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Influence of spinon conduction

Magneticnanostructures

Memory (M-RAM)

GMR, TMR, etc

Spintronics

Spin up electron

Spin down electron

Albert Fert, UMR CNRS/Thales, Palaiseau, and Universit Paris-Sud, Orsay, France

Magnetic switching

and microwave

generationbyspin

transfer, spintronics

withsemiconductors,

molecular spintronics,

etc

The origin, the development and the future of

spintronics

spin

charge

lectron


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E

EF

n (E)

n (E)

Spin dependent conduction in ferromagnetic metals(two

current model)Mott, ProcRoy!oc A"#$, "%$&

Fert et al, PR' ", ""%, "%&*

'oegel-+autier, P! $, "%."

Fert et al,PhysF&, */%, "%.&

0orle1in et al, i2id F., $, "%..

I

I = / or= (- )/ (+ )

= (- 1)/(+ 1)

E

EF

n (E)

n (E)

3i d 2andr dlevel

4irtual

2ound

state

0.3

20

r dlevel

3i d 2and

5i 4 r Mn Fe o 3i


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Mixing impriti!s " and # with opposit! or simi$ar spin asymm!tri!s% the

pre-concept of GMR

Example: Ni + impuritiesand!(Fert-Campbell, 1968, 1971)

"st case #d

caseA 6 ", 78 " A and76 "$igh mo%ilit& channel low

A7 66 A9 7 A7A9 7

spin

spin

spin

spin

&. d! 'hysi! 32 1*1

:;


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Molecular Beam Epitaxy(growt of metallic multilayers!


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"e

"e

#r

#r

$Magnetic multilayers

"e


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"e

"e

#r

#r

Magneti%ations of"e layers at %ero fieldin "er multilayers


"e

P. Grnberg, 1986 antiferromagnetic interlayer coupling


7/46

"e

"e

#r

#r

Magneti%ations of

"e layers in anapplied field

in "er multilayers


"e

Read head of

hard disc drive

GMR sensor# nm

Ma"netic #ields

"enerated by the $edia

"%%. (2efore +MR) = " +2it;in,. = +MR heads ? $ +2it;in

,o$tag!

crr!nt


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Arrays of +MR 2iochips for analysis of

2iomolecules ( e@ample= antigens are trapped 2yanti2odies and also decorated 2y other anti2odies

la2elled 2y magnetic nanoparticles which are

detected 2y a +MR sensor)

% m (Philips), "m (!anta 7ar2ara)

Pro2e arrays foranalysis of thousandsof different targets in

parallel


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? " nm

$!agnetic Tunnel "unctions,Tunneling !agnetoresistance#T!$%

Low resistance state High resistance state

ferromagnetic electrodes

tunnelingbarrier

(insulator)"'

'

% d!nsity/sp!!d o"M/"M +

non,o$ati$ty + $ow

!n!rgy consmption

Applications: - read heads of Hard Disc Drive

- M-RAM (Magnetic Random Access Memory)

MRAM

!oodera et al, 199&, !iyasa'i et al,199&,o(e)*l+-)o, !$ -/0

"ulli2re, 193&,

lo4 T, hardly

reproducible

0.1 m


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irst !xamp$!s on !/Mg/!(001)%

4/5ha$!s (#ow!n " !t a$

"'62001) 4ancy (ar!-7inc!nt !t a$

"'6 2003) 5s8ba (9asa !t a$ 4atr!

Mat. 200:) I#M ('ar8in !t a$ 4atr!

Mat. 200:) ;.!tc

Epitaxial magnetic tunnel 'unctions (Mg etc)

uasa et al, Fe;MgB;Fe

4atr! Mat. 200:


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Mathon and Hmers>i, PR 7 "%%%

Mavropoulos et al, PR' 7utler

et al , PR 7 "

Ihang and 7utler, PR 7 / >bcc

o/Mg/bcc o(001)?

