Spintronics report

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spintronics seminar report

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  • 1. ASeminar Report OnSpintronics Technology Session 2010-2011Submitted To: Submitted By:Dr. R.S. MeenaShailendra Kumar SinghMr. Pankaj Shukla C.R.No. 07/126Dept. of Electronics Engg.Final Year, ECEUCE, RTU, KotaUCE, RTU, Kota Department of Electronics and Communication Engg. University College of EngineeringRajasthan Technical University, Kota Page 1

2. CERTIFICATE This is certify that the Seminar report titled Spintronics Technologyhas been submitted in partial fulfilment of the requirement for the awardof Bachelor of Technology in Electronics & Communication Engineeringby following student of final year B.Tech.Shailendra Kumar SinghC.R.No:- 07/126B.TECH. FINAL YEARUCE, RTU, KOTASeminar Coordinators: Head of the Department:Dr R S Meena & Mr Pankaj ShuklaDr Rajeev Gupta(Associate Professors) ProfessorDept. Of Electronics Engg. Dept. Of Electronics Engg.UCE, RTU, Kota UCE, RTU, KotaPage 2 3. ACKNOWLEDGEMENT It gives me great pleasure to present my seminar report on SpintronicsTechnology. No work , however big or small, has ever been done without thecontributions of others. It would be a great pleasure to write a few words, which would although notsuffice as the acknowledgement of this long cherished effort, but in the absence of whichthis report would necessarily be incomplete. So these words of acknowledgement comeas a small gesture of gratitude towards all those people, without whom the successfulcompletion of this project would not have been possible. I would like to express deep gratitude towards Dr. R S Meena (AssociateProfessor of Electronics Engineering Dept., UCE, Kota) & Mr. Pankaj Shukla(Associate Professor of Electronics Engineering Dept., UCE, Kota) who gave metheir valuable suggestions, motivation and the direction to proceed at every stage.Theyare like a beam of light for us. Their kind guidance showed us the path of life and isunforgettable. They extended towards their valuable guidance, indispensable help andinspiration at times in appreciation I offer them my sincere gratitude. Last but not least we would like to thank the Department of ElectronicsEngineering, UCE, Kota for providing me with the facilities to lab, and all staff members ofcommunication lab, it would have been impossible for me to complete my project withouttheir valuable guidance & prompt cooperation.I have tried my level best to make this seminar report error free ,but I regret forerrors , if any.SHAILENDRA KUMAR SINGHC.R.NO. - 07/126B. TECH. FINAL YEAR, ECEUCE, RTU, KOTAPage 3 4. CONTENTSS. No ChaptersPage No1.Introduction 072.Basic Principle083.Gaint Magnetoresistance104.Construction of GMR125.Memory Chips 146.GMR Sensors157.Spin Valve GMR 168.Spintronic Devices 179.MRAM 1810. Spin Transistors 1911. Spintronic Scanner 2212. Conclusion 2613. Reference27Page 4 5. List of FiguresS No. Figure NamePage No.1.Electron spinning082.Magnetic Orientation of electrons. 093.A GMR read head104.A GMR Device 135.A General Magnetic Field Sensor146.Spintronic Sensor157.Standard Geometry for GMR based Spin Valves168.GMR based Spin Valves for read head In hard drives 169.256 K MRAM 1810. Spin Transistor1911. Spin Polarised Field Effect Transistor 20Page 5 6. ABSTRACTSpintronics is an emergent technology that exploits the quantum propensity of theelectrons to spin as well as making use of their charge state. The spin itself is manifested as adetectable weak magnetic energy state characterised as spin up or spin down. Conventional electronic devices rely on the transport of electrical charge carriers electrons in a semiconductor such as silicon. Now, however, device engineers and physicists areinevitably faced the looming presence of quantum mechanics and are trying to exploit the spin ofthe electron rather than its charge. Devices that rely on the electrons spin to perform theirfunctions form the foundations of spintronics (short for spin-based electronics), also known asmagnetoelectronics. Spintronics devices are smaller than 100 nanometre in size, more versatile andmore robust than those making up silicon chips and circuit elements. The potential market is worthhundreds of billions of dollar a year. Spintronics burst on the scene in 1988 when French and German physicists discovereda very powerful effect called Giant Magnetoresistance (GMR). It results from subtle electron-spineffects in ultra thin multilayers of magnetic materials, which cause huge changes in their electricalresistance when a magnetic field is applied. This resulted in the first spintronic device in the formof the spin valve. The incorporation of GMR materials into read heads allowed the storage capacityof a hard disk to increase from one to 20 gigabits. In 1997, IBM launched GMR read heads, into amarket worth around a billion dollars a year. The field of spintronics is relatively young and it is difficult to predict how it willevolve. New physics is still being