1. The document describes a technical seminar on spintronic technology submitted by a student. 2. Spintronics is an emerging nanotechnology that uses the spin of electrons in addition to or instead of their charge to build devices. 3. One application is magnetoresistive random access memory (MRAM), a new type of non-volatile memory that could replace traditional RAM.

1. TECHNICAL SEMINAR
ON
SPINTRONIC TECHNOLOGY
Submitted in Partial Fulfillment of the requirement
For the award of degree of Bachelor of Technology
In
ELECTRONICS AND COMMUNICATION ENGINEERING
Submitted by
A. DIVYAJYOTHI 096L1A0405
Under the Esteemed coordinator of
D.V.RAJESHWAR RAJU
(Assistant Professor)
PRASAD ENGINEERING COLLEGE
(Approved by AICTE and Affiliated to JNTU Hyderabad)
JANGAON, WARANGAL, 506167(AP)
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2. Certificate
This is to certify that the mini project report entitled SPINTRONIC TECHNOLOGY is
being submitted by A. DIVYAJYOTHI in partial fulfillment of the requirement for the award of
degree in Bachelor of Technology in Electronics and Communication Engineering during the
period 2009-2013. This is a record of students own work carried out by them under our
supervision and guidance.
The matter enclosed in this project report has not been submitted for the award of any
other Degree.
D.V.RAJESHWAR RAJU. B.SWAMY.
Coordinator Head of the Department
ACKNOWLEDGEMENT
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3. My special thanks to Mrs.D.RAMADEVI, Principal and management for
providing all the facilities required for completing this seminar.
We are very grateful to Mr.B.SWAMY, Head of the department, and
ELECTRONICS AND COMMUNICATION ENGINEERING for his inspiring guidance
and advice throughout the project.
We owe our deep depth of gratitude to our coordinator D.V.RAJESHWAR RAJU,
Assistant professor for his valuable guidance and constant encouragement at each
stage of this project work.
ABSTRACT
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4. Keywords:(GMR)
“Spintronics” is an emergent NANO technology, which uses the spin of an electron
instead of or in addition to the charge of an electron. Electron spin has two states either “up” or
“down”. Aligning spins in material creates magnetism. Moreover, magnetic field affects the
passage of spin-up and spin-down electrons differently the paper starts with the detail description
of the fundamentals and properties of the spin of the electrons. It proceeds with a note on
magneto resistance, the development of Giant Magneto resistance (GMR) and devices like
Magneto Random Access Memory, which are the new version of the traditional RAMs. It
describe how this new version of RAMs which can revolutionize the memory industry. There is
also detailed explanation of the way, how this revolution can increase the data density in our
memory systems. It is followed by an account of new Spin Field Effect Transistors. It also
specifies the differences between electronic devices and spintronic devices. It also gives the
hurdles due to the presence of holes. This paper also discusses about a quantum computer, which
uses qubits rather than normal binary digits for computations. It also gives the hurdles due to the
presence of holes. Finally it ends with a note on why we should switch on this technology. Ran
road track and conveyor belts kept the Ford’s assemble line running. At that time, his method of
production was lauded and was considered most efficient. But that ford’s assembly plant, which
was only eulogized in his time, will look strange to those who were born and raised up in the
21st century. Because the machines in the next 50 years will get increasingly smaller – so small
that thousands of machines will fit into the full stop at the end of this line. This branch of
engineering which deals with things smaller than 100 nanometers is termed as Nanotechnology.
Eric Dexler first coined it in his book “engine of creation”.
In this paper we will discuss about a field of Nanotechnology, which is believed to
replace conventional electronics in the near future, i.e. “spintronics”.
Chapter-1
INTRODUCTION
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5. 1.1 SPINTRONICS
Imagine a data storage device of the size of an atom working at a speed of light. Imagine
a microprocessor whose circuits could be changed on the fly. One minute is could be optimized
for data base access. The next for transaction processing and the next for scientific number
crunching. Finally, imagine a computer memory thousands of times denser and faster than
today’s memories.
