one of the ways in which quantam mechanics is being in limelight

1. Spintronics
SLIDE 1

2. Introduction
 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
SLIDE 2

3. Future Demands
 Moore’s Law states that the number of
transistors on a silicon chip will roughly
double every eighteen months
 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
SLIDE 3

4. Spintronics = Spin-based electronics
 Spintronics is a NANO technology
which deals with spin dependent
properties of an electron instead of
charge dependent properties
 Spintronics uses electron spins
in addition to or in place of the
electron charge.
SLIDE 4

5. Principle
 Every electron exist in one of the two states spin-up
and spin-down, with spins either positive half or
negative half.
SLIDE 5
 Origin of the spin is electron’s intrinsic property
“angular momentum”
 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
particle’s axis of spin.

6. Principle
 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.
 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.
SLIDE 6

7. Principle
SLIDE 7
1. These have tiny regions called domains in
which an excess of electrons have spins with
axis pointing either up or down.
2. The domains are randomly scattered and
evenly divided between majority-up and
majority-down.
3. But, an externally applied magnetic field will
line up the domains in the direction of the
field. This results in a permanent magnet.

8. Gaint Magnetoresistance (GMR)
SLIDE 8
 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.

9. Advantage Of 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.
SLIDE 9

10. Applications
Spin Polarized Feild Effect
Transistor (Spin-FET)
SLIDE 9
In these devices a non magnetic layer which is
used for transmitting and controlling the spin
polarized electrons from source to drain plays
a crucial role. For functioning of this device
first the spins have to be injected from source
into this non-magnetic layer and then
transmitted to the collector. These
non-magnetic layers are also called as
semimetals, because they have very large spin
diffusion lengths. The injected spins which are
transmitted through this layer start precessing
as illustrated in Figure before they reach the
collector due to the spin-orbit coupling effect.

11. 2. MRAM
 The Magnetic version of
RAM used in computer is
nonvolatile.
 Other advantages of
MRAM’s include small
size, lower cost, faster
speed and less power
consumption, robust in
extreme condition such as
high temperature, high level
radiation and interference.
SLIDE 10

12. MRAM SLIDE 11
 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.

13. MRAM
Magneto resistive RAM
Array structure of
MRAM
 Reading: transistor of
the selected bit cell
turned ‘on’ + current
applied in the bit line
 Writing: transistor of
the selected bit cell
turned ‘off’ + currents
applied in the bit and
word lines
 Need of 2 magnetic
fields for writing
SLIDE 12

14. SLIDE 13
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