discovered and new materials being developed, such as magneticsemiconductors and exotic oxides that manifest an even more extreme effect called ColossalMagnetoresistance.Page 6 7. Chapter 1 INTRODUCTIONConventional electronic devices rely on the transport of electrical charge carriers electrons in asemiconductor such as silicon. Now, however, physicists are trying to exploit the spin of theelectron rather than its charge to create a remarkable new generation of spintronic deviceswhich will be smaller, more versatile and more robust than those currently making up siliconchips and circuit elements.Imagine a data storage device of the size of an atom working at a speed of light. Imagine acomputer memory thousands of times denser and faster than todays memories and also imaginea scanner technique which can detect cancer cells even though they are less in number. Theabove-mentioned things can be made possible with the help of an exploding science Spintronics.Spintronics is a technology which deals with spin dependent properties of an electron instead ofor in addition to its charge dependent properties. Conventional electronics devices rely on thetransport of electric charge carries-electrons. But there is other dimensions of an electron otherthan its charge and mass i.e. spin. This dimension can be exploited to create a remarkablegeneration of spintronic devices. It is believed that in the near future spintronics could be morerevolutionary than any other technology.As there is rapid progress in the miniaturization of semiconductor electronic devices leads to achip features smaller than 100 nanometers in size, device engineers and physicists are inevitablefaced with a looming presence of a quantum property of an electron known as spin, which isclosely related to magnetism. Devices that rely on an electron spin to perform their functionsform the foundations of spintronics.Information-processing technology has thus far relied on purely charge based devices rangingfrom the now quantum, vacuum tube todays million transistor microchips. Those conventionalelectronic devices move electronic charges around, ignoring the spin that tags along that side oneach electron.Page 7 8. Chapter 2 BASIC PRINCIPLEThe basic principle involved is the usage of spin of the electron in addition to mass and charge ofelectron. Electrons like all fundamental particles have a property called spin which can beorientated in one direction or the other called spin-up or spin-down like a top spinninganticlockwise or clockwise. Spin is the root cause of magnetism and is a kind of intrinsic angularmomentum that a particle cannot gain or lose. The two possible spin states naturally represent0and 1in logical operations. Spin is the characteristics that makes the electron a tiny magnetcomplete with north and south poles .The orientation of the tiny magnet s north-south polesdepends on the particles axis of spin.Fundamentals of spin:1. In addition to their mass, electrons have an intrinsic quantity of angular momentum called spin, almost of if they were tiny spinning balls.2. Associated with the spin is magnetic field like that of a tiny bar magnet lined up withthe spin axis. .Fig.1. Electron spinning2. Scientists represent the spin with a vector. For a sphere spinning west to east, the vector points north or up. It points south or down for the spin from east to west.4. In a magnetic field, electrons with spin up and spin down have different energies.5. In an ordinary electronic circuit the spins are oriented at random and have no effect on current flow.Page 8 9. 6. Spintronic devices create spin-polarized currents and use the spin to control current flow.Imagine a small electronically charged sphere spinning rapidly. The circulating charges in thesphere amount to tiny loops of electric current which creates a magnetic field. A spinning spherein an external magnetic field changes its total energy according to how its spin vector is alignedwith the spin. In some ways, an electron is just like a spinning sphere of charge, an electron has aquantity of angular momentum (spin) an associated magnetism. In an ambient magnetic field andthe spin changing this magnetic field can change orientation. Its energy is dependent on how itsspin vector is oriented. The bottom line is that the spin along with mass and charge is definingcharacteristics of an electron. In an ordinary electric current, the spin points at random and playsno role in determining the resistance of a wire or the amplification of a transistor circuit.Spintronic devices in contrast rely on the differences in the transport of spin-up and spin-downelectrons.Fig 2. Magnetic Orientation of electronsPage 9 10. Chapter 3 Giant MagnetoresistanceElectrons like all fundamental particles have a property called spin which canbe orientated in one direction or the other called spin-up or spin-down like a topspinning anticlockwise or clockwise. When electron spins are aligned (i.e. all spin-up or allspin-down) they create a large-scale net magnetic moment