Hiroyuki Inoue

Electric manipulation of spin relaxation in a film using spin-Hall effect K. Ando et al (PRL in press)

Why Spintronics? A Relativistic View

Relativity says Duality of Electricity and Magnetism

BvE

cvE

21

1

E

c

vB

cvB

221

1

PvM

cvM

021

1

MvP

cvP

021

1

E ↔ B

P ↔ M

PvM

cvM

021

1

MvP

cvP

021

1

00, vMP

0, 0 vPvMPP

P

P’

M’v

00, vPM

0, 0 vMvPMM

M

P’

M’

v

PvM

cvM

021

1

MvP

cvP

021

1

N

S

PV

v (jc)

Ｍ

Wilson’s experiment (1913)

rotating magnetization

Inducing electromotiveforce (EMF) (electric polarization P)

electricity → electric charge ρe

electric current → charge current Jc

magnetism → magnetic charge (dipole) ρm

magnetic dipole current → spin current Js

Harness the duality of Electricity and MagnetismE, P

chargeB, Mspin

Fundamental Purposes of Spintronics

Introduction of Spin Current opensa New Perspective to Magnetic Phenomena

A Wise Saying (!?) by Yehoshua

Ah? What is spin current? Why do we need to think about spin current?OK, then, I will go to a market. and I will buy a banana current!

Spin current is not that stupid thing to think about…

x x

μ↑μ↓J↑ J↓

Current of Electrons in Solids

up-spin current down-spin current

Electric Current & Spin Current

=

=

charge spinJc = J↑ + J↓

Js = J↑ - J↓

Charge Current

Spin Current

e

σ

v

v

charge current and spin current

Heff

M

-M×H

D

eff

dM dMM H M

dt M dt

Magnetization damping term

Dissipation of angular momentum

Transferred to conduction electrons

Generation of spin current (μ↑ ≠ μ↓)

Magnetization Relaxation = Production of Spin Current

Phenomenological Description of Magnetization Dynamics

Landau-Lifshitz-Gilbert equation

Heff

M -M×Heff

DBalance of emission and absorption

of angular momentum

Ferromagnetic Resonance

Ferromagnetic Resonance = Continuous Generation of Spin Current

EM2 efff H

Supply angular momentum by EMW

Continuous operation of spin pumping

Maintain magnetization-precession

Driving Magnetization Precession Generates Spin Current

σv

Experiments

-e -e

-eJS

Jc Jc

JS

Spin-Hall effect Inverse spin-Hall effect

1. Zhang et al. PRL (2000)2. Murakami et al. science (2003)3. Sinova et al. PRL (2004)

4. Kimura et al. JMMM (2004)5. Kato et al. science (2004)6. Wunderlich et al. PRL (2005)7. Ueda et al. APL(2006)

intrinsic: Band Berry Phaseextrinsic: Impurity Scattering

Spin Hall Effect

Spin-Orbit interaction (relativistic effect)

Ni81 Fe19 (10 nm)(FM)Pt (10 nm)(NM)

SiO2 substrate EMW

TE011 microwave cavity

H

V,I

Sweep&

Lock-in

HMW

derivative of Lorentzian function

Experimental Setup

0

3

2W

eff

dM dMM H M

dt M dt

μ↑

μ↓

J↑

J↓

Ni81Fe19 Pt

Enhancement of M relaxation

Pt layer Enhances Relaxation of Magnetization

10-3 V/T

EMF due to ISHE ( Js → Jc ) = ( M → P ) Lorentz transformation in a solid

H. Inoue, K. Ando et al. (J. Appl. Phys)

Spin Current Injection Indeed Yields EMF

-e

-e

Jc

JS

Inverse Process Realizes Electrical Manipulation of M-relaxation

I

Spin-Hall effect:spin current injection

to Ni81Fe19 layer

spin torque manipulates the damping term

eff

dM dMM H M

dt M dt

dt

MdM

MHMdivJ

dt

MdeffS

SdivJ

dt

Md δM⊥

M

D

spin torque

spin torque

( Jc → Js ) = ( P → M )

direction of current: direction of polarization of spin current current intensity: amount of spin torque

modulation of M-relaxation asscociated with the current-directional reversal

SHE SS F

JM V

0

3

2W

electrical manipulation of magnetization relaxation

this scheme is applicable for spin-current meter

conventionally, difficult to achieve after once material species, temperature, and pressure are given

They realized electric manipulation of magnetization relaxation, which can be also applied to spin-current meter.

Spin current introduces new perspectives to magnetic phenomena which harness the duality of electricity and magnetism.

Main Points to Remember

magnetic monopoles can exist in solids…

S

N

S

θ θ’

jsi≈∂iθ jssi≈M×∂iM

superconductor ferromagnet

M M’

Super charge current Super spin current

Josephson Effect of Charge and Spin

( ) ( ) eff

dm r m r H

dt

2

i jij

E JS m m

2 2 ( )eff j jj j

H JS m JS m rE

am

22

2

( ) 1 ( )( ) ( )

2

m r m rm r a m r a a

r r

22 2 2 2 2 2

2

( )( ) ( )

m rJS a JS a m r A m r

r

2( ) ( ) ( )dm r A m r m r

dt

A

Deduction of Super Spin Current

2( ) ( ) ( )dm r A m r m r

dt

( ) div cdq r j

dt

( ) div( ( ) ( ))dm r A m r m r

dt

( ) v di sSS

dm r

dtj

2 ( )A A A A

( ) ( )sSSj A m r m r

Charge density

Super Spin Current

Spin Continuity Equation

Electric current

Charge Continuity Equation

Deduction of Super Spin Current