GaMnAs

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DFG Meeting Halbleiter-Spintronik
Experiments to probe the inverse Spin-Hall
Effect in GaAs U. Pfeuffer, R. Neumann,
D. Schuh, W. Wegscheider, D. Weiss 7. June 2008
University of Regensburg
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
CONTENT

• Motivation
• Spin-Hall Structure
• Sample Preparation
• Measurements
• Conclusion

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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MOTIVATION
Spin-Hall Effect Electric field induces
transverse spin-current due to spin-orbit
scattering.
Inverser Spin-Hall Effect Spincurrent induces a
transverse charge-current.
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MOTIVATION
Spin-Hall-Structure
z
FM
y
x
FM
LSH
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MOTIVATION
Valenzuela Trinkham Electrical measurements in
diffusive metallic conductor. Spincurrent
injected out of ferromagnetic CoFe through Al2O3
tunneling barrier in Al Hall-Bar. Spin
detection without magnetic materials. Spincurre
nt induces due to spin-orbit scattering a
transversve Spin-Hall imbalance ?
USH External B-field defines direction of
spins
AFM image, S.O. Valenzuela et al., Nature Lett.
442, 13 (2006)
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MOTIVATION
Valenzuela Trinkham
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
SAMPLE PREPARATION

• Material
• 3.2 Preparation
• Zn pads
• annealing _at_ 500C
• Hall-Bar
• (acetic acid)
• Au contacts
• EBL
• Fe sputtering Au
• (80nm 100nm)

Wafer D070313B (grown by D. Schuh, Workgroup W.
Wegscheider, University of Regensburg)
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Sample 1 bad sample
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Sample 1 bad sample
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Sample 1 bad sample
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Sample 1 bad sample
Change of polarization of injected current
? J. Moser et al. Appl. Phys. Lett. 89, 162106
(2006)
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Reproducibility
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Sample 2 good sample
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Sample 2 good sample
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
MEASUREMENTS
Sample 2 good sample
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
CONCLUSION OUTLOOK

• Measured signal looks like inverse
  Spin-Hall- Effect on GaAs
• Further tests
• Non-ferromagnetic injector
• Structure with different distances from
  injector

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DFG Meeting Halbleiter-Spintronik
Thank You For Your Attention "The most
exciting aspect of this finding is that you
don't know exactly where it's going to lead
D.D.Awschalom
University of Regensburg
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06/07/08 Experiments to probe the inverse
Spin-Hall Effect in GaAs
SPIN-HALL STRUCTURE

S.O. Valenzuela, M. Trinkham, Electrical
detection of spin currents The spincurrent
induced Hall effect, Appl. Phys. 101 (2007)