (2006).

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Courtesy Claude Chappert, Universit é Paris Sud

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New Goal: Take the Charge out of Spintronics!

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Can we produce unadulterated turn streams in paramagnetic materials? YES !!! Non-neighborhood geometries Spin-subordinate diffusing (Spin-Hall) Spin pumping

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V e-or First Experimental Demonstrations I + I - V Bulk Al:  s = 450 m (4.2 K) 0 Collector Cu film:  s = 1 m (4.2 K) M. Johnson and R. H. Silsbee, Phys. Rev. Lett. 55 , 1790 (1985) Jedema et al. , Nature 410 , 345 (2001) Pure Spin Currents: The Johnson Transistor N M. Johnson and R. H. Silsbee, Phys. Rev. Lett. 55 , 1790 (1985) M. Johnson, Science 260 , 320 (1993) L F 1 F 2 F 2 F2 F1 N Emitter Base

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 s = 63  15 nm In gold at 10 K Lateral Spin-Valve with Gold a.c. current source Lock-in discovery Y. Ji, et al. , Appl. Phys. Lett. 85 , 6218 (2004)

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Lateral Spin-Valve with Copper Shadow Evaporation SEM Image Finished Device 500 nm Y. Ji, et al. , Appl. Phys. Lett. 88 , 052509 (2006)

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Spin Diffusion Length in Copper P = 7% T = 10 K Y. Ji, et al. , Appl. Phys. Lett. 88 , 052509 (2006)

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Spin-Signal at Room Temperature Co/Cu Lateral Spin-Valve L = 300 nm, T = 10 K L = 350 nm, T = 300 K  s ≈ 110 nm at room temperature

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Spin Hall Effect Spin-subordinate dispersing offers ascend to transverse turn unevenness of charge streams J. E. Hirsch, Phys. Rev. Lett. 83 , 1834 (1999) M. I. Dyakonov and V. I. Perel, JETP Lett. 13 , 467 (1971) Direct perception in GaAs with optical discovery Y. K. Kato et al. , Science 306 , 1910 (2004)

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- Spin-Skew Scattering B E + core electron

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Spin Hall versus Opposite Spin Hall Spin Hall Charge Current  Transverse Spin Imbalance Inverse Spin Hall Spin Current  Transverse Charge Imbalance Spin Dependent Scattering

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turn Hall conductivity charge conductivity more grounded turn circle cooperation bigger Importance: understanding the impact of SO coupling on electron transport perceiving materials for spintronics applications Goal: analyses to evaluate Spin Hall Angle

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Quantifying Spin Hall Angle in Metals Ferromagnetic reverberation: Magnetotransport estimations: T. Kimura et al., PRL 98 , 156601 (2007) E. Saitoh et al., APL 88 , 182509 (2006) Pt: = 0.0037 S. O. Valenzuela & M. Tinkham, Nature 442, 176 (2006) K. Ando et al., PRL 101 , 036601 (2008) Al: = 0.0001-0.0003 Pt: = 0.08 T. Seki et al., Nature Mater. 7, 125 (2008) Au: = 0.113 Large errors in  values ! Ferromagnets constantly used to create/recognize turn streams need to know turn polarization productivity at injector/identifier conceivable spurious signs: Hall, Anomalous Hall, MR How about Spin Hall impacts without ferromagnets!

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Direct Spin Hall Effect Generate Pure Spin Current Inverse Spin Hall Effect Detect Pure Spin Current Charge Current Teleportation E. M. Hankiewicz et al., Phys. Rev. B 70, 241301(R) (2004) J.E. Hirsch, Phys. Rev. Lett. 83 , 1834 (1999) D. A. Abanin et al., Phys. Rev. B 79, 035304 (2009) M. I. Dyakonov, Phys. Rev. Lett. 99 , 126601 (2007) Theoretical Idea: Use Spin Hall Effects Twice! L

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w = 110 nm t = 60 nm 1 µm Gold Hall Bar Structures Spin Hall Angle in Gold: < 0.02 Too little to be for all intents and purposes valuable! 5 μ m Mihajlović et al. , Phys. Rev. Lett. 103 , 166601 (2009)

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Unusual Application of Spin Dynamics As found in: Queen Victoria Pub, Durham, U. K.

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F N I S Spin Pumping Ferromagnetic Resonance brings about time-subordinate interfacial turn gathering This turn amassing diffuses far from the interface Results in net dc turn current opposite to interface Additional turn current offers ascend to extra damping Quantify turn current from linewidth expanding

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Combine Spin Pumping and Inverse Hall Effect Use Spin Pumping to Generate Pure Spin Current Quantify Spin Current from FMR Measured Voltage Directly Determines Spin Hall Conductivity Key Advantage: Signal Scales with Device Dimension

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Determine Spin Hall Angle for Many Materials Pt Au Mo = 0.0120 ±0.0001 = 0.0025 ±0.0006 = - 0.00096 ±0.00007 Technique effortlessly adjusted to any material!

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Can we Image Spin Accumulation Directly? What about X-beam Dichroism? Picture at Cu L-edge Magnetic Difference Images Mosendz et al. , Phys. Rev. B 80 , 104439 (2009)

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Is There Any Hope for X-Rays? Ferromagnet (i.e., ordinary TM) Spin Accumulation E d s N(E) N(E) Contrast because of various thickness of states at Fermi-level Contrast because of turn part? Well underneath 1 meV!

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I V 1 m turn charge 10 nm Conclusions Spin Currents carry on various contrasted with Charge Currents Possibility of Reduced Power Dissipation Non-Local Electrical Injection Generate Pure Spin Currents Study Spin Relaxation Spin Hall Effects Generate and Detect Spin Currents w/o Ferromagnets Spin Pumping Generate Spin Currents w/o Electric Charge Currents