Spin depend electron transport amr gmr
This presentation is the property of its rightful owner.
Sponsored Links
1 / 31

Spin depend electron transport: AMR, GMR PowerPoint PPT Presentation


  • 81 Views
  • Uploaded on
  • Presentation posted in: General

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

Download Presentation

Spin depend electron transport: AMR, GMR

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


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

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


  • Ohms law for galvanomagnetic effects

    m = M / |M|

    mx= sinq cosf

    my= sinq sinf

    mz= cosf,

  • magnetoresistivityDr = r- r


Galvanomagnetic effects in the plane of thin film

  • Longitudinal magnetoresistivity effect

  • Transversal magnetoresistivity effect


  • Angle dependence of the longitudinal magnetoresistivity

    U = R i

    U = Ri


Magnetic field dependence of the longitudinal magnetoresistivity effect (AMR)

if i || Hq =f


I = 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


GMR is isotropic in respect to the current


Below, structure of 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.)


M

M

I

R small

Spin depend conductivity

I

R large


Density of states in 3-d metals

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

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


Energy

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)

Two stages charactristics


Magnetic dots

Co (4nm)

Cu (3nm)

NiFe (6nm)


0

1

Magnetic Random Access Memory (MRAM)

ścieżka przewodząca

antyferromagnetyk

ferromagnetyki

nieferromagnetyczna

międzywarstwa

 150 nm


Zastosowania pseudo-zaworów spinowych

  • 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.


M(H) magnetization

Spin-Valve (SV)

R(H) magnetoresistance


Spin valve (SV) – M(H) & R(H)

high magnetoresistance field sensitivity


Different GMR Structures


  • Conclusions

  • 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)


  • Login