Fert Slides
Transcript of Fert Slides
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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
$Magnetic multilayers
"e
P. Grnberg, 1986 antiferromagnetic interlayer coupling
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"e
"e
#r
#r
Magneti%ations of
"e layers in anapplied field
in "er multilayers
$Magnetic 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%