Spintronics



Spintronics

1. Introduction:

Conventional electronic devices rely on the transport of electrical charge carriers –electrons in a semiconductor such as silicon. Now, however, physicists are trying to exploit the ‘spin’ of the electron rather than its charge to create a remarkable new generation of ‘spintronic’ devices which will be smaller, more versatile and more robust than those currently making up silicon chips and circuit elements.

Imagine a data storage device of the size of an atom working at a speed of light. Imagine a computer memory thousands of times denser and faster than today’s memories and also imagine a scanner technique which can detect cancer cells even though they are less in number. The above-mentioned things can be made possible with the help of an exploding science – “Spintronics”.

Spintronics is a 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 dimensions of an electron other than its charge and mass i.e. spin. 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 technology.

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 physicists are 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 form the foundations of spintronics.

Information-processing technology has thus far relied on purely charge based devices ranging from the now quantum, vacuum 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.

2. Basic Principle:

The basic principle involved is the usage of spin of the electron in addition to mass and charge of electron. Electrons like all fundamental particles have a property called spin which can be orientated in one direction or the other – called ‘spin-up’ or ‘spin-down’ –like a top spinning anticlockwise or clockwise. Spin is the root cause of magnetism and is a kind of intrinsic angular momentum that a particle cannot gain or lose. The two possible spin states naturally represent ‘0’and ‘1’in logical operations. Spin is the characteristics that makes the electron a tiny magnet complete with north and south poles .The orientation of the tiny magnet ‘s north-south poles depends on the particle’s axis of spin.

Fundamentals of spin:

1. In addition to their mass, 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

. [pic]

Fig.1. Electron spinning

3. Scientists represent the spin with a vector. For a sphere spinning “west to east”, the vector points “north” or “up”. It points “south” or “down” for the spin from “east to west”.

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 flow.

6. Spintronic devices create spin-polarized currents and use the spin to control current flow.

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 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 spin-down electrons.

3. Giant Magneto Resistance:

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 send it to the various succeeding circuits.

The effect is observed as a significant change in the electrical resistance depending on whether the magnetization of adjacent ferromagnetic layers are in a parallel or anantiparallel alignment. The overall resistance is relatively low for parallel alignment and relatively high for antiparallel alignment.

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” (GMR). GMR is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and non magnetic layers. The 2007 Nobel Prize in physics was awarded to Albert Fert and Peter Grünberg for the discovery of GMR.

Giant magnetoresistance (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 magnetoresistance. 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.

3.1 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.

A ferromagnet 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 antiparallel 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 antiparallel 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.

GMR has triggered the rise of a new field of electronics called spintronics which has been used extensively in the read heads of modern hard drives and magnetic sensors. A hard disk storing binary information can use the difference in resistance between parallel and antiparallel layer alignments as a method of storing 1s and 0s.

A high GMR is preferred for optimal data storage density. Current perpendicular-to-plane (CPP) Spin valve GMR currently yields the highest GMR. Research continues with older current-in-plane configuration and in the tunnelling magnetoresistance (TMR) spin valves which enable disk drive densities exceeding 1 Terabyte per square inch.

Hard disk drive manufacturers have investigated magnetic sensors based on the colossal magnetoresistance effect (CMR) and the giant planar Hall effect. In the lab, such sensors have demonstrated sensitivity which is orders of magnitude stronger than GMR. In principle, this could lead to orders of magnitude improvement in hard drive data density. As of 2003, only GMR has been exploited in commercial disk read-and-write heads because researchers have not demonstrated the CMR or giant planar hall effects at temperatures above 150K.

Magnetocoupler is a device that uses giant magnetoresistance (GMR) to couple two electrical circuits galvanicly isolated and works from AC down to DC.

Vibration measurement in MEMS systems.

Detecting DNA or protein binding to capture molecules in a surface layer by measuring the stray field from superparamagnetic label particles.

4. Spintronic Devices:

Spintronic devices are those devices which use the Spintronic technology. Spintronic-devices combine the advantages of magnetic materials and semiconductors. They are expected to be non-volatile, versatile, fast and capable of simultaneous data storage and processing, while at the same time consuming less energy. Spintronic-devices are playing an increasingly significant role in high-density data storage, microelectronics, sensors, quantum computing and bio-medical applications, etc.