The above-mentioned things can be made possible with the help of an exploding science
– “spintronics”. Spintronics is a NANO technology which deals with spin dependent properties
of an electron instead of or in addition to its charge dependent properties, Conventional
electronics devices rely on the transport of electric charge carries electrons. But there is other
dimension of an electron other than its charge and mass i.e. spins. This dimension can be
exploited to create a remarkable generation of spintronic devices. It is believed that in the near
future spintronics could be more revolutionary than any other thing that nanotechnology has
stirred up so far.
1.2 WHY IS IT GOING TO BE ONE OF THE RAPIDLY EMERGING
FIELDS?
As there is rapid progress in the miniaturization of semiconductor electronic devices
leads to a chip features smaller than 100 nanometers in size, device engineers and physists are
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6. inevitable faced with a looming presence of a quantum property of an electron known as spin,
which is closely related to magnetism. Devices that rely on an electron spin to perform their
functions from the foundations of spintronics. Information-processing technology has thus far
relied on purely charge based devices ranging from the now quantum, vaccume tube today’s
million transistor microchips. Those conventional electronic devices move electronic charges
around, ignoring the spin that tags along that side on each electron.
CHAPTER-2
ELECTRON SPIN
2.1 FUNDAMENTALS OF SPIN
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7. 1. In addition to their mass and electric charge, electrons have an intrinsic quantity of angular
momentum called spin, almost of if they were tiny spinning balls.
2. Associated with the spin is magnetic field like that of a tiny bar magnet lined up with the spin
axis.
3. Scientists represent the spin with a vector. For a sphere spinning “west to east”, the vector
points “north” or “up”. It points “down” for the opposite spin.
4. In a magnetic field, electrons with “spin up” and “spin down” have different energies.
5. In an ordinary electronic circuit the spins are oriented at random and have no effect on current
low.
6. Spintronic devices create spin-polarized currents and use the spin to control current flow.
Electrons like all fundamental particles have a property called spin, which can be oriented in one
direction, or the other called spin-up or spin-down. Magnetism is an intrinsic Physical property
associated with the spins. An intuitive notion of how an electron spins is suggested below.
Imagine a small electronically charged sphere spinning rapidly. The circulating charges
in the sphere amount to tiny loops of electric current which creates a magnetic field.. a spinning
sphere in an external magnetic field changes its total energy according to how its spin vector is
aligned with the spin. In some ways, an electron is just like a spinning sphere of charge, an
electron has a quantity of angular momentum (spin) an associated magnetism. In an ambient
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8. magnetic field and the spin changing this magnetic field can change orientation. Its energy is
dependent on how its spin vector is oriented. The bottom line is that the spin along with mass
and charge is defining characteristics of an electron,. In an ordinary electric current, the spin
points at random and plays no role in determining the resistance of a wire or the amplification of
a transistor circuit. Spintronic devices in contrast rely on the differences in the transport of spin-
up and spindown electrons.
CHAPTER-3
GMR
3.1 GIANT MAGNETO RESISTANCE
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9. Magnetism is the integral part of the present day’s data storage techniques. Right from
the Gramophone disks to the hard disks of the super computer magnetism plays an important
role. Data is recorded and stored as tiny areas of magnetized iron or chromium oxide. To access
the information, a read head detects the minute changes in magnetic field as the disk spins
underneath it. In this way the read heads detect the data and sent it to the various succeeding
circuits. The magneto resistant devices can sense the changes in the magnetic field only to a
small extent, which is appropriate to the existing memory devices. When we reduce the size and
increase data storage density, we reduce the bits, so our sensor also has to be small and maintain
very, very high sensitivity. The thought gave rise to the powerful effect called “GIANT
MAGNETORESISTANCE” OR (GMR). Giant magneto resistance (GMR) came into picture in
1988, which lead the rise of spintronics. It results from subtle electron-spin effects in ultra-thin
‘multilayer’ of magnetic materials, which cause huge changes in their electrical resistance when
a magnetic field is applied. GMR is 200 times stronger than ordinary magneto resistance. It was
soon realized that read heads incorporating GMR materials would be able to sense much smaller
magnetic fields, allowing the storage capacity of a hard disk to increase from 1 to 20 gigabits.
