The presentation introduces to the new technology competing the The Electronics industry. It also includes various methods to implement Spintronics.

1. Introduction to Spintronics
Presented by:
Ch Ravikumar

2. Contents 0
 Introduction
 Future demands
 Spintronics
 Device working
 Electronics Vs Spintronics
 GMR and TMR
 MRAM
 Datta das Transistor
 Advantages
 Conclusion

3. Introduction 1
 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.

4. Future Demands 2
 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

5. VIDEO

6. What is Spintronics?
 Spintronics is an emerging technology that exploits both
the intrinsic spin of the electron and its associated
magnetic moment.
 It is based on the spin of the electron which exists in one
of the two states, namely spin up and spin down, with
spins either positive half or negative half.
 This type of spin creates a tiny magnetic field.
 The two possible spin states naturally represent ’0’ and
‘1’.This bit of information is called qubit.
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7. Spintronics devices working
All spintronic devices act according to the simple scheme:
1. Information is stored(written)into spins as a particular
spin orientation(up or down).
2. The spins being attached to mobile electrons, carry the
information along a wire.
3. The information is read at a terminal.
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8. Electronics Vs Spintronics
Electronics Spintronics
Power failure problem No power failure problem
“Boot up” waiting problem in
Electronic Systems
No “Boot up” waiting problem
More Power Consumption Less Power Consumption
Less Compact More Compact
Normal Speed Faster Transfer
Cheaper Costlier
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9. Effects of Spintronics
The two important effects based on spintronics are:
i. Giant Magneto Resistance (GMR) effect
ii. Tunnel Magneto Resistance (TMR) effect
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10. GMR effect
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 The discovery of GMR in 1988 is considered to be the birth
of Spintronics.
 In 1988, Alberts Fert’s group discovered GMR effect
 It is observed that when multi layers of alternate
magnetic/non-magnetic materials carrying electric current
were placed in magnetic field, they exhibit large change in
electric resistance, which is also known as magnetoresitance

11. GMR effect
 The GMR effect caused because the spin-aligned currents
from one layer are scattered strongly when they
encounter a layer that is
magnetically aligned in the
opposite direction,
creating additional
resistance.
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12. GMR effect 10

13. GMR sensors
11
A photomicrograph of a GMR magnetic sensor, also known as
magnetometer is shown in figure.
 This sensor consists of
Four GMR resistors configured as
Wheatstone bridge.
 Two of the resitors act as
Reference resistors and the other two are sensing resistors.
 Due to external magnetic field, the sensing resistors vary in
electrical resistance causing variation in voltage at the
bridge output.

14. Usage of GMR sensors
GMR sensors applications:
 Fast and accurate position and motion sensing of mechanical
components in precision engineering and robotics.
 All kinds of automotive sensors for fuel handling system,
anti-skid systems, speed control and navigation.
 Position motion sensing in computer video games.
 Key hole surgery and post operative care
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15. TMR effect
 The Tunnel magneto resistance(TMR) is a magneto
resistive effect that occurs in magnetic tunnel junctions
 It consists two Ferro magnet separated by a thin insulator.
 If the insulating wire is thin enough(typically a few
nanometers) ,electrons can tunnel from one ferro magnet
into the other
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16. TMR effect
 Magnetic tunnel junctions are manufactured in thin film
technology
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17. Application of TMR
 Major application of TMR is MRAM
 The magnetic version of random access
memory(RAM)used in the computer is –’MRAM’
 It is ‘non-volatile’- information isn’t lost when the
system is switched off.
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18. MRAM
 MRAM uses magnetic storage elements instead of electric
used in conventional RAM
16
 Tunnel junctions are
used to read the
information stored
in Magneto resistive
Random Access
Memory, typically
a”0” for zero point
magnetization state
and “1” for
antiparallel state

19. Drawback in current transfer 17
 Attempts were made to
control bit writing by
using relatively large
currents to produce
fields
 This proves unpractical
at nanoscale level

20. MRAM
 The spin transfer mechanism can be used to write to the
magnetic memory cells
 Currents are about the same as read currents, requiring
much less energy
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21. MRAM 20
 MRAM promises:
 Density of DRAM
 Speed of SRAM
 Non-volatility like flash

22. Datta Das Spin Transistor 22
 The datta das spin transistor
was first spin device proposed
for metal-oxide geometry, 1989
 Emitter and collector are
ferromagnetic with parallel
magnetizations
 The gate provides magnetic
field
 Current is modulated by the
degree of precession in
electron spin

23. Current Research 23
 MATERIAL SCIENCE
 Many methods of
magnetic doping
 SPIN TRANSPORT IN
SEMICONDUCTORS

24. Advantages 5
 Spin lifetime is relatively long, on the order of
nanoseconds
 Spin currents can be manipulated
 Spin devices may combine logic and storage
functionality eliminating the need for separate
components
 Magnetic storage is nonvolatile
 Binary spin polarization offers the possibility of
applications as qubits in quantum computers

25. Conclusion 24
 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.