Some of the Spintronic devices are

• Magnetoresistive Random Access Memory(MRAM)

• Spin Transistor

• Quantum Computer

• Spintronic Scanner

4.1 MRAM (Magnetoresistive Random access Memory)

An important spintronic device, which is supposed to be one of the first spintronic devices that have been invented, is MRAM.

Unlike conventional random-access, MRAMs do not lose stored information once the power is turned off...A MRAM computer uses power, the four page e mail will be right there for you. Today pc use SRAM and DRAM both known as volatile memory. They can store information only if we have power. DRAM is a series of

Capacitors, a charged capacitor represents 1 where as an uncharged capacitor represents 0. To retain 1 you must constantly feed the capacitor with power because the charge you put into the capacitor is constantly leaking out.

MRAM is based on integration of magnetic tunnel junction (MJT). Magnetic tunnel junction is a three-layered device having a thin insulating layer between two metallic ferromagnets. Current flows through the device by the process of quantum tunneling; a small number of electrons manage to jump through the barrier even though they are forbidden to be in the insulator. The tunneling current is obstructed when the two ferromagnetic layers have opposite orientations and is allowed when their orientations are the same. MRAM stores bits as magnetic polarities rather than electric charges. When a big polarity points in one direction it holds1, when its polarity points in other direction it holds 0. These bits need electricity to change the direction but not to maintain them. MRAM is non volatile so, when you turn your computer off all the bits retain their 1`s and 0`s.

4.2 Spin Transistor

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 1 before they reach the collector due to the spin-orbit coupling effect.

[pic]

Fig. 2 Spin polarized field effect transistor.

Vg is the gate voltage. When Vg is zero the injected spins which are transmitted through the 2DEG layer starts processing before they reach the collector, thereby reducing the net spin polarization. Vg is the gate voltage. When Vg >> 0 the precession of the electrons is controlled with electric filed thereby allowing the spins to reach at the collector with the same polarization.

Hence the net spin polarization is reduced. In order to solve this problem an electric field is applied perpendicularly to the plane of the film by depositing a gate electrode on the top to reduce the spin-orbit coupling effect as illustrated in Figure 4. By controlling the gate voltage and polarity can the current in the collector can be modulated there by mimicking the MOSFET of the conventional electronics. Here again the problem of conductivity mismatch between the source and the transmitting layer is an important issue. The interesting thing would be if a Heusler alloy is used as the spin source and a semimetallic Heusler alloy as the transmitting layer, the problem of conductivity mismatch may be solved. For example from the Slater-Pauling curve Mt = Zt - 24, Heusler alloys with Mt >>0 can act as spin sources and alloys with Mt ~ 0 can act as semimetals. Since both the constituents are of same structure the possibility of conductivity mismatch may be less.

Traditional transistors use on-and-off charge currents to create bits—the binary zeroes and ones of computer information. “Quantum spin field effect” transistor will use up-and-down spin states to generate the same binary data. One can think of electron spin as an arrow; it can point upward or downward; “spin-up and spin-down can be thought of as a digital system, representing the binary 0 and 1. The quantum transistor employs also called “spin-flip” mechanism to flip an up-spin to a downspin, or change the binary state from 0 to 1.

One proposed design of a spin FET (spintronic field-effect transistor) has a source and a drain, separated by a narrow semi conducting channel, the same as in a conventional FET.

In the spin FET, both the source and the drain are ferromagnetic. The source sends spin-polarized electrons in to the channel, and this spin current flow easily if it reaches the drain unaltered (top). A voltage applied to the gate electrode produces an electric field in the channel, which causes the spins of fast-moving electrons to process, or rotate (bottom). The drain impedes the spin current according to how far the spins have been rotated. Flipping spins in this way takes much less energy and is much faster than the conventional FET process of pushing charges out of the channel with a larger electric filed.