3.2 CONSTRUCTION OF GMR
The basic GMR device consists of a three-layer sandwich of a magnetic metal such as
cobalt with a nonmagnetic metal filling such as silver. Current passes through the layers
consisting of spin-up and spin-down electrons. 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. If the orientation of one of the magnetic layers can easily be changed by
the presence of a magnetic field then the device will act as a filter, or ‘spin valve’, letting through
more electrons when the spin orientations in the two layers are the same and fewer when
orientations are oppositely aligned. The electrical resistance of the device can therefore be
changed dramatically. In an ordinary electric Current, the spin points at random and plays no role
in determining the resistance of a wire or the amplification of a transistor circuit. Spintronic
devices, in contrast, rely on differences in the transport of “spin up” and “spin down” electrons.
When a current passes through the Ferro magnet, electrons of one spin direction tend to be
obstructed.
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10. A ferromagnetic can even affect the flow of a current in a nearby nonmagnetic metal. For
example, in the present-day read heads in computer hard drives, wherein a layer of a
nonmagnetic metal is sandwiched between two ferromagnetic metallic layers, the magnetization
of the first layer is fixed, or pinned, but the second ferromagnetic layer is not. As the read head
travels along a track of data on a computer disk, the small magnetic fields of the recorded 1’s and
0`s change the second layer’s magnetization back and forth parallel or anti parallel to the
magnetization of the pinned layer. In the parallel case, only electrons that are oriented in the
favored direction flow through the conductor easily. In the anti parallel case, all electrons are
impeded. The resulting changes in the current allow GMR read heads to detect weaker fields
than their predecessors; so that data can be stored using more tightly packaged magnetized spots
on a disk.
CHAPTER-4
SPINTRONIC DEVICES
4.1 MRAM (MAGNETORESISTIVE RANDOM ACCESS
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11. Magnetism is the integral part of the present day’s data storage techniques. Right from
the Gramophone disks to the hard disks of the super computer magnetism plays an important
role. Data is recorded and stored as tiny areas of magnetized iron or chromium oxide. To access
the information, a read head detects the minute changes in magnetic field as the disk spins
underneath it. In this way the read heads detect the data and sent it to the various succeeding
circuits. The magneto resistant devices can sense the changes in the magnetic field only to a
small extent, which is appropriate to the existing memory devices. When we reduce the size and
increase data storage density, we reduce the bits, so our sensor also has to be small and maintain
very, very high sensitivity. The thought gave rise to the powerful effect called “GIANT
MAGNETORESISTANCE” OR (GMR). Giant magneto resistance (GMR) came into picture in
1988, which lead the rise of spintronics. It results from subtle electron-spin effects in ultra-thin
‘multilayer’ of magnetic materials, which cause huge changes in their electrical resistance when
a magnetic field is applied. GMR is 200 times stronger than ordinary magneto resistance. It was
soon realized that read heads incorporating GMR materials would be able to sense much smaller
magnetic fields, allowing the storage capacity of a hard disk to increase from 1 to 20 gigabits.
3.2 CONSTRUCTION OF GMR
The basic GMR device consists of a three-layer sandwich of a magnetic metal such as
cobalt with a nonmagnetic metal filling such as silver. Current passes through the layers
consisting of spin-up and spin-down electrons. 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. If the orientation of one of the magnetic layers can easily be changed by
the presence of a magnetic field then the device will act as a filter, or ‘spin valve’, letting through
more electrons when the spin orientations in the two layers are the same and fewer when
orientations are oppositely aligned. The electrical resistance of the device can therefore be
changed dramatically. In an ordinary electric Current, the spin points at random and plays no role
in determining the resistance of a wire or the amplification of a transistor circuit. Spintronic
devices, in contrast, rely on differences in the transport of “spin up” and “spin down” electrons.
When a current passes through the Ferro magnet, electrons of one spin direction tend to be
obstructed.
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