spintronics and its emergence as next generation of
TRANSCRIPT
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APPU JOSEPH XAVIER
S7-A25
Guided by,
Mrs. Asha Murali
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INTRODUCTION.
HISTORY OF SPINTRONICS.
WHY SPINTRONICS IS IMPORTANT.
MAIN CHARACTERISTICS OF SPINTRONICS.
GIANT MAGNETO RESISTIVE.
HOW GMR WORKS.
DATTTA DAS TRANSISTOR.
MRAM.
PLASTIC SPINTRONICS.
PRESENT DAY SPINTRONICS.
ADVANTAGES AND FUTURE OF SPINTRONICS.
DRAWBACKS.
REFERENCES.
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Conventional electronics based on charge.
Have problems like power dissipation and energy loss in
nanoscale devices.
Spintronics based on spin of electrons. Clockwise spin and anticlockwise spin.
Spin controlled electrons used for transfer of info.
Longer relaxation time and easily manipulated.
Provides faster and more efficient devices.
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Started in early 80s with experiments on spin dependant
electrons.
In 1988 Albert Fert and Peter Grnberg discovered GMR.
Giantmagnetoresistance(GMR) brought rise in spintronics.
In 2004:A family of silicon-based semiconductors that exhibit
magnetic properties has been discovered.
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In 2008: came the most significant breakthrough inspintronics.
Scientists discovered methods to inject spin polarised
electrons in semiconductor.
Radically transformed semiconductor spintronics with many
other findings like MRAM , liquid ferromaterials for electron
injection etc.
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Can be easily manipulated by applying
electric field.
Another property is its long coherence orrelaxation time.
It is not easily destroyed by scattering or
collision defects,unlike charge states.
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Metal based spintronics
_This category of spintronicshas been successful inproviding effective information storage.
_eg: Giant Magneto Resistance(GMR).
Semiconductor based spintronics
_Compared to metal based spintronics, semiconductorspintronics is more promising.
_Compatible with existing semiconductor technologies._Contains spin injector , spin transfer and spin detector.
Devices that manipulate the quantum spin states of individualelectrons
_category of spintronics is looking forward toward the moredistant future
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GMR has triggered the rise of a new field ofelectronics called spintronics
used extensively in the read heads of modern harddrives and magnetic sensors.
In 2007 nobel prize was awarded to Albert Fert andPeter Grunburg for the discovery of GMR.
1988 France, GMR discovery is accepted as birth of
spintronics.
A Giant MagnetoResistive device is made of atleast two ferromagnetic layers separated by a
spacer layer
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GMR structures are ferromagnetic alloys sandwichedaround an ultrathin nonmagnetic conducting middlelayer.
When the magnetization of the two
outside layers is anti parallel, high
resistance.
Conversely when magnetization of two outside layers is
parallel, low resistance.
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Applying an external magnetic
field (D)aligns magneticmoments
in alloy (B) layers.
used to construct exquisitely sensitive detectors of
changing magnetic fields such as marking the data
on a computer hard-disk platter.
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One electrode acts as an emitter, the other as collector(similar, in effect, to the source and drain).
The emitter emits electrons with their spins oriented
along the direction of the electrodes magnetizationwhile the collector (with the same electrodemagnetization) acts as a spin filter and accepts electronswith the same spin only.
the gate electrode produces a field that forces the
electron spins to precess.An electron passes through the collector if its spin is
parallel, and does not if it is anti parallel, to themagnetization
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Conventional RAM chip technologies store data as
electric charge or current flows.
In MRAM , typically a0 for aligned state and1for anti -aligned state.
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MRAM uses electron spin to store information.
It requires less power than the conventional
magnetic magnetic storage technologies.
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Epstein and his coauthors reported that by using
magnetic field ,spin polariazation can be made in
plastic. The advent of plastic electronics opens up many
opportunities or new technologies such as
flexible displays and inexpensive solar cells.
Weigh less and less cost.
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Three main steps involved in information transferin semiconductor :
SPIN INJE
CTION,SPINTRANSF
ER,SPINDETECTION
Was possible at low temprature earlier.
Hence needed costly equipments for this purpose.
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But now charges can be transferred at room temprature. Done by introducing a thin layer of oxide betweem the
magnetic material and semiconductor. This in effect creates spin polarised electrons in the
semiconductor.
This breaktrough helps in making energy efficient chips.
Power loss also very low.
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Spintronic devices are smaller, more versatile and more robustthan those currently making up silicon chips and circuit elements.
Make energy efficient chips.
Spintronic RAM chips: increase storage densities by a factor of three have faster switching and rewritability rates.
Since Spins don`t change when power is turned off, the memoryremains non-volatile.
Battery sizes considerably reduced.
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How to efficiently inject spin polarized currents
into a semiconductor;
How to maintain the information stored in spin-
polarized current during the transport andmanipulation;
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MRAM has been introduced and is gradually gaining prominence. A 1.2 petabyte (1200 Terabyte) disk drive based on Spintronics is
almost ready.
A new memory technology based on Spintronics called Racetrack
will soon be available .
Information transfer to a semiconductor at room temprature opens
window for faster chips.
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The spin of the electron has attracted renewed interest because it
promises a wide variety of new devices that combine logic,
storage and sensor applications.
Moreover, these "spintronic" devices might lead to quantum
computers and quantum communication based on electronic
solid-state devices, thus changing the perspective of
information technology in the 21st century.
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Peng Xiong, Department of Physics and MARTECH,Florida State
University Spin Electronics (June 2002).
Spintronics Research Group, University of PlymouthSpintronics The
21st Century Electronics. Lynn Yarris, Berkeley Labs The Current Spin onSpintronics (January
2006).
From hard-disk to healthcare: What canSpintronics do for you? - Summer
Science Exhibition(2008).
Josh Schaefferkoetter, Introduction to Spintronics(February 2007).
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