Spin does not replace charge current just provide extra control Using suitable materials, many different “bit” states can be interpreted
•Introduction•GMR•Devices•Future Demand•Conclusion•Advantages and Disadvantages•References
Spintronics is a NANO technology which deals with spindependent properties of an electron instead of charge dependentproperties
•Spin is a quantum mechanical property•The rotational moment creates a small magnetic field•The electron spin given a direction up or down•The up and down direction given a of (1) or (0) samething as the electron positive or negative chargecorrespond to those values•Key concept is controlling the spin of electrons
What Is Spintronics ?• In conventional electronics, electron charge is used for manipulation, storage, and transfer of information .• Spintronics uses electron spins in addition to or in place of the electron charge.
Why We Need Spintronics !Failure of Moore’s Law : Moore’s Law states that the number of transistors on a silicon chip will roughly double every eighteen months. But now the transistors & other components have reached nanoscale dimensions and further reducing the size would lead to: 1. Scorching heat making making the circuit inoperable. 2. Also Quantum effects come into play at nanoscale dimensions. So the size of transistors & other components cannot be reduced further.
• 1988 France, GMR discovery is accepted as birth of spintronics• A Giant MagnetoResistive device is made of at least two ferromagnetic layers separated by a spacer layer• When the magnetization of the two outside layers is aligned, lowest resistance• Conversely when magnetization vectors are antiparallel, high R• Small fields can produce big effects• parallel and perpendicular current
Gaint Magnetoresistance (GMR) The basic GMR device consists of a layer of non -magnetic metal between two two magnetic layers. A current consisting of spin-up and spin-down electrons is passed through the layers. Those oriented in the same direction as the electron spins in a magnetic layerpass through quite easily while those oriented in the opposite direction are scattered.
Advantage Spintronics Low power consumption. Less heat dissipation. Spintronic memory is non-volatile. Takes up lesser space on chip, thus more compact. Spin manipulation is faster , so greater read & write speed. Spintronics does not require unique and specialized semiconductors. Common metals such as Fe, Al, Ag , etc. can be used.
1. MRAM (Magnetoresistive Random access)2. Spin Transistor3. Quantum Computer
•MRAM uses magnetic storage elements instead of electric used inconventional RAM•Tunnel junctions are used to read the information stored inMagnetoresistive Random Access Memory, typically a”0” for zeropoint magnetization state and “1” for antiparallel state
MRAM Magneto resistive RAM Array structure ofMRAM•Reading: transistor of theselected bit cell turned ‘on’+ current applied in the bitline• Writing: transistor of theselected bit cell turned ‘off’+ currents applied in the bitand word lines•Need of 2 magnetic fieldsfor writing
•Current passed through a magnetic field becomes spin polarized•Ideal use of MRAM would utilize control of the spin channels ofthe current•Spin transistors would allow control of the spin current in the samemanner that conventional transistors can switch charge currents•Using arrays of these spin transistors, MRAM will combinestorage, detection, logic and communication capabilities on a singlechip•This will remove the distinction between working memory andstorage, combining functionality of many devices into one
•The Datta Das SpinTransistor was first spindevice proposed for metal-oxide geometry, 1989•Emitter and collector areferromagnetic withparallel magnetizations•The gate providesmagnetic field•Current is modulated bythe degree of precession inelectron spin
A Quantumcomputer, incontrast, lies onencodinginformation within tquantum bits orqubits, each ofwhich can exist in asuperposition of ‘0’and ‘1’.
•Moore’s Law states that the number of transistors on asilicon chip will roughly double every eighteen months•By 2008, it is projected that the width of the electrodesin a microprocessor will be 45nm across•As electronic devices become smaller, quantumproperties of the wavelike nature of electrons are nolonger negligible•Spintronic devices offer the possibility of enhancedfunctionality, higher speed, and reduced powerconsumption
Advantages Disadvantages.low power consumption .Controlling the spin for long. Multi purpose devices distances(amplifiers) .Combining techniques.No electric current between therequired semiconductor and magnetic.Faster Devices recording industry.Larger storage capacity .Difficult to inject and.Smaller devices measure spin in silicon .Silicon causes electrons to lose their spin state
This technology will exploit the spin of theelectron and create new devices and circuits whichcould be more beneficial in future by providingdevices like memories for data base accessing withthe speed of light. The devices of this technology are very usefulfor transaction processing and for scientific numbercrunching. Moreover, these "spintronic" devices mightlead to quantum computers and quantumcommunication based on electronic solid-statedevices, thus changing the perspective ofinformation technology in the 21st century