Adhnan K.P Hijas H

agreementkittensSemiconductor

Nov 2, 2013 (3 years and 8 months ago)

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Presented by:


Adhnan

K.P


Hijas

H





Also known as magneto electronics


Exploit intrinsic spin of electron and associated
magnetic moment


The researches are started after the discovery of
Gaint

Magneto Resistance (GMR) by Albert
Fert

& Peter
Grunberg

(1998)


Used in number of electronic applications




Spin shows the quantum nature of electrons


Use of
nano

technology


Electrons are spin
-
1/2 fermions


Have two possible state “spin up” & “spin down”


Magnetic field is different for “up” & “down”


Information is carried by the intrinsic spin of electron


Basics was GMR




Big commercial application of
nano

technology


Simplest way to generate spin polarized current in a
metal


Consist of two layer ferromagnetic materials
separated by a space layer


First discovered in Fe/Cr/Fe
trilayers






Magnetization vectors are aligned


resistance is low


Anti aligned
-
resistance is high


Fig:(a)

Fig:(b)


Two variants of GMR

1)

Current in plane (CIP)

2)

Current perpendicular to plane (CPP)


TMR
-
CPP is achieved using quantum mechanical
tunneling






Used in hard disk


Use difference in resistance of parallel & anti
parallel alignment


High GMR is preferred for optimal storage density


CPP has high GMR


Motorola has developed 256 kb MRAM
-
read write
cycle 50ns



Triggers the emergence of
Spintronics


Used in magneto coupler


Vibration measurement in MEMS system



Comprises of



Spin injector



Spin detector


Manipulation of electron spin during transport can be
accomplished using external magnetic field


Information is stored into spins as a particular spin
orientation


Spin is attached to mobile electrons
-
carry information




Information is read at a terminal


Spin orientation of conduction electrons requires
nano

seconds


Used in



Memory storage



magnetic sensors



quantum computing (
qubit

)


Combines the potentials of semiconductor &
magnetic material


Two approaches

1)

Existing

GMR
-

based

technology


2)

Finding

novel

ways

of
both

generation

and


utilization

of spin
-
polarized

currents
.







Uses ferromagnetic semiconductor sources


Manganese doped gallium arsenide (
GaMnAs
)


Magnetized in the same way as iron


Spin detection


Faraday/Kerr rotation of transmitted/reflected
photons



Circular polarization analysis of
electroluminescence



Nonlocal spin valve



Ballistic spin filtering




Provide amplification, general as multifunctional
device

1)
Associating ferromagnetic metals with non
-
magnetic
semiconductor


Have the problems of conductivity mismatch

2)
Fabrication of ferromagnetic semiconductor


Ga
1
-
x
Mn
x
As

3)
Exploiting spin polarized currents induced by spin
orbit effect


Spin Hall Effect (SHE)


Researches are now active


SHE found also in non magnetic metals



Based on spin transport in semiconductors


Conduction is between spin polarized source & drain
with control of spin transmission by field effect gate


They have advantages over MOSFET


A recent emerging direction of
spintronics


Spin transport in carbon
nanotubes


Difference between resistance of parallel & anti
parallel configuration can exceeds 60%
-
70%.


High GMR


On 4.2k
nanotube

(electrode La
2/3
Sr
1/3
MnO
3
)

La2/3Sr1/3MnO3

(LSMO)

La2/3Sr1/3MnO3

(LSMO)

CNT


Used in high speed memory (hard drive up to 1PB)


Miniaturization



1 TB on a single sided 3.5" diameter disc


Excellent data processing speed


Lower electric consumption


Ability to carry out new quantum computation


MRAM


Non
-
volatile memory


Low cost & high speed


Infinite endurance


Creation of
memristor


Melding
memristors

and
spintronics

yields devices whose
resistance changes according to the spin of electron


High speed & high density



Combined use of
nanowire

&
spintronics

revolutionize the
computer memory (
Parkin

2007)


placing
nanowires

vertically from a silicon wafers and
these magnetic
nanowires

serve as the storage medium for
the data.


The data itself is encoded by the use of
spintronics


This technology is million times faster & require less
energy



MEDICAL FIELD APPLICATION


Cancer cell detection


Detect the cancer cells even when they are small in
number


Polarimeter

is used to detect the spin


Mott
polarimeter


MAGNETIC SENSORS & READING
HEADS


GMR is thin layer


high resistance


Small size & low power


Fabricated on a chip


Detect very small magnetic field with very high spatial
resolution



FIELD EFFECT TRANSISTOR


Small in size


Quantum tunneling


Advantages over MOSFET


QUANTUM COMPUTERS


Electron spin represent a bit of information (
qubit
)


Quantum computations