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Spin depend electron transport: AMR, GMR. Lecture 2. Magnetorezystancja. Anizotropowa Magnetorezystancja AMR origin spin – orbit coupling (  1960) Gigantyczna Magnetorezystancja GMR 1986 – oscillatory interlayer exchange coupling in Fe/Cr/Fe multilayers

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Magnetorezystancja
Magnetorezystancja

Anizotropowa Magnetorezystancja AMR

origin spin – orbit coupling (1960)

Gigantyczna Magnetorezystancja GMR

1986 – oscillatory interlayer exchange coupling in Fe/Cr/Fe multilayers

P. Grünberg et al. Phys Rev.Lett. 57 (1986), 2442

1988 – GMR in Fe/Cr/Fe multilayers

M. N. Baibich,..., A.Fert,.. et.al. Phys Rev.Lett. 61 (1988), 2472



Galvanomagnetic effects in the plane of thin film

  • Longitudinal magnetoresistivity effect

  • Transversal magnetoresistivity effect



Magnetic field dependence of the longitudinal magnetoresistivity effect (AMR)

if i || Hq =f


G iant m agnetoresistivity gmr

I magnetoresistivity effect (AMR) = const

Ua

magnetoresistance

-

-

U

U

R

R

D

R

a

p

a

p

=

=

»

%

5

100

U

R

R

p

p

p

Giant Magnetoresistivity - GMR

I = const

 10 nm

Up

ferromagnet

nonferromagnet (Cu)

ferromagnet


Thickness dependence of spacer layer
Thickness dependence of spacer layer magnetoresistivity effect (AMR)


GMR is isotropic in respect to the current magnetoresistivity effect (AMR)


Below, structure of magnetoresistivity effect (AMR)Fe film/ Cr wedge/ Fe whisker illustrating the

Cr thickness dependence of Fe-Fe exchange. Above, SEMPA

image of domain pattern generated from top Fe film. (J. Unguris et

al., PRL 67(1991)140.)


Spin depend conductivity

M magnetoresistivity effect (AMR)

M

I

R small

Spin depend conductivity

I

R large


Density of states in 3 d metals
Density of states in 3-d metals magnetoresistivity effect (AMR)

GMR  due scattering into the empty quantum states above the Fermi level D(EF)

For ferromagnetic 3d metals D(EF)  D(EF)    


Spin polarization of ferrmagnets

Energ magnetoresistivity effect (AMR)y

Energy

Energia

EF

d

d

d

s

s

s

Spin

Spin polarization of ferrmagnets

Magnetization

Density of states


Pseudo spin valve psv m h r h
Pseudo spin valve (PSV) M(H) & R(H) magnetoresistivity effect (AMR)

Two stages charactristics


Magnetic dots
Magnetic dots magnetoresistivity effect (AMR)

Co (4nm)

Cu (3nm)

NiFe (6nm)


M agnetic r andom a ccess m emory mram

0 magnetoresistivity effect (AMR)

1

Magnetic Random Access Memory (MRAM)

ścieżka przewodząca

antyferromagnetyk

ferromagnetyki

nieferromagnetyczna

międzywarstwa

 150 nm


Zastosowania pseudo zawor w spinowych
Zastosowania pseudo-zaworów spinowych magnetoresistivity effect (AMR)

  • Nieulotne pamięci magnetyczne o dostępie swobodnym (Magnetic Random Access Memory)

    • matryca złożona z komórek pamięciowych: elementów PSV

    • bit informacji reprezentowany poprzez wzajemną orientację wektorów namagnesowania warstw ferromagnetycznych twardej i miękkiej;

    • zapis poprzez przemagnesowanie silniejszym prądem;

    • odczyt poprzez detekcję zmiany rezystancji

    • informacja przechowywana jest po zaniku zasilania;

    • szybki zapis i odczyt, mały pobór mocy;

    • cykle zapisujące są nieniszczące;

    • odporność na promieniowanie jonizujące.


Spin valve sv

M(H) magnetization magnetoresistivity effect (AMR)

Spin-Valve (SV)

R(H) magnetoresistance


Spin valve sv m h r h
Spin valve (SV) – M(H) & R(H) magnetoresistivity effect (AMR)

high magnetoresistance field sensitivity


Different gmr structures
Different GMR Structures magnetoresistivity effect (AMR)


  • Conclusions magnetoresistivity effect (AMR)

  • GMR can only be observedif at latest two ferromagnetic layers are separated by non-magnetic metal layers

  • GMR has a maximum, if the magnetization vectors in adjacent

  • F-layers is antiparallel

  • CPP has a larger effect than CIP

  • GMR is a direct image of the magnetic hysteresis

  • GMR is much larger than AMR

  • GMR increases with decreasing temperature

  • GMR depends on the number of F/M interfaces

  • For the GMR effect it is not important how the antiparallel orientation of the magnetization vectors in adjacent ferromagnetic layers is achivied (exchange bias F/AF or exchange coupling SAF)


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