SPINTRONICS…..a spin-electronics

OUTLINES

Why Spintronics?What is Spintronics?PrincipleGiant magneto resistanceElectronics Vs. SpintronicsApplicationsConclusion

Why Spintronics?

Moore’s Law: No. of Transistor doubles in every 18 months. Complexity:

Complex Chip Design & Power Loss Motivation:

Spintronics –Information is carried not by electron charge but by it’s spin.

What is Spintronics?

Spintronics is the branch of science which deals with spin of electron.

It refers to the study of the role played by the electron spin in solid state physics.

Spin of electron can be either -1/2 or +1/2. It promises new logic devices which

enhances functionality, high speed and reduced power consumption.

Principle

Spintronics is based on the spin of electrons rather than its charge.

Every electron exist in one of the 2 states-spin up and spin-down, with spins either positive half or negative half.

Principle

The two possible spin states represent ‘0’ and ‘1’ in logical operations.

The orientation of N-S axis depends on the particle ‘s axis of spin.

In ordinary materials, the up magnetic moments cancel the down magnetic moment so no surplus moment piles up.

Ferro-magnetic materials like iron, cobalt and nickel is needed for designing of spin electronic devices.

Principle

These have tiny regions called domains in which an excess of electrons have spins with axis pointing either up or down.

The domains are randomly scattered and evenly divided between majority-up and majority down.

But, an externally applied magnetic field will line up the domains in the direction of the field.This results in permanent magnet.

Principle

When a pool of spin-polarized electrons is put in a magnetic field, precession occurs.

The frequency and direction of rotation depends on the strength of magnetic field and characteristics of the material.

Thus, if a voltage pushes an electron out of gallium arsenide into zinc selenide, the electron precession characteristics change.

However, if a higher voltage pushes the electron sharply into zinc selenide, the electron precession characteristics don’t change.

Classification of Spintronics

Spin Electronics may be divided into 2 fields. 1. Semiconductor Magneto-Electronics. 2. Quantum Spin Electronics. In Semiconductor Magneto-Electronics, attempts

are being made to implement new functions by incorporating magnetic functions in semiconductor.

In quantum spin electronics, main focus is on quantum mechanical nature of spin in semiconductors.

Working These are used for quantum computing, where

electron spin will represent a bit(‘qubit’) of information.

When electron spins are aligned, this creates a large scale net magnetic moment.

Spin orientation of conduction electrons survives for relatively long time(nanoseconds) which makes spintronic device useful for memory storage and magnetic sensor applications.

Electronics vs Spintronics

One of the main advantage of spintronics over electronics is the magnets tend to stay magnetize which is sparking in the industry an interest for replacing computer’s semiconductor based components with magnetic ones, starting with the RAM.

With an all –magnetic RAM, it is now possible to have a computer that retains all the information put into it. Most importantly, there will be no ‘boot-up’ waiting period when power is turned ON.

Electronics vs Spintronics

Another promising feature of spintronics is that it doesn’t require the use of unique and specialized semiconductor, there by allowing it to work with common metals like Cu,Al,Ag.

Spintronics will use less power than conventional electronics, because the energy needed to change spin is a minute fraction of what is needed to push charge around.

Electronics vs Spintronics

Another advantage includes Non volatility: Spins don’t change when power is turned OFF.

The peculiar nature of spin and quantum theory describes it point to other wonderful possibility like various logic gates whose function can be changed billion times per second.

Applications

The Magnetic version of RAM used in computer is non volatile.

Other advantages of MRAM’s include small size, lower cost, faster speed and less power consumption, robust in extreme conditions such as high temperature, high level radiation and interference.

GMR sensors find a wide range of applications

Applications

Fast and accurate position and motion sensing of mechanical components in precision engineering and robotics.

Missile Guidance Position and motion sensing in computer

video games. Key Hole Surgery and post operative care. Automotive sensors for fuel handling system,

speed control and navigation etc..

Current Research

Material science Many methods of

magnetic doping

Spin transport in semiconductors

Conclusion

With lack of dissipation, Spintronics may be the best mechanism for creating ever-smaller devices. The potential market is enormous, In may be a 10-year timeframe, Spintronics will be on par with electronics. That’s why there’s a huge race going on around the world in exploring Spintronics.

byB.Naveen Kumar