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SPINTRONICS


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WHAT IS SPINTRONICS ?


Spintronics is a combination of two words
(spin & electronics)

Spintronics is a blend of electronics with spin.

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

It enhances functionality, high speed and reduced power consumption.



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 the circuit inoperable.
2. Also Quantum effects come into play at nanoscale dimensions.


PRINCIPLE


In Spintronics , information is carried by orientation of spin rather than charge.

Spin can assume one of the two states relative to the magnetic field, called spin up or spin down.

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



FABRICATION


Spintronics devices involves two different approaches for designing & manufacturing.

Giant-magneto resistance, GMR based technology

Tunnel-magneto resistance, TMR based technology

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Spintronics

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Introduction

• Spintronics is an emergent nano
technology which deals with spin
dependent properties of an electron
instead of or in addition to its charge
dependent properties.
• Where as,Conventional electronic
devices ignore the spin property and rely
strictly on the transport of the electrical
charge of electrons
• Adding the spin degree of freedom
provides new effects, new capabilities
and new functionalities
• Due to the special features it became
one of the rapidly emerging fields

Future Demands

• Moore’s Law states that the number of
transistors on a silicon chip will roughly
double every eighteen months
• In near future this spintronic devices make a
revolution than any other thing that nano
technology stirred up so far
• 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

Fundamentals of spin

• In addition to their mass and electric charge
electrons have an intrinsic quantity of angular
momentum called spin
• In a magnetic field,electrons with “spin down”
have different energies
• In an ordinary electronic circuit the spins are
oriented at random and have no effect on current
flow
• Spintronic devices create spin-polarized currents
and use the spin to control current flow

GMR

• 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

Spin Transfer

• Current passed through a magnetic field becomes
spin polarized
• This flipping of magnetic spins applies a relatively
large torque to the magnetization within the
external magnet
• This torque will pump energy to the magnet
causing its magnetic moment to precess
• If damping force is too small, the current spin
momentum will transfer to the nanomagnet,
causing the magnetization will flip
• Unwanted effect in spin valves
• Possible applications in memory writing

Spin Transistor

• Ideal use of MRAM would utilize control of
the spin channels of the current
• 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

Conclusion

Interest in spintronics arises, in part, from the looming
problem of exhausting the fundamental physical limits
of conventional electronics.
However, complete reconstruction of industry is unlikely
and spintronics is a “variation” of current technology
The spin of the electron has attracted renewed interest
because it promises a wide variety of new devices that
combine logic, storage and sensor applications.
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.