lateraler Spin-Torque Racetrack

Stromgetriebene Domänenwand-Bewegung

Z. Li and S. Zhang, PRL 93,127204 (2005)

B. Krüger et al., PRB 75, 054421 (2007)

precessional

term

damping

term

( ) ( )( ) ( ) ( )MjMM

bMjMM

M

b)HM(M

M

αγHM

dt

Md

s

j

s

j

eff

S

eff

rrrrrrrrrrrrrrrr

∇⋅×−+

−∇⋅××++

−

××+×

+−= αξ

ααξ

αγ

α 222 1

11

1

1

1

1

motion term distortion term

G. Tatara

sf

ex

τ

τξ = degree of nonadiabaticity)1( 2ξ

µ

+=

S

Bj

eM

Pb Current coupling parameter

current pulse (e-)

a. What is the velocity of domain walls?

Hayashi et al. PRL 98

037204 (2007)

Time resolved resistance measurementwith a digital sampling oscilloscope

110 m/s

Kläui et al. PRL 95

026601 (2005)

SEMPA0.3 m/s

Meier et al. PRL 98

187202 (2007)

Magnetic transmission x-ray microscopy110 m/s

Yamaguchi

et al. PRL 92

077205 (2004)

Magnetic-force microscopy3 m/s

Tatara, KohnoPRL 92

086601 (2004)

theoretical~ 250 m/s

Zhang, Li PRL 93

127204 (2004)

theoretical6-60 m/s

switched area per pulse

Current-induced domain-wallvelocity

Permalloy ring: width 1000 nm, thickness 60 nm

1.2 ns

t

V

Extremely short pulses

Investigation of stochastic domain-wall motion

P(A)~e-τ

PRL 98, 187202 (2007)

Domain-Wall motion

~ 100 m/s

Distortion

(Vortex-Antivortex Generation)

τ ~ 0.9 ± 0.2

e-1 µm

simulation parameters

• ξ = 0.01

• α = 0.01

• j=1.0 x 1012 A/m²

b. Free oscillation of a domain wall in a constriction

Micromagnetic simulation

of the static magnetization

50 µm 20 µm

Soft x-ray image

1 µm

Time resolved observation of

current induced domain-wall motion

L. Bocklage, R. Eiselt, M. Bolte, B. Krüger, P. Fischer, and G. Meier,

“Time-resolved x-ray microscopy of current-induced domain-wall oscillations”, in preparation

Time resolved observation of

current induced domain-wall oscillationDW motion determined from soft x-ray images

FFT of free oscillation

( ) ( ) ( )0

0 cos tteatftt −⋅= −Γ− ω

Initial amplitude : a = 125 nm

• Damping parameter: Γ = 0.554 GHz

• Frequency of free oscillation:

ω = 3.60 GHz

(υ = 573 MHz)

• Time zero: t0 = 1.85 ns

Parameters

Domain-wall velocity

vmax = 325 m/s

1.1 ns

2.2 ns

3.3 ns

Different pulse lengths

Racetrack Memory

S. S. P. Parkin et al., Science 320, 190 (2008)

Racetrack Memory

M. Hayashi et al., Science 320, 209 (2008)