53614279 Spintronics Report

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A Seminar Report OnSpintronics Technology

Session 2010-2011

Submitted To:Dr. R.S. Meena Mr. Pankaj Shukla Dept. of Electronics Engg. UCE, RTU, Kota

Submitted By:Shailendra Kumar Singh C.R.No. 07/126 Final Year, ECE UCE, RTU, Kota

Department of Electronics and Communication Engg. University College of Engineering Rajasthan Technical University, KotaPage 1

CERTIFICATE This is certify that the Seminar report titled Spintronics Technology has been submitted in partial fulfilment of the requirement for the award of Bachelor of Technology in Electronics & Communication Engineering by following student of final year B.Tech.

Shailendra Kumar Singh C.R.No:- 07/126 B.TECH. FINAL YEAR UCE, RTU, KOTA

Seminar Coordinators:Dr R S Meena & Mr Pankaj Shukla (Associate Professors) Dept. Of Electronics Engg. UCE, RTU, Kota

Head of the Department:Dr Rajeev Gupta Professor Dept. Of Electronics Engg. UCE, RTU, Kota

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ACKNOWLEDGEMENTIt gives me great pleasure to present my seminar report on Spintronics Technology. No work , however big or small, has ever been done without the contributions of others. It would be a great pleasure to write a few words, which would although not suffice as the acknowledgement of this long cherished effort, but in the absence of which this report would necessarily be incomplete. So these words of acknowledgement come as a small gesture of gratitude towards all those people, without whom the successful completion of this project would not have been possible. I would like to express deep gratitude towards Dr. R S Meena (Associate Professor of Electronics Engineering Dept., UCE, Kota) & Mr. Pankaj Shukla (Associate Professor of Electronics Engineering Dept., UCE, Kota) who gave me their valuable suggestions, motivation and the direction to proceed at every stage.They are like a beam of light for us. Their kind guidance showed us the path of life and is unforgettable. They extended towards their valuable guidance, indispensable help and inspiration at times in appreciation I offer them my sincere gratitude. Last but not least we would like to thank the Department of Electronics Engineering, UCE, Kota for providing me with the facilities to lab, and all staff members of communication lab, it would have been impossible for me to complete my project without their valuable guidance & prompt cooperation. I have tried my level best to make this seminar report error free ,but I regret for errors , if any.


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CONTENTSS. No 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Chapters Introduction Basic Principle Gaint Magnetoresistance Construction of GMR Memory Chips GMR Sensors Spin Valve GMR Spintronic Devices MRAM Spin Transistors Spintronic Scanner Conclusion Reference Page No 07 08 10 12 14 15 16 17 18 19 22 26 27

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List of FiguresS No.1. 2.

Figure NameElectron spinning Magnetic Orientation of electrons.

Page No.08 09


A GMR read head



A GMR Device



A General Magnetic Field Sensor



Spintronic Sensor



Standard Geometry for GMR based Spin Valves



GMR based Spin Valves for read head In hard drives



256 K MRAM



Spin Transistor



Spin Polarised Field Effect Transistor


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ABSTRACTSpintronics is an emergent technology that exploits the quantum propensity of the electrons to spin as well as making use of their charge state. The spin itself is manifested as a detectable 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 are inevitably faced the looming presence of quantum mechanics and are trying to exploit the spin of the electron rather than its charge. Devices that rely on the electrons spin to perform their functions form the foundations of spintronics (short for spin-based electronics), also known as magnetoelectronics. Spintronics devices are smaller than 100 nanometre in size, more versatile and more robust than those making up silicon chips and circuit elements. The potential market is worth hundreds of billions of dollar a year. Spintronics burst on the scene in 1988 when French and German physicists discovered a very powerful effect called Giant Magnetoresistance (GMR). It results from subtle electron-spin effects in ultra thin multilayers of magnetic materials, which cause huge changes in their electrical resistance when a magnetic field is applied. This resulted in the first spintronic device in the form of the spin valve. The incorporation of GMR materials into read heads allowed the storage capacity of a hard disk to increase from one to 20 gigabits. In 1997, IBM launched GMR read heads, into a market worth around a billion dollars a year. The field of spintronics is relatively young and it is difficult to predict how it will evolve. New physics is still being discovered and new materials being developed, such as magnetic semiconductors and exotic oxides that manifest an even more extreme effect called Colossal Magnetoresistance.

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Chapter 1INTRODUCTIONConventional electronic devices rely on the transport of electrical charge carriers electrons in a semiconductor such as silicon. Now, however, physicists are trying to exploit the spin of the electron rather than its charge to create a remarkable new generation of spintronic devices which will be smaller, more versatile and more robust than those currently making up silicon chips and circuit elements. Imagine a data storage device of the size of an atom working at a speed of light. Imagine a computer memory thousands of times denser and faster than todays memories and also imagine a scanner technique which can detect cancer cells even though they are less in number. The above-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 of or in addition to its charge dependent properties. Conventional electronics devices rely on the transport of electric charge carries-electrons. But there is other dimensions of an electron other than its charge and mass i.e. spin. This dimension can be exploited to create a remarkable generation of spintronic devices. It is believed that in the near future spintronics could be more revolutionary than any other technology.

As there is rapid progress in the miniaturization of semiconductor electronic devices leads to a chip features smaller than 100 nanometers in size, device engineers and physicists are inevitable faced with a looming presence of a quantum property of an electron known as spin, which is closely related to magnetism. Devices that rely on an electron spin to perform their functions form the foundations of spintronics.

Information-processing technology has thus far relied on purely charge based devices ranging from the now quantum, vacuum tube todays million transistor microchips. Those conventional electronic devices move electronic charges around, ignoring the spin that tags along that side on each electron. Page 7

Chapter 2 BASIC PRINCIPLEThe basic principle involved is the usage of spin of the electron in addition to mass and charge of electron. Electrons like all fundamental particles have a property called spin which can be orientated in one direction or the other called spin-up or spin-down like a top spinning anticlockwise or clockwise. Spin is the root cause of magnetism and is a kind of intrinsic angular momentum that a particle cannot gain or lose. The two possible spin states naturally represent 0and 1in logical operations. Spin is the characteristics that makes the electron a tiny magnet complete with north and south poles .The orientation of the tiny magnet s north-south poles depends 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.


Associated with the spin is magnetic field like that of a tiny bar magnet lined up with the 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. In a magnetic field, electrons with spin up and spin down have different energies. In an ordinary electronic circuit the spins are oriented at random and have no effect on current flow. Page 8

4. 5.


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 the sphere amount to tiny loops of electric current which creates a magnetic field. A spinning sphere in an external magnetic field changes its total energy according to how its spin vector is aligned with the spin. In some ways, an electron is just like a spinning sphere of charge, an electron has a quantity of angular momentum (spin) an associated magnetism. In an ambient magnetic field and the spin changing this magnetic field can change orientation. Its energy is dependent on how its spin vector is oriented. The bottom line is that the spin along with mass and charge is defining characteristics of an electron. In an ordinary electric current, the spin points at random and plays no role in de