One advantage over regular transistors is that these spin states can be detected and altered without necessarily requiring the application of an electric current. This allows for detection hardware that are much smaller but even more sensitive than today's devices, which rely on noisy amplifiers to detect the minute charges used on today's data storage devices. The potential end result is devices that can store more data in less space and consume less power, using less costly materials. The increased sensitivity of spin transistors is also being researched in creating more sensitive automotive sensors, a move being encouraged by a push for more environmentally-friendly vehicles

A second advantage of a spin transistor is that the spin of an electron is semi-permanent and can be used as means of creating cost-effective non volatile solid state storage that does not require the constant application of current to sustain. It is one of the technologies being explored for Magnetic Random Access Memory (MRAM)

Spin transistors are often used in computers for data processing. They can also be used to produce a computer's random access memory and are being tested for use in magnetic RAM. This memory is superfast and information stored on it is held in place after the computer is powered off, much like a hard disk.

|Electronic Devices |Spintronic devices |

|1. Based on properties of charge of the electron |1. Based on intrinsic property spin of electron |

|2. Classical property |2. Quantum property |

|3. Controlled by an external electric field in modern electronics |3. Controlled by external magnetic field |

|4. Materials: conductors and semiconductors |4.Materials: ferromagnetic materials |

|5. Based on the number of charges and their energy |5. Two basic spin states; spin-up and spin-down |

|6. Speed is limited and power dissipation is high |6. Based on direction of spin and spin coupling, high speed |

4.3 Quantum Computer:

A quantum computer is a device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from traditional computers based on transistors. The basic principle behind quantum computation is that quantum properties can be used to represent data and perform operations on these data. A theoretical model is the quantum Turing machine, also known as the universal quantum computer.

Although quantum computing is still in its infancy, experiments have been carried out in which quantum computational operations were executed on a very small number of qubits (quantum bits). Both practical and theoretical research continues, and many national government and military funding agencies support quantum computing research to develop quantum computers for both civilian and national security purposes, such as cryptanalysis.

If large-scale quantum computers can be built, they will be able to solve certain problems much faster than any current classical computers. All problems solvable with a quantum computer can also be solved using a traditional computer given enough time and resources.

In a quantum computer, the fundamental unit of information (called a quantum bit or qubit), is not binary but rather more quaternary in name. This qubit property arises as a direct consequence of its adherence to the laws of quantum mechanics. A qubit can exist not only in a state corresponding to the logical state 0 or 1 as in a classical bit, but also in states corresponding to a blend or superposition of these classical states. In other words, a qubit can exist as a zero, a one or simultaneously as both 0 and 1, with a numerical coefficient representing the probability for each state.

Each electron spin can represent a bit; for instance, a 1 for spin up and 0 for spin down. With conventional computers, engineers go to great lengths to ensure that bits remain in stable, well-defined states. A quantum computer, in contrast, lies on encoding information within quantum bits, or qubits, each of which can exist in a superposition of 0 and 1. By having a large number of qubits in superposition of alternative states, a quantum computer intrinsically contains a massive parallelism. Unfortunately, in most physical systems, interactions with the surrounding environment rapidly disrupt these superposition states. A typical disruption would effectively change a superposition of 0 and 1 randomly into either a 0 or a 1, as process called decoherence. State-of-the-art qubits based on the charge of electrons in a semiconductor remain coherent for a few picoseconds at best and only at temperatures too low for practical applications. The rapid decoherence occurs because the electric force between charges is strong and long range.

In traditional semiconductor devices, this strong interaction is beneficial, permitting delicate control of current flow with small electronic fields. To quantum coherent devices, however, it is disadvantage.

As a result, an experiment was conducted on the qubits, which are based on the electron-spin. Electron-spin qubits interact only weakly with the environment surrounding them, principally through magnetic fields that are non-uniform in space or changing in time. Such fields can be effectively shielded. The goal of the experiment was to create some of these coherent spin states in a semiconductor to see how long they could survive. Much to the surprise, the optically excited spin states in ZnSe remained coherent for several nanoseconds at low temperatures—1,000 times as long as charge-based qubits. The states even survived for a few nanoseconds at room temperature. Subsequent studies of electrons in gallium arsenide (GaAs) have shown that, under optimal conditions, spin coherence in a semiconductor is possible.

Spintronic Qubits

1. In a conventional computer every bit has a definite value of 0 or 1. A series of eight bits can represent any number from 0 to 255, but only one number at a time.

2. Electron spins restricted to spin up and spin down could be used as bits.

3. Quantum bits, or qubits, can also exist as super positions of 0 and 1, in effect being both numbers at once. Eight qubits can represent every number from 0 to 255 simultaneously.

4. Electron spins are natural qubits; tilted electrons is a coherent superposition of spin up and spin down and is less fragile than other quantum electronic states.

