Basic electrical and electronic engineering

1. Spintronics
“A Spin to Remember”
Presented By :- Presented To :-
Md. Saown Khan Mr. Tariqul Islam Shakil
ID:153-23-4454 Department of EEE
Lecturer
Daffodil international university

3. Outline
• Spintronics basics
• The giant magneto resistance
• Applications of GMR
• Spin devices
• Injections & detection of spin
• The MRAM
• Recent trends

4. What is Spintronics?
• Utilizes the bizarre
property of spin of
electron.
• Intrinsic angular
momentum is spin.
• Two arbitrary
orientations, and its
magnitudes are ± ħ / 2 (ħ
is Plank constant).
• Directional and coherent
motion of electron spin
circulates a spin current,
which will carry or
transport information and
control quantum spin in
an spintronic device.

5. 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.

6. Moore’s law

7. Combining the best of both worlds
Ferro magnets
• Stable Memory
• Fast switching
• High ordering temp
• Spin transport
• Technological base
(magnetic recordings)
Semiconductors
• Bandgap engineering
• Carrier density & type
• Electrical gating
• Long spin lifetime
• Technological base
(Electronics)

8. The Giant Magneto Resistance
• A Nano scale phenomena .
• Giant refers to giant change in resistance due to current.
• It is a quantum mechanical magneto resistance effect
observed in thin-film structures composed of alternating
ferromagnetic and non-magnetic layers.

11. Magnetic tunneling junction
• Like GMR but better.
• More sensitive
• Multilayer junction filter
• Quantum mechanical
principle
• Tunneling effect
• 2 layers of magnetic
metal, separated by an
ultrathin layer of
insulator, about 1 nm.

13. Spin transistor
• Supriyo Datta and Biswajit Das Transistor

14. Spin injection into silicon
• Injection

15. Spin manipulation
• Hanle effect :- Suppression of spin accumulation
Ferro magnet
Oxide
B
Spin
Silicon

16. Magnetic field along the spin
• Hanle curve for a) Ge , b) Si

17. Detection of spin polarization in
silicon
Ferro magnet Al2O3
Tunnel barrier
e-
n type Silicon
Spin accumulation
u
Tunnel resistance in proportional to u
I = G * ( V - u/2)
I = G * ( V + u/2)

18. MRAM
Magneto resistive RAM
Reading process
• Measurement of the bit
cell resistance by
applying a current in the
‘bit line’
• Comparison with a
reference value mid-
way between the bit
high and low resistance
values

19. MRAM
Magneto resistive RAM
Writing process
• Currents applied in both
lines : 2 magnetic fields
• Both fields are necessary
to reverse the free layer
magnetization
• When currents are
removed : Same
configuration

20. 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

21. MRAM vs …..

22. MRAM
Magneto resistive RAM
• MTJ test structures developed at SPINTEC: the die area with 1x5 μm
• 0.2 μm width isolated MTJ element after etch

23. Advantages 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.

24. Conclusion
• Spin property of electrons are yet to mastered.
• Researcher and scientist are taking keen interest.
• Universities and electronic industries collaborating .
• Span of last two decade major milestones.
• It holds vast opportunities for physics , material & device
engineering & technology
• Last year PTB, Germany, have achieved a (2GBit/s)
write cycle
• Potential of the field is colossal and
continuous development is required.