T. Tanaka and H. Kontani- Giant Extrinsic Spin Hall Effect due to Rare-Earth Impurities

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Giant Extrinsic Spin Hall Effect due to Rare-Earth ImpuritiesNagoya University T. Tanaka and H. Kontani

MessagesExtrinsic SHE by focusing on Ce- and Yb- impurities Orbital degrees of freedom is significant to realize giant extrinsic SHE as well as the intrinsic mechanism.

Intrinsic and Extrinsic Mechanisms Intrinsic SHC: Takes a material-specific valueSHCs in various transition metalsTanaka et al.,PRB (2008) 64 cm in Pt

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Agree well with the recent experimental observations by Otani's group.

Extrinsic SHCDue to impurity scatteringSkew scattering term: Side jump term:

In principle, large SHC arises in the low resistivity metals. Study of the extrinsic SHE may be significant for realizing excellent spintronics device.

Motivation for the present studySpin-orbit interaction:

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extrinsic contribution due to l = 0 impurity potential is very small.

In contrast,

cf. Smit: enhancement factor due to multiband effect Not easy ( ~ 104 ) to estimate!

We focus on the orbital degrees of freedom (l = 0) of impuritiesStudy the extrinsic SHE based on a single-impurity Anderson model for Ce and Yb atoms (AHE by Fert et al. PRB,1976)Large SOI and angular momentum

spin Hall angle due to skew scattering term: O(10-1)cf) Spin Hall angle in Pt ~ O(10-3)

Used as a highly efficient way to generate spin current

Model and Hamiltonian 1Anderson Hamiltonian5d 4f

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c-d and c-f mixing potential

Strong atomic SOI for only f-electrons.(14-fold degeneracy) L=3,S=1/2 JJ=7/2 =7/2(8-fold degeneracy) 3+ 13

C-G coefficient

Yb (f )

~3000K

SOI

SOI