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SPINTRONICS

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TOPICS OF DISCUSSION

1) SPINTRONICS2) HISTORY3) THEORY4) OPERATION5) SPINTRONIC DEVICES6) ADVANTAGES7) LOOPHOLES 8) CONCLUSION

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SPINTRONICSWhat is SPINTRONICS?

•Spintronics is a new branch of electronics in which electron spin, in addition to charge, is manipulated to yield a desired electronic outcome. The spin itself is manifested as a detectable weak magnetic energy state characterized as “spin up” or “spin down”.

•Conventional electronic devices rely on the transport of electrical charge carriers – electrons in a semiconductor such as silicon.

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CONTD…

• Devices that rely on the electron’s spin to perform their functions form the foundations of spintronics (spin-based electronics), also known as magneto electronics.

• Spintronics devices are smaller than 100 nm in size, more versatile and more robust than those making up silicon chips and circuit elements.

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HISTORY

• 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.

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THEORY

• SPINTRONICS,short for spin electronics,is the study of electron spin in materials in order to better understand its behavior,with the hope of developing an entirely new generation of microelectronic devices.

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CONTD…

• An electron is just like a spinning sphere of charge

• The electron has a quantum property, called

spin,that makes it behave almost as if it were a magnet twirling about the axis connecting its north and south poles.Electron can have spins oriented in different directions

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CONTD…

• A magnetic field causes an electron to swivel like a needle of a compass to line up with the field(left).But the spin axis precesses like a wobbling top(right).

• When the magnetic field is removed,the electron stops precessing and locks the orientation of its spin.

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CONTD…

• The spin of the electron has three states to it; up, down, and in between.

• In today’s world of computers the spin is ignored and you have either on/off, 0/1, or up/down but with the spin of the electron you can have many states and not be limited with those two states.

• Because of these many states information can be processed a whole lot faster if an electrons spin carries data.

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SPIN OF ELECTRON

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OPERATION

• Miniaturization has always been a part of rapidly developing electronic industry. But there is a limit to the number of transistor or other electronic component that can be cramped on a single chip

• . Besides this, small electronic devices are plagued by a big problem of energy loss or dissipation, as signals pass from one transistor to the next transistor. So the only solution to overcome this problem is to find some method that takes both the problem into account.

• Apart from miniaturization another problem with devices is that their working is based on use of electronic charges. This working has several disadvantages; power failure being one of them. In case of a power cut, information stored by electronic charges is lost. Hence, before a computer is turned off, all the work is saved on the hard disk.

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CONTD…

• `Spintronics` or Spin electronics, is one of the solutions to overcome this problem.

• These Spintronic devices will work in following manner: (1) Information will be stored (written) into spins as a particular spin orientation (up or down) (2) The spins, being attached to mobile electrons, will carry the information along a wire (3) The information will be read at a terminal.

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SPINTRONIC DEVICES

• The spintronic devices have opened us to a whole new network of high –tech technology.

• Some of these devices are:• MAGNETIC RANDOM ACCESS

MEMORY(MRAM)

• TRANSPINNOR

• MAGNETIC TUNNEL JUNCTION

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MTJ

• Consists of two layers of magnetic metal, such as cobalt-iron, separated by an ultra thin layer of insulator, typically aluminum oxide with a thickness of about 1 nm.

• The insulating layer is so thin that electrons can tunnel through the barrier if a avoltage is applied between the two metal electrodes.

• The current depends on the relative orientation of magnetizations of the two ferromagnetic layers, which can be changed by an applied magnetic field. This phenomenon is called tunneling magneto resistance (TMR).

Antiparallelmagnetizations

Parallelmagnetizations

Ferromagnet

Ferromagnet

I nsulator

Resistance: R

R

RRTMR=

Tunneling current

Resistance: R

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MRAM

Magnetic Tunnel Junctions

• MRAM stands for magnetic random access memory.

• It places the magnetic domains on the surface of a silicon chip and places a magneto-resistive sensor beneath everyone of them.

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CONTD…

• Just like a hard disk,the information stored in the magnetic domains is non volatile.It is not lost when the power goes off.

• The two main concept that govern MRAM technology are:– Giant Magnetoresistance

effect(GMR)– The Tunneling Magneto

Resistive effect(TMR)GMR Valves

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TRANSPINNORS

• A Transpinnor is a bridge of four electrically connected GMR films whose resistance is controlled by the magnetic field from the current in one of more input strip lines electrically isolated from GMR films.

• Transpinnors can be used as selection matrix elements for magnetic memories,for logic elements of all kinds(e.g..AND,OR,NAND , NOT),for amplifiers,differential amplifiers.

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ADVANTAGES

• The various advantages of spintronics is as follows:

• Does not require unique and specialized semiconductors;can be implemented with common metals such as Cu,Al.

• Spintronic devices consume less power.• The memory remains non-volatile.

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LOOPHOLES

• The various disadvantages are as follows:

• The fringe fields generated interfere with the neighboring elements.

• Hazards of holes• Much remains to be understood about

the behavior of electron spins in materials for technological applications

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CONCLUSION

• Spintronics is a rapidly emerging field of science and technology that will most likely have a significant impact on the future of all aspects of electronics as we continue to move into the 21st century.

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CONTD…

• Conventional electronics are based on the charge of the electron. Attempts to use the other fundamental property of an electron, its spin, have given rise to a new, rapidly evolving field, known as spintronics, an acronym for spin transport electronics that was first introduced in 1988.

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