C u r r e n t - i n d u c e d ma g n e t i z a - - PowerPoint PPT Presentation

1

C u r r e n t

• i

n d u c e d ma g n e t i z a t i

• n

d y n a mi c s i n n a n

• ma

g n e t

T e r u

• O

n

• I

n s t i t u t e f

• r

C h e mi c a l R e s e a r c h , K y

• t
• U

n i v e r s i t y

N a n

• ma

g n e t s : Wi r e & D i s k

Domain wall in nanowire Magnetic vortex in disk

2

I n s t i t u t e f

• r

C h e mi c a l R e s e a r c h D i v i s i

• n
• f

Ma t e r i a l s C h e mi s t r y N a n

• s

p i n t r

• n

i c sL a b .

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• P. Fischer (LBNL)

A.Thiaville (Paris-sud.)

• H. Kohno (Osaka)
• Y. Nakatani (UEC)

A c k n

• wl

e d g me n t s

• G. Tatara (Metropolitan)

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Magnetics to Spintronics

Data writing : changing the magnetization direction Conventional : magnetic field produced by current flow (discovered by Ørsted in 1820) Not efficient: field spread out, non-local method

• e

N S

Use of coupling between charge and spin!

Local and efficient writing

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Current-driven domain wall motion

(Action-reaction law)

Spin rotates anti-clockwise. Local magnetic moment should rotates clockwise.

DW motion by electric current without magnetic field!!

Static domain wall D

• m

a i n w a l l C u r r e n t Action-reaction!

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Sample for a single DW injection

Ni81Fe19(10nm)

H

DW inj ect or

• K. Shiget o et al.,Appl. Phys. Let t . 75 (1999) 2815.

240 nm

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MFM observation of current-driven domain wall motion (head-to-head domain wall)

7 ×1

1 1 A

/ m

2

, 5 µs 7 ×1

1 1 A

/ m

2

, 5 µs

D W m

• v

e s

• p

p

• s

i t e t

• c

u r r e n t d i r e c t i

• n

, d i r e c t i

• n
• f

e l e c t r

• n

f l

• w

.

Current (7×1011 A/m2, 5µs) Current (7×1011 A/m2, 5µs)

+

• H

Ni81Fe19 wire widt h: 240 nm t hickness: 10 nm

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Current-driven domain wall motion (tail-to-tail domain wall)

+

• H

T a i l

• t
• t

a i l D W a l s

• m
• v

e s

• p

p

• s

i t e t

• c

u r r e n t d i r e c t i

• n

.

7 ×1

1 1 A

/ m

2

, 5 µs 7 ×1

1 1 A

/ m

2

, 5 µs

Current (7×1011 A/m2, 5µs) Current (7×1011 A/m2, 5µs)

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Successive images of DW motion by current pulse injections

(7×1011 A/m2, 0.5 µs)

D W p

• s

i t i

• n

c a n b e c

• n

t r

• l

l e d b y c u r r e n t p u l s e d .

• Phys. Rev. Let t ., 92 (2004) 077205.

NiFe, w = 240nm, t = 10nm

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Field-driven v.s. Current-driven DW motion

Ma g n e t i c f i e l d

• d

r i v e n D W mo t i

• n

D W s a n n i h i l a t e e a c h

• t

h e r …. E l e c t r i c c u r r e n t

• d

r i v e n D W mo t i

• n

D W s a r e m

• v

i n g t

• g

e t h e r t

• t

h e s a m e d i r e c t i

• n

. I n f

• r

m a t i

• n

( D W ) c a n b e t r a n s f e r r e d !

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Magnetic Racetrack Memory proposed by IBM

A n

• v

e l t h r e e

• d

i me n s i

• n

a l s p i n t r

• n

i c s t

• r

a g e me mo r y Magnetic nanowires: information stored in the domain

• Capacity of a hard disk drive
• Reliability and performance of solid state memory

(DRAM, FLASH, SRAM...) Courtesy of Stuart Parkin (IBM)

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T M R 素子 BL BL WL GND

セル構成図（ 例）

書込み電流 読出し電流 BL BL WL GND BL BL WL BL BL WL GND

セル構成図（ 例）

書込み電流 読出し電流 書込み電流 読出し電流 T M R 素子

Activities of DW devices in Japan NEC Fujitsu

Fast MRAM Storage

NEDO Spintronics nonvolatile devices project

Replace SRAM Post HDD

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T . S h i n j

• e

t a l . , S c i e n c e , 2 8 9 ( 2 ) 9 3 .

