Spintronics and Its Emergence as Next Generation Of

8/8/2019 Spintronics and Its Emergence as Next Generation Of

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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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Spintronics and Its Emergence as Next Generation Of