5. Qubits are extremely delicate: stray interactions with their surroundings degrade the superposition extremely quickly, typically converting them in to random ordinary bits.

While a classical three-bit state and a quantum three-qubit state are both eight-dimensional vectors, they are manipulated quite differently for classical or quantum computation. For computing in either case, the system must be initialized, for example into the all-zeros string,[pic] corresponding to the vector (1, 0, 0,0,0,0, 0, and 0). In classical randomized computation, the system evolves according to the application of stochastic matrices, which preserve that the probabilities add up to one (i.e., preserve the L1 norm). In quantum computation, on the other hand, allowed operations are unitary matrices, which are effectively rotations (they preserve that the sums of the squares add up to one, the Euclidean or L2 norm). (Exactly what unitaries can be applied depend on the physics of the quantum device.) Consequently, since rotations can be undone by rotating backward, quantum computations are reversible. (Technically, quantum operations can be probabilistic combinations of unitaries, so quantum computation really does generalize classical computation. See quantum circuit for a more precise formulation.)

Finally, upon termination of the algorithm, the result needs to be read off. In the case of a classical computer, we sample from the probability distribution on the three-bit register to obtain one definite three-bit string, say 000. Quantum mechanically, we measure the three-qubit state, which is equivalent to collapsing the quantum state down to a classical distribution (with the coefficients in the classical state being the squared magnitudes of the coefficients for the quantum state, as described above) followed by sampling from that distribution. Note that this destroys the original quantum state. Many algorithms will only give the correct answer with a certain probability; however by repeatedly initializing, running and measuring the quantum computer, the probability of getting the correct answer can be increased.

4.4 Spintronic Scanner

Cancer cells are the somatic cells which are grown into abnormal size. The Cancer

cells have different electromagnetic sample when compared to normal cells. For many types of Cancer, it is easier to treat and cure the Cancer if it is found early. There are many different types of Cancer, but most Cancers begin with abnormal cells growing out of control, forming a lump that's called a tumor. The tumor can continue to grow until the Cancer begins to spread to other parts of the body. If the tumor is found when it is still very small, curing the Cancer can be easy. However, the longer the tumor goes unnoticed, the greater the chance that the Cancer has spread. This makes treatment more difficult. Tumor developed in human body, is removed by performing a surgery. Even if a single cell is present after the surgery, it would again develop into a tumor. In order to prevent this, an efficient route for detecting the Cancer cells is required. Here, in this paper, we introduce a new route for detecting the Cancer cells after a surgery. This accurate detection of the existence of Cancer cells at the beginning stage itself entertains the prevention of further development of the tumor.

This spintronic scanning technique is an efficient technique to detect cancer cells even when they are less in number.

An innovative approach to detect the cancer cells with the help of Spintronics:

The following setup is used for the detection of cancer cells in a human body:

(a)Polarized electron source

(b) Spin detector

(c)Magnetic Field

4.4.1Polarized electron source:

A beam of electrons is said to be polarized if their spins point, on average, in a specific direction. There are several ways to employ spin on electrons and to control them. The requirement for this paper is an electron beam with all its electrons polarized in a specific direction. The following are the ways to meet the above said requirement: Photoemission from negative electron affinity GaAs Chemi-ionization of optically pumped meta stable Helium An optically pumped electron spin filter A Wein style injector in the electron source A spin filter is more efficient electron polarizer which uses an ordinary electron source along with a gaseous layer of Rb. Free electrons diffuse under the action of an electric field through Rb vapour that has been spin polarized in optical pumping. Through spin exchange collisions with the Rb, the free electrons become polarized and are extracted to form a beam. To reduce the emission of depolarizing radiation, N2 is used to quench the excited Rb atoms during the optical pumping cycle.

4.4.2 Spin detectors:

There are many ways by which the spin of the electrons can be detected efficiently. The spin polarization of the electron beam can be analyzed by using: 

(a)Mott polarimeter 

(b)Compton polarimeter

(c)Moller type polarimeter

Typical Mott polarimeters require electron energies of ~100 kV. But Mini Mott polarimeter uses energies of ~25 keV, requiring a smaller overall design. The Mini Mott polarimeter has three major sections: the electron transport system, the target chamber, and the detectors. The first section the electrons enter is the transport system. An Einsel lens configuration was used here. Two sets of four deflectors were used as the first and last lens. The electrons next enter the target chamber. The chamber consists of a cylindrical target within a polished stainless steel hemisphere. A common material used for the high-Z nuclei target is gold. Low-Z nuclei help minimize unwanted scattering, so aluminum was chosen. Scattered electrons then exit the target chamber and are collected in the detectors. Thus there are many methods for detecting the spin polarization of electrons. 