P

AP 1

2@

1

:

:2@

Ah d # $ ' # 200B B d M O


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Ahang and #t$!r ' # 200B

P

AP 1

2@

1

:

:

2@

!g, 5ne (Mavropoulos et al, R! "###),etc

1symmetry #sp% slo4ly decaying

tunneling of oma7ority spinelectrons

rTi- and otherd/bonded insulators

($elev et al , R! %&, "##&' oen et al, R

"##*)

&symmetry #d% slo4ly decaying

tunneling ofo minority spinelectrons

in agreement 4ith the negative

polariation of ofound in T!$ 4ith

rTi- ,Ti+and e1/:a+barriers

(de +eresa, A et al, .cience /%%%)

Beyond MgO

Ah d # t$ ' # 200B B d M O


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Ahang and #t$!r ' # 200B

P

AP

!g, 5ne (Mavropoulos et al, R! "###),etc

1symmetry #sp% slo4ly decaying

tunneling of oma7ority spinelectrons

rTi- and otherd/bonded insulators

($elev et al , R! %&, "##&' oen et al, R

"##*)

&symmetry #d% slo4ly decaying

tunneling ofo minority spinelectrons

in agreement 4ith the negative

polariation of ofound in T!$ 4ith

rTi- ,Ti+and e1/:a+barriers

(de +eresa, A et al, .cience /%%%)

Beyond MgO

1

2@

1

:

:2@Physical basis %# & spin

polariation '(P)

;Tunneling


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pin Transfer#magnetic s4itching, micro4ave generation%

pintronics 4ith semiconductors

pintronics 4ith molecules


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>ntroductionP%/G!$

(M%sca, AF et al, MMM ..)

!$ratio#1%

0 nm

6 nm

C%/Cu urrent to Plane #PP% G!$(0Pirau1, AF et al, AP0 .2,MMM .)

>P/G!$

scaling length ? mean free path

PP/G!$scaling length ? spin diffusion

length @@ mean free path

spin accumulation theory,

(3alet-Fert, PR 4 .5)

6 nm

S i i j ti / t ti t NM/FM i t f


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FM

sfl = spin dision $!ngth in M

= spin dision $!ngth in 4MNM

sfl

Spin injection/extraction at a NM/FM interface (beyond ballistic range)

NM FM

zone of spin

accumulation

NM

sfl

FM

sfl

EF

EF=spinchemical potential

Spin accumulation

= EF-EF

Spin current= J-J

EF-EF~ exp(z/ ) in FMFM

sfl

EF-EF~ exp(-z/ ) in NMNM

sfl

NM

sfl

FM

sfl

EF

= spinchemical potential

E

J-J

J+J= current spin polarization

(illustrati%n in the si$+lest

case 6 #lat band, l%7 current,

n% inter#ace resistance,

sin"le +%larity)

(!xamp$!% 0.: m in C10m in carbon

nanotb!)

S i i j ti / t ti t S i d t /FM i t f


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NM= metal orsemiconducto

r

FM

zone of spinaccumulation

NM

sfl

FM

sfl

EF

EFSpin accumulation= EF-EF

Spin current= J-J

NM

sfl

FM

sfl

EF

E

A!? metal

emiconductor) ( metal

>f similar spin spliting on both sidesbut much larger density of states in

( metal

much larger spin accumulation

density

and much more spin flips

on magnetic metal side

almost complete depolariation of

A! ?

semiconductor

1) situation withoutinterface resistance

( conducti!ity "is"atch #)

(Sch"idt et al$ %& ' )

Spin injection/extraction at a Se"iconductor/FM interface

S i i j ti / t ti t S i d t /FM i t f


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NM=semiconducto

r

EF

asbah ' # 2000

".-&arDs ' # 2001

Spin accumulation

= EF-EF

NM

sfl

FM

sfl

EF

Current Spinolarization

(J-J)/(J+J)

FM spin dependent. interf.

resist. #e


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!pin transfer

( !loncews>i, MMM "%%&, ' 7erger, PR 7 "%%&)

!

81C%balt/C%++er/C%balt

! i t f


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!pin transfer

( !loncews>i, MMM "%%&, ' 7erger, PR 7 "%%&)

!

STorCue on !#!!%

81C%balt/C%++er/C%balt

*he transerse component of the

spin current is a%sor%ed and

transferred to the total spin of thela&er

F M x (M x M0)

= periments on pillars


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M!ta$$ic pi$$ar :0x1:0nmG

"

I - 7 -

/ nm" nm

(ree ferro

(ie

d

ferro

u

5nn!$ Fnction

"

I - 7 -

/ nm" nm

(ree ferro

(ied

ferro

barrier

=periments on pillars

a% (irst regime #lo4 D%!%

b% econd regime #high D%

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