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Spin Hall Effect induced by resonant scattering on impurities in metals

Spin Hall Effect induced by resonant scattering on impurities in metals. Peter M Levy New York University In collaboration with Albert Fert Unite Mixte de Physique CNRS, and Universite Paris-Sud. Spin Hall Effect (SHE). Spin current without charge current. Spin current. Intrinsic SHE:

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Spin Hall Effect induced by resonant scattering on impurities in metals

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  1. Spin Hall Effect induced by resonant scattering on impurities inmetals Peter M Levy New York University In collaboration with Albert Fert Unite Mixte de Physique CNRS, and Universite Paris-Sud

  2. Spin Hall Effect (SHE) Spin current without charge current Spin current Intrinsic SHE: due to S-0 effects on the wave functions of the lattice Extrinsic SHE: due to S-0 terms of scattering potentials

  3. Ferromagnetic contact Detection x Injection of spin-polarized current y nonmagnetic contact V 0 w t = thickness S. Zhang, PRL 85, 393 (2000)

  4. How the SHE could be used in spintronic applications: Spintronics need currents that are spin polarized. The conventional method of obtaining a polarized current is to pass an ordinary charge current through a ferromagnetic metal. However, it is difficult to integrate ferromagnetic metals with CMOS [silicon-based] circuits that make up the active memory of computers. Therefore there is great interest in finding nonmagnetic metals or semiconductors which are capable of converting charge to spin currents. As we will see the Spin Hall Effect has this potential; this has lead to the current interest in this effect. The origins of the SHE are the same as those that have produced the Anomalous Hall Effect (AHE) which has been known for over 6-7 decades. The AHE is caused by ordinary charge currents and produces additional contributions to the ordinary Hall effect; it is caused by spin-orbit coupling effects on the band structure, defect scattering, and the expression for the electric current (anomalous velocity or side jump). The SHE is caused by the same mechanisms but relies on the presence of a spin- polarized current.

  5. Previous work on the SHE: The idea of a SHE was first proposed by M. I.Dyakonov and V. I. Perel, Phys. Lett. A 35, 459 (1971). The term Spin Hall Effect was first used by Jorge Hirsch PRL 83, 1834 (1999). Shufeng Zhang made the first realistic calculation of the signal produced by this Effect in metals with finite spin diffusion lengths. PRL 85, 393 (2000). It was further studied by amongst others: J. Sinova, D. Culcer, Q. Niu, N. A. Sinitsyn, T. Jungwirth, A. H. MacDonald, PRL 92, 126603 (2004). Also, see articles by Jairo Sinova in PRB and PRL 2004-2010; and Sinova’s Viewpoint article “Spin Hall effect goes electrical” in Physics 3, 82 (2010).

  6. Introduction: Hall effect due to magnetic impurities in metals RH/R0 1/T Skew scattering

  7. No contribution to the Hall effect Mn impurities in Cu Spin-polarizes the current 1981 The SHE of nonmagnetic Cu alloys could be detected using the spin-polarized current induced by Mn impurities (0.01%) Today The SHE of nonmagnetic conductors can be detected by injecting a spin-polarized current from a ferromagntic contact

  8. Nonmagneticimpurities T with large spin-orbitinduce SHE revealed by the Mn-inducedcurrent spin polarization Mn impurities +fieldpolarize the currentwithoutinducing Hall effect by themselves Cu + y nonmagneticimpurities T + x Mn impurities (y 100-2000 ppm, T=Ir,Lu,Ta, Au) ( x  100 ppm)

  9. RH Vy/H 1/T skew scat. identified by 1/T contrib. to RH scat

  10. R.Asomoza, AF et al, JLCM 1983 Gd + Lu impurities Ni + various impurities Side jump H c  0 Hof skew scatt. A. Fert and O. Jaoul, PRL 28, 303, 1972

  11. SHE induced by resonant scattering on spin-orbit split impurity d levels Partial wave phase shift analysis of resonant scattering (Friedel’s virtual bound state model) Spin-orbit split 5d states of Lu j =5/2 j =3/2 EF Accomodation of one 5d electron(Z5d=1 for Lu)

  12. Skew scattering: scattering probability to the right scattering probability to the left H= xy/xx = constant, xx cI, xy  cI x x y y Ex j Scattering with side-jump: side-jump of the mass center of the scattered electrons H = y/ cI , xy= H xx (cI)2 Re-emission probability to the left = p(1-p) Side-jump y = vt of the center of mass Re-emission to the left at time t+t * Re-emission probability to the right = p * Re-emission to the right at time t Spin up el. H= y/ I  cI Spin up el. x Ey the deflection angle H is characteristic of the scattering asymmetry y H 

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