RAMAKRISHNA MADAKA 09PH6017 Mtech(1ST YEAR)

DEPT.OF PHYSICS&METEOROLOGY I.I.T KHARAGPUR

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INTRODUCTION TO SPINTRONICS MAGNETORESISTANCE ORIGIN OF GMR EXPERIMENTAL SURVEY APPLICATIONS ADVANTAGES & DISADVANTAGES

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Spintronics = Magnetism + Electronics Aim : To find the ways to manipulate the

electron spin in transport process Magnetism and electron spin are interlinked Spintronic devices manipulate spin-polarised

currents by using the electron spin to control current flow

Ferromagnetic materials are appropriate for these devices

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Information is stored into spin as one of two possible orientations

Spin lifetime is relatively long, on the order of nanoseconds

Spin currents can be manipulated Spin devices may combine logic and storage

functionality eliminating the need for separate components

Magnetic storage is nonvolatile Binary spin polarization offers the possibility of

applications as qubits in quantum computers

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GMR

Metal ferromagnetic

{Nonmetal Ferro magnet

,TMR Device, RAM,,,,,,,

Ferromagnetic Materials

(Dilute) Magnetic semiconductors

Spintronics materials

Nonmagnetic semiconductors

{SemiconductorsHetro-Junction

(S-O interaction)

FM/SC hybrid structure

TMR device, Spin-FET,,,,.

{

{

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Rp

Hs

a)

b)

c)

a)change in resistance of the magnetic multilayer as a function of applied field

b)The magnetization configurations of the multilayer at various magnetic fieldsc)The magnetization curve for the multilayer

Rap

FM

FMNM

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Magnetoresistance of three Fe/Cr super lattices at 4.2 K. The current and the applied field are along the same [110]axis in the plane of the layers.

[110]plane

Ref: P.Grunberg, R.Scheriber, Y.Pang,M.B.Brodsky, and H.Soers (1986).” Layered Magnetic Structures: Evidence for ant ferromagnetic Coupling of Fe Layers across Cr Interlayer's” Physical Review Letters 57(19):2242-2445

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60-bilayered Fe-Cr structure at 4.2 K

Nearly 50% drop in resistance observed

Fert :

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Fe-Cr-Fe trilayer at room temperature

1.5% drop in resistance reported

Cont..

Ref .fig:M.Baibich, J. Broto, A. Fret, F.V.Dau,Petroff,P.Etienne, G.Greuzet,A.Freidrich,an J.Chzelas, Phys.Rev.Lett. 61(1988)p.2472.

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Current induced

Current induced

Applied field

Applied fie

ld

Nonlocal layer up-spin conductivity for the case in which the excess spins are aligned on the Co layers

Nonlocal layer down-spin conductivity for the case in which the excess spins are aligned on the Co layers

Fig: 1

Fig:2

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Current induced

Current induced

Applied fie

ld

Applied fie

ld

Conductivity for the case in which excess spins on the Co layers are aligned in opposite directions

Giant magneto conductance is the inverse of giant magneto resistance

Fig:3

Fig:4

Compositional dependence Non magnetic layer thickness dependence Magnetic layer thickness Roughness dependence Impurity dependence Temperature dependence Angular dependence Outer boundary dependence

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GMR in motion sensors is important in our homes, automobiles, and factories.

Film –deposition process Metal detectors Security detectors Memory chips Magnetic-stripe Tag engine control systems Highway traffic monitors

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Advantages : Low power consumption Multipurpose device(amplifiers) No electric current required Faster device Larger storage capacity Smaller device Disadvantages : Controlling the spin for long devices Difficult to inject and measure spin in silicon Silicon causes electrons to loose their spin state

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The discovery of GMR was very rapidly recognized by scientific community.

GMR was good example of how an unexpected fundamental scientific discovery can quickly give rise to new technologies.

This is the opened the door to a new field of science, magneto electronics.

Now magneto electronics is a driving force for new applications of nanotechnology.

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M.Baibich, J. Broto, A. Fret, F.V.Dau,Petroff,P.Etienne, G.Greuzet,A.Freidrich,an J.Chzelas, Phys.Rev.Lett. 61(1988)p.2472.

S.S.P. Parkin, Z.G. Li, and D.J Smith,Appl. Phys.Lett.58 (1991) P. 2710. J.S. Moodera, L.R. Kinder, T.M. Wong, and Rmeservey, Phys. Rev. Litt.74

(1995) P.3273; T. Miyazaki and N. Tezuka, J. Magn. Magn.Mater. 139(1995) p. L21.

L.Berger, Phys. Rev. B.74 (1996) P.9353. J.C. Slonczewski, J. Magn. Magn. Mater. 159(1996)P. L1 .

S.S.P. Parkin, Appl. Phys. Lett. 61 (1992) p. 1358; S.S.P. Parkin, Phys. Rev.Lett.71 (1993) p.1641 .

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The Nobel Prize in Physics 2007“For the discovery of Giant Magnetoresistance“ Albert Fert & Peter Grünberg

Albert Fert Peter Grünberg

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