Presentation By

ANNAMACHARIYA INSTITUTE OF TECHNOLOGY & SCIENCES (Autonomous) New Boyanapalli,Rajampet

•Introduction•GMR•Devices•Advantages and disadvantages•conclusion

Spintronics is a NANO technology which deals with spin dependent properties of an electron instead of charge dependent properties

•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) same thing as the electron positive or negative charge correspond 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

• The overall resistance is low for parallel allignment

• The overall resistance is high for anti parallel allignment

• Red heads are modern hard drives are based n the gmr effect

Gaint Magnetoresistance (GMR) The basic GMR device consists of a layer of non -magnetic metal between two two magnetic layers. A current passes through the layers consisting of spin up or spin down electrons. Those oriented in the same direction as the electron spins in a magnetic layer pass 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 transistor

3. Quantum Computer

•MRAM uses magnetic storage elements instead of electric used in conventional RAM

•Tunnel junctions are used to read the information stored in Magnetoresistive Random Access Memory, typically a”0” for zero point magnetization state and “1” for antiparallel state•Other advantage of MRAM include smaller size ,lower cost,faster speed and less power consumption.

SRAM VS DRAM VS MRAM

•SRAM

•DRAM

•MRAM

•Fast read and write speed•Low power

•High density•Fast speed and write speed

•Fast read and write speed•Low power•High density•Non volatile

•Volatile•Low density

•Volatile•High power

•none

•Current passed through a magnetic field becomes spin polarized

•Spin transistors would allow control of the spin current in the same manner that conventional transistors can switch charge currents

•Using arrays of these spin transistors, MRAM will combine storage, detection, logic and communication capabilities on a single chip

•This will remove the distinction between working memory and storage, combining functionality of many devices into one

•The Datta Das Spin Transistor was first spin device proposed for metal-oxide geometry, 1989

•Emitter and collector are ferromagnetic with parallel magnetizations

•The gate provides magnetic field

•Current is modulated by the degree of precession in electron spin

A Quantum computer, in contrast, lies on encoding information within t quantum bits or qubits, each of which can exist in a superposition of ‘0’ and ‘1’.

PLASTIC MEMORY:

•All the moving electrons inside a sample plastic spin in same direction-an effect called spin polarisation that could yeild the plastic memories•The achieving of spin polarisation happen using magnetic field

•This is first step converting plastic into device

•Plastic spintronic devices would weigh less ,cost less to manifacture.

•Plastic—vanadium tetra cyanoethanide

ELECTRONIC DEVICES

•Based on properties of charge of the electron

•Classical property

•Meterials:conductors and semi conductors

•Speed is limited

•Power dissipation is high

SPINTRONIC DEVICES

•Based on intrensic property spin electron

•Quantum property

•Materials:ferromagnetic materials

•Speed high

•Power dissipation is low

Advantages

•low power consumption

• Multi purpose devices (amplifiers)

•No electric current required•Faster Devices

•Larger storage capacity

•Smaller devices

Disadvantages

•Controlling the spin for long distances•Combining techniques between the semiconductor and magnetic recording industry•Difficult to inject and measure spin in silicon•Silicon causes electrons to lose their spin state

This technology will exploit the spin of the electron and create new devices and circuits which could be more beneficial in future by providing devices like memories for data base accessing with the speed of light.

The devices of this technology are very useful for transaction processing and for scientific number crunching.

ByN balaji Krishna11701A0412