4.4.3 External Magnetic Field:

An external magnetic field is required during this experiment. The magnetic field is applied after the surgery has undergone. First, it is applied to an unaffected part of the body and then to the surgery undergone part of the body. It is already mentioned that the magnetic field could easily alter the polarization of electrons. 

This technique using spintronics is suggested by us to identify tumor cells after surgery.

The procedure for doing this experiment is as follows:

Optical Spin Filter:

After surgery and the removal of the tumor, the patient is exposed to a strong magnetic field. Now the polarized electron beam is applied over the unaffected part and spin orientation of electrons are determined using polarimeter. Then the same polarized beam is targeted over the affected part of the body and from the reflected beam, change in spin is determined. Based on these two values of spin orientation, the presence of tumor cells can be detected even if they are very few in number. Hence, we suggest this method for the detection purpose. A detailed view of this innovative approach is given as follows. 

Spin Orientation of the unaffected part of the body:

Applying Magnetic Field:

When the magnetic field is applied to the unaffected part of the human body, the normal somatic cells absorbs the magnetic energy and retains it. 

Determinig the Spin orientation:

When the electrons get incident on the cells the magnetic energy absorbed by the cells alters the spin orientation of the electrons. These electrons get reflected and it is detected by the Mott polarimeter. Then the change in spin orientation of the electrons is measured as Sx. 

Spin Orientation of the surgery undergone part of the body:

Applying Magnetic Filter:

In the surgery undergone part of the body an external magnetic field is applied. The cancer cells which are present, if any, will absorb more magnetic energy than the normal cells since they differ in their electromagnetic pattern. 

Determinig the spin Orientation:

Now an electron beam which is polarized is incident on the surgery undergone part of the body. The magnetic energy absorbed by the cancer cell alter the spin orientation of the electron beam. Since cancer cells absorb more magnetic energy, the change in orientation caused by them is also more. If no cancer cells are present the amount of change is equal to the previous case. The change in spin is measured by the polarimeter as Sy.

Inference:

If the change in the spin in the unaffected part of the body is same as that of the surgery undergone part, i.e.

If Sx=Sy

Then,

There are no cancer cells in the surgery undergone part of the body and all the cells have

been removed by the surgery.

If the change in spin in the unaffected part is not equal to the change caused by the surgery undergone part of the body, i.e.

If Sx not equals Sy

Then,

There are some cancer cells in the surgery undergone part of the body and the cancer cells are not completely removed by the surgery.

The steps involved are:

1) The patient is exposed to a strong magnetic field so that his body cell gets magnetized.

2) A beam of electrons with polarized spin is introduced on the unaffected part of the body and the change in spin is detected by a polarimeter. Let it be X

3) A beam of electrons with polarized spin is introduced on the part which had undergone surgery. And the corresponding change in spin be Y

4)If X - Y = 0, it indicates that cancer cells have been removed from the body, if not it indicates the presence of traces of cancer cells and it has to be treated again for ensuring complete safety to the patient 

Thus this technique efficiently identifies the presence of cancer cells in that part of the body that has undergone surgery to prevent any further development. 

5. Conclusion:

So with this paper we have proved that the new generation of computing and information technology is on its way to revolutionize the 21st century. We believe it makes sense instead to build on the extensive foundations of conventional electronic semiconductor technology; we exploit the spin of the electron and create new devices and circuits, which could be more beneficial. Spintronics, which depend on the spin of the electron, has a great potential of spinning this global village into an unexpected digital atomic world which has a capability of manipulating at atomic level. This would make things smaller and cheaper and more affordable by a common man. What ever may be the discovery or invention made will have its worth forever only if it finds its use in common man’s life. We wish and hope spintroincs will have it’s into common man’s life.

-----------------------

InGaAs

InAlAs

gate

Collector

Source

Vgg

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download