1 / 27

POTENTIAL APPLICATIONS OF SPINTRONICS

POTENTIAL APPLICATIONS OF SPINTRONICS. M.Cahay. Dept. of ECECS, Univ.of Cincinnati, Cincinnati, Ohio 45221 http://www.ececs.uc.edu/~mcahay. February 4, 2005. Outline. A Little quBit of History Success Story: Giant Magnetoresistance Spin Valve

Leo
Download Presentation

POTENTIAL APPLICATIONS OF SPINTRONICS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. POTENTIAL APPLICATIONS OF SPINTRONICS M.Cahay Dept. of ECECS, Univ.of Cincinnati, Cincinnati, Ohio 45221 http://www.ececs.uc.edu/~mcahay February 4, 2005

  2. Outline A Little quBit of History Success Story: Giant Magnetoresistance Spin Valve Requirements for spintronics Zeeman, Spin-Orbit Effects Injection, Manipulation, Detection Magnetoresistive biosensors Conclusions

  3. Brief HistorySpintronics-Magnetoelectronics • Stern-Gerlach Experiment (Early 1920s) • spin concept – 1920s • Pauli-Dirac Equation (Late 1920s) • 1980s… : Study of Mesoscopic systems – Landauer-Buttiker Formalism • Breakdown of Moore’s Law? • 1988: Giant Magnetoresistance in Magnetic multilayers, magnetic read heads, magnetic sensors, spin valves.

  4. Brief HistorySpintronics-Magnetoelectronics • 1990: SPINFET proposal by Datta and Das • 1990s: Lots of work on Ferromagnet/ (metal, semiconductor, superconductor) interfaces. • DMS – diluted magnetic semiconductors (ZnMnSe, GaMnAs,GaMnN,…) • 1985: David Deutsch: Quantum Mechanical Turing Machine

  5. Brief HistorySpintronics-Magnetoelectronics • 1995: P.Schor’s algorithm for fast factorization of large integers (cryptography) • 1997: L.K.Grover’s search algorithm for efficient search of large database • 1990s: Lots of proposal for implementation of qubits and quantum computers (NMR, Ion trap, quantum dot) • Search in Spintronics and Quantum Computing will continue to feed on each other

  6. SIAROADMAP - Moore’s Law

  7. Requirements for Spintronic Integrated Circuits • Simple device structure for high degree of integration and high process yield. • Large magnetocurrent for high speed operation • High transconductance for high speed operation • High amplification capability (V, I, and/or power) • Small power delay product and small off-current for low power dissipation

  8. Preliminaries: Stoner Model E(k) Exchange Energy k Ferromagnetic Contact

  9. GMR Read Head

  10. RAM with GMR Elements

  11. Preliminiaries: Zeeman Effect

  12. Preliminaries:Spin-Orbit Interaction

  13. Ferromagnet/Sm Interface

  14. Contact Selection • Ferromagnetic contact (Fe, Ni, Co) • HMF candidates: Heusler Materials • Dilute Magnetic Semiconductors (GaMnAs, ZnMnSe, ZnMnTe,GaMnN…) • More recently, wide band gap ferromagnetic semiconductors and oxides S.J. Pearson et al., “Wide band gap ferromagnetic Semiconductors and oxides”, Journal of Applied Physics, Vol.93, pp.1-13 (2003)

  15. Ferromagnetic contact/semiconductor interfacesHow good are they? Why Ferromagnetic Contacts (Fe, Ni, Co)? • Because Curie Temperature Is Above Room Temperature! Hence, devices could work at 300k. • FM are good source of spin polarized electron sources (Stoner model) Theoretical Predictions • Classical diffusion eq. predicts very small spin injection efficiency across Fe/Sm interface (G. Schmidt et al. PRB 62,R4790 (2000). Main reason: Large conductivity mismatch between the two materials. • Not so fast! E.I.Rashba (Phys.Rev.B 62 R16267 (2000)). “If you can adjust interface resistance by using a tunneling barrier, the situation can improved drastically!”.

  16. Ferromagnetic contact/semiconductor interfacesHow good are they? Rashba's prediction was confirmed experimentally using (a) Schottky barriers H.J.Zhu et al., PRL 87, 016601 (2001) (Fe/GaAs), 2% efficiency A.T.Hanbicki et al, APL 80, 1240 (2002) A.T.Hanbicki et al, APL 82, 4092 (2003), (Fe/AlGaAs), 33% efficiency (b) Thin Metal Oxides V.F. Motsynyi et al, APL 81, 265 (2002) T. Manago and H. Akinaga, APL 81, 694 (2002) (c) AlAs barriers S.H.Chun et al, PRB 66, R100408 (2002).

  17. Spin Relaxation Mechanisms The Elliot-Yafet Scattering Mechanism As a result of the SO-contribution to the crystal Hamiltonian, conduction-band states of some semiconductors are not spin eigenstates. This leads to the possibility for spin-flip scattering even for spin independent impurity scattering (due to Coulombic scattering for instance). For the same reason, spin-independent electron-electron scattering can also cause spin-flip transitions

  18. DYAKONOV-PERELSPIN RELAXATION IN A QUANTUM WIRE DRESSELHAUS HAMILTONIAN RASHBA HAMILTONIAN x z x y

  19. RAMSAUER (FABRY-PERROT) RESONANCES

  20. ONE REPULSIVE IMP. 300 angs from left contact INFLUENCE OF SCATTERING STRENGTH

  21. Magnetoresistive-Based BiosensorsD.L.Graham et al, Trends in biotechnology vol.22, 455 (2004)

  22. Conclusions Spintronics has already some success stories! (giant magnetoresistance/spin valve) Quantum Computing: Too early to tell! Other potential: Spintronics & organics, Spintronics & Biosensors, Magnetic Sensors. Want to know more about it? Buy the book: “Introduction to Spintronics”….in 2006.

More Related