Presentation By

•Introduction•GMR•Spintronics V/s Electronics•Future Demand•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

Basic Principle• 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.

Continued…

• Utilizes the bizarre property of spin of electron.

• Intrinsic angular momentum is spin.

• Two arbitrary orientations, and its magnitudes are ± ħ / 2 (ħ is Plank constant).

• Directional and coherent motion of electron spin circulates a spin current, which will carry or transport information and control quantum spin in an spintronic device.

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

• When the magnetization of the two outside layers is aligned, lowest resistance

• Conversely when magnetization vectors are antiparallel, high R

• Small fields can produce big effects

• parallel and perpendicular current

Gaint Magnetoresistance (GMR) The basic GMR device consists of a layer of non -magnetic metal between two

magnetic layers. A current consisting of spin-up and spin-down electrons is passed through

the layers. 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.

Spin Valve GMR

Spin Valve GMR

If the orientation of one of the magnetic layers can easily be changed by the presence of a magnetic field then the device will act as a filter, or ‗spin valve‘,

letting through more electrons when the spin orientations in the two layers are the same and fewer when orientations are oppositely aligned. The electrical

resistance of the device can therefore be changed dramatically.

•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

Tunnel magnetoresistance(TMR)

Tunnel magnetoresistance (TMR) is a magnetoresistive effect

that occurs in a magnetic tunnel junction (MTJ), which is a

component consisting of two ferromagnets separated by a thin

insulator..

ELECTRONICS V/S SPINTRONICS

Electronic Devices

• Based on properties of charge of the electron  

• Classical property  

• Materials: conductors and semiconductors  

• Based on the number of charges and their energy

• Speed is limited and power dissipation is high

Spintronic Devices

• Based on intrinsic property spin of electron

•  Quantum property

•  Materials: ferromagnetic materials  

• Two basic spin states; spin-up and spindown.

• Based on direction of spin and spin and spin coupling, high speed  

•Moore’s Law states that the number of transistors on a silicon chip will roughly double every eighteen months

•By 2008, it is projected that the width of the electrodes in a microprocessor will be 45nm across

•As electronic devices become smaller, quantum properties of the wavelike nature of electrons are no longer negligible

•Spintronic devices offer the possibility of enhanced functionality, higher speed, and reduced power consumption

Advantages

.low power consumption

. Multi purpose devices (amplifiers).No electric current required.Faster Devices.Larger storage capacity.Smaller devices

Disadvantages

.Controlling the spin for longdistances.Combining techniques between thesemiconductor and magneticrecording 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.

Moreover, these "spintronic" devices might lead to quantum computers and quantum communication based on electronic solid-state devices, thus changing the perspective of information technology in the 21st century