M F M , M F M , N

i F e N i F ed i s k d i s k

C u r l i n g s p i n s t r u c t u r e t

• r

e d u c e t h e m a g n e t

• s

t a t i c e n e r g y . H

• w

e v e r , a t t h e c e n t e r

• f

t h e d i s k , t h e e x c h a n g e e n e r g y i n c r e a s e s w i t h d e c r e a s i n g t h e a n g l e b e t w e e n n e i g h b

• r

i n g s p i n s . V

• r

t e x c

• r

e w i t h m a g n e t i z a t i

• n

p e r p e n d i c u l a r t

• d

i s k p l a n e ! M a g n e t

• s

t a t i c e n e r g y v . s . E x c h a n g e e n e r g y

mz ~ exp[-(r/ ξ)2] , ξ = (2µ0A/ Ms

2)1/ 2 ～5nm

“1” “0”

V

• r

t e x c

• r

e m e m

• r

y

H

• w t
• wr

i t e a n d r e a d ?

What is magnetic vortex?

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Radius of steady orbital (nm)

t = 40 nm Ni80Fe20 Iexc= 3 ×1011 A/m2 (P=0.7)

Resonance of vortex core by AC current

• Micromagnetic simulation including spin transfer term-

, x u ∂ ∂ − × + × − = m m m H m m & & α γ

s B

eM JP g u 2 µ =

Experimental proof: Resistance measurements, Kasai et al., PRL 97, 107204 (2006). X-ray microscope, Kasai et al., PRL101, 237203 (2008).

D= 500nm, t=40nm

Iex

Iex=3 ×1011 A/m2

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Vortex core motion by AC current

with high current density

Iex

Iex = 4×1011 A/m2 D=500nm, t=40nm

V

• r

t e x c

• r

e s w i t c h i n g b y c u r r e n t !

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Observation of Current-induced core switching

Iexc

（ ２ ） （ ３ ） （ 1 ） C h e c k c

• r

e d i r e c t i

• n

（ 2 ） E x c i t a t i

• n

（ 3 . 5 ×1

1 1

A / m

2

, 2 9 M H z ） （ 3 ） C h e c k c

• r

e d i r e c t i

• n

（ 4 ） C

• n

t i n u e t h i s p r

• c

e s s

mA c u r r e n t c a n s wi t c h t h e c

• r

e !

（ １ ） Yamada et al., Nature Materials 6, (2007) 270.

s wi t c h i n g b y s t a t i c f i e l d ～ s e v e r a l k O e

C

• r

e s e e ms t

• s

wi t c h r a n d

• ml

y ? !

17

P r

• b

l e m s

• f

V C s w i t c h i n g b y r e s

• n

a n c e

( 1 ) L

• n

g s w i t c h i n g t i m e

• f

s e v e r a l t e n s n s ( 2 ) P

• r

c

• n

t r

• l

l a b i l i t y

• f

V C d i r e c t i

• n

C r i t i c a l c

• r

e v e l

• c

i t y f

• r

s w i t c h i n g

C r i t i c a l v e l

• c

i t y

S a m e c r i t i c a l v e l

• c

i t y r e g a r d l e s s

• f

t h e c u r r e n t d e n s i t y . C

• r

e v e l

• c

i t y ( n

• t

c u r r e n t d e n s i t y ) i s e s s e n t i a l !

C u r r e n t p u l s e w i t h h i g h e r c u r r e n t d e n s i t y !

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Core switching by current pulse

1.3×1012 A/m, 2.5 ns N i F e d i s k , D = 1 5 5 n m , t = 5 5 n m

・ O n e s h

• t

s w i t c h i n g b y n s c u r r e n t p u l s e ! ・ P r e c i s e c

• n

t r

• l
• f

v

• r

t e x c

• r

e d i r e c t i

• n

!

• K. Yamada et al.,

Appl.Phys.Lett., 93, 152502 (2008).

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M T J f i l m & s a m p l e s t r u c t u r e

Ru(2) PtMn(15) CoFe(1.5) CoFeB(1.0) MgO(1.4) CoFeB(2) Permalloy(20) Si/SiO2 CoFe(2.5) Ru(2) Pinned-layer Free-layer Ta(5)

Pillar size 18x9 µm2

91 . = ∆ R R

MR curve Synthesized by NEC SEM image of the sample 3-terminal devise

V

i n

V

• u

t

20

V

• r

t e x t r a n s i s t

• r

w i t h M T J

input

• utput

Output signal is obtained for resonance frequency. The signal is tuned by bias-voltage to MTJ.

• S. Kasai et al., Appl. Phys. Express 1(2008) 091302.

V

i n

V

• u

t

21 D W v e l

• c

i t y , S c i e n c e ( 1 9 9 9 ) C u r r e n t

• d

r i v e n D W mo t i

• n

, P h y s . R e v . L e t t . ( 2 4 ) V

• r

t e x c

• r

e , S c i e n c e ( 2 ) C u r r e n t

• i

n d u c e d d y n a mc s P h y s . R e v . L e t t . ( 2 6 ) C

• r

e r e v e r s a l b y c u r r e n t , N a t u r eMa t e r i a l s ( 2 7 )

D

• ma

i n wa l l V

• r

t e x c

• r

e

Summary

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T h a n k y

• u

!