SPINTRONICS

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SPINTRONICS
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The Future Belongs To SpintronicsOUTLINE

• Why Spintronics?
• What is Spintronics?
• Principle
• Fabrication Working of spin devices
• Electronics Vs. Spintronics
• Applications
• Conclusion

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Why Spintronics?
Moores 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 its
spin.
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What is Spintronics?
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 and
possible devices that specifically exploits spin
properties of electrons instead of its
charge. It promises new logic devices which
enhances functionality, high speed and reduced
power consumption.
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Principle
Spintronics is based on the spin of electrons
rather than its charge. Every electron exist in
one of the two states- spin-up and spin-down,
with spins either positive half or negative
half. In other words, electrons can rotate
either clock wise or anti-clockwise around its
own axis with constant frequency. The two
possible spin states represent 0 and 1 in
logical operations.
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Principle
Spin is a characteristic that makes an electron
a tiny magnet with north and south poles. The
orientation of north-south axis depends on the
particles 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.
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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 a permanent magnet.
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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 dont change.
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Principle
N-type materials rely on electrons to carry
current where as P-type materials rely on
holes. As the materials are of two different
carrier types, an electric field is formed around
their junction. This field is strong enough to
pull a pool of spin coherent electrons from GaAs
immediately into ZnSe, where coherence persist
for 100 of nanoseconds. Thus, spin can be moved
from one kind of semiconductor to another without
the need for external electric fields.
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Fabrication

• Spintronics devices involves two different
  approaches for designing manufacturing.
• Perfecting the existing giant magneto resistance,
  GMR based technology by developing new materials
  with larger spin polarization.
• Finding the novel ways of both generation and
  utilization of spin polarized current.
• The later one is a effective method.

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Working
All spintronic devices acts according to the
simple scheme The information is stored
(written) into spins as a particular spin
orientation (up or down). The spins, being
attached to mobile electrons, carry information
along a wire and the information is read at a
terminal. Spin orientation of conduction
electrons survives for relatively long time
(nanoseconds, compared to tens of femtoseconds
during which electron moment decays) which makes
spintronic device useful for memory storage and
magnetic sensor applications.

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Working
These are used for quantum computing where
electron spin will represent a bit (called
qubit) of information. When electron spins are
alligned, this creates a large scale net magnetic
moment. The basic GMR device is a 3 layer
sandwich of magnetic metal (such as cobalt) with
a non-magnetic metal filling (such as silver). A
current passes through the layers consisting of
spin up and spin down electrons.

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The electrons oriented in the same direction as
the electron spin in the magnetic layer pass
through quite easily while those oriented in the
opposite direction are scattered. If
orientation of one of the magnetic layers is
changed by the presence of a magnetic field, the
device will act as a filter or a spin valve
letting through more electrons when spin
orientation in the two layers are the same and
fewer electrons when spin orientation are
oppositely alligned.
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The electrical resistance of the device can
therefore be changed dramatically. The above
diagram depicts the nature of the spin valve when
the two layers are oppositely alligned.
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Electronics vs. Sprintronics

• 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 computers 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.

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Electronics vs. Sprintronics

• Another promising feature of spintronics is that
  it doesnt 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.

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Electronics vs. Sprintronics

• Another advantage includes Non-volatility Spins
  dont 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.

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Application

• The Magnetic version of RAM used in computer is
  nonvolatile.
• Other advantages of MRAMs include small size,
  lower cost, faster speed and less power
  consumption, robust in extreme condition such as
  high temperature, high level radiation and
  interference.

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Applications

Magnetic RAM
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Applications

• GMR sensors find a wide range of 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.

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Applications
Spin Valve Transistors It is based on magneto
resistance, found in multi layers (Co-Cu-Co)
forming the base region. The collector current
becomes strongly field dependent, the extreme
magneto sensitivity makes the transistor, an
interesting device for high technology hard disks
and magnetic RAMs.

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Conclusion

With lack of dissipation, spintronics may be the
best mechanism for creating ever-smaller devices.
The potential market is enormous, In maybe 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.
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The Future Belongs To SpintronicsAny
Queries?

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Thank you all
The Future Belongs To Spintronics