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Introduction to Spintronics Presented by: Ch Ravikumar
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Introduction to Spintronics by Ch.Ravikumar

May 22, 2015

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Technology

The presentation introduces to the new technology competing the The Electronics industry.
It also includes various methods to implement Spintronics.
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  • 1. Introduction to SpintronicsPresented by:Ch Ravikumar

2. Contents 0 Introduction Future demands Spintronics Device working Electronics Vs Spintronics GMR and TMR MRAM Datta das Transistor Advantages Conclusion 3. Introduction 1 Conventional electronic devicesignore the spin property and relystrictly on the transport of theelectrical charge of electrons. Adding the spin degree of freedomprovides new effects, newcapabilities and new functionalities. 4. Future Demands 2 Moores law states that the number of transistors on asilicon chip will roughly double every eighteen months 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 5. VIDEO 6. What is Spintronics? Spintronics is an emerging technology that exploits boththe intrinsic spin of the electron and its associatedmagnetic moment. It is based on the spin of the electron which exists in oneof the two states, namely spin up and spin down, withspins either positive half or negative half. This type of spin creates a tiny magnetic field. The two possible spin states naturally represent 0 and1.This bit of information is called qubit.3 7. Spintronics devices workingAll spintronic devices act according to the simple scheme:1. Information is stored(written)into spins as a particularspin orientation(up or down).2. The spins being attached to mobile electrons, carry theinformation along a wire.3. The information is read at a terminal.4 8. Electronics Vs SpintronicsElectronics SpintronicsPower failure problem No power failure problemBoot up waiting problem inElectronic SystemsNo Boot up waiting problemMore Power Consumption Less Power ConsumptionLess Compact More CompactNormal Speed Faster TransferCheaper Costlier6 9. Effects of SpintronicsThe two important effects based on spintronics are:i. Giant Magneto Resistance (GMR) effectii. Tunnel Magneto Resistance (TMR) effect7 10. GMR effect8 The discovery of GMR in 1988 is considered to be the birthof Spintronics. In 1988, Alberts Ferts group discovered GMR effect It is observed that when multi layers of alternatemagnetic/non-magnetic materials carrying electric currentwere placed in magnetic field, they exhibit large change inelectric resistance, which is also known as magnetoresitance 11. GMR effect The GMR effect caused because the spin-aligned currentsfrom one layer are scattered strongly when theyencounter a layer that ismagnetically aligned in theopposite direction,creating additionalresistance.9 12. GMR effect 10 13. GMR sensors11A photomicrograph of a GMR magnetic sensor, also known asmagnetometer is shown in figure. This sensor consists ofFour GMR resistors configured asWheatstone bridge. Two of the resitors act asReference resistors and the other two are sensing resistors. Due to external magnetic field, the sensing resistors vary inelectrical resistance causing variation in voltage at thebridge output. 14. Usage of GMR sensorsGMR sensors applications: Fast and accurate position and motion sensing of mechanicalcomponents in precision engineering and robotics. All kinds of automotive sensors for fuel handling system,anti-skid systems, speed control and navigation. Position motion sensing in computer video games. Key hole surgery and post operative care12 15. TMR effect The Tunnel magneto resistance(TMR) is a magnetoresistive effect that occurs in magnetic tunnel junctions It consists two Ferro magnet separated by a thin insulator. If the insulating wire is thin enough(typically a fewnanometers) ,electrons can tunnel from one ferro magnetinto the other13 16. TMR effect Magnetic tunnel junctions are manufactured in thin filmtechnology14 17. Application of TMR Major application of TMR is MRAM The magnetic version of random accessmemory(RAM)used in the computer is MRAM It is non-volatile- information isnt lost when thesystem is switched off.15 18. MRAM MRAM uses magnetic storage elements instead of electricused in conventional RAM16 Tunnel junctions areused to read theinformation storedin Magneto resistiveRandom AccessMemory, typicallya0 for zero pointmagnetization stateand 1 forantiparallel state 19. Drawback in current transfer 17 Attempts were made tocontrol bit writing byusing relatively largecurrents to producefields This proves unpracticalat nanoscale level 20. MRAM The spin transfer mechanism can be used to write to themagnetic memory cells Currents are about the same as read currents, requiringmuch less energy19 21. MRAM 20 MRAM promises: Density of DRAM Speed of SRAM Non-volatility like flash 22. Datta Das Spin Transistor 22 The datta das spin transistorwas first spin device proposedfor metal-oxide geometry, 1989 Emitter and collector areferromagnetic with parallelmagnetizations The gate provides magneticfield Current is modulated by thedegree of precession inelectron spin 23. Current Research 23 MATERIAL SCIENCE Many methods ofmagnetic doping SPIN TRANSPORT INSEMICONDUCTORS 24. Advantages 5 Spin lifetime is relatively long, on the order ofnanoseconds Spin currents can be manipulated Spin devices may combine logic and storagefunctionality eliminating the need for separatecomponents Magnetic storage is nonvolatile Binary spin polarization offers the possibility ofapplications as qubits in quantum computers 25. Conclusion 24 Interest in spintronics arises, in part, from the loomingproblem of exhausting the fundamental physical limits ofconventional electronics. However, complete reconstruction of industry is unlikelyand spintronics is a variation of current technology The spin of the electron has attracted renewed interestbecause it promises a wide variety of new devices thatcombine logic, storage and sensor applications. Moreover, these "spintronic" devices might lead to quantumcomputers and quantum communication based on electronicsolid-state devices, thus changing the perspective ofinformation technology in the 21st century.