Spin Electrons and Its Use with Computers - Research Paper Example

Spintronics Introduction Spin electrons, or spintronics refers to the study f the role played by electron spin in semiconductor world as well as possible devices that utilize spin properties other than charge degrees of freedom. World computers could be revolutionized by a new set of materials that convey data based on an electron’s spin. Magnetic elements such as cobalt have been added in some oxides which are non-magnetic to make them ferromagnetic1. Researchers and scientists around the world have for the first time that magnetism in such materials directly depends on the presence of dopants that make semiconductors out of insulators. An example of such a material is zinc oxide in which cobalt replaces some of the zinc atoms. Spintronics incorporates new discoveries in semiconductor world to bring changes in the electronic makeup and powering of computers. The spin transport and spin relaxation phenomena in metals and semiconductors will soon be used by devices to replace current electrical technology. The technology aims at developing faster circuits that operate on heat and magnetic energy rather than conventional electricity. This topic is critical because, without a revolutionary approach such as, spintronics, the computer industry will soon face a lot of challenges concerning processor speed. Cobalt-doped zinc diode, or such like materials, could be fundamental in manufacturing of computer chips for spintronics to be realized. With this new innovatory approach, circuits will use the electron spin instead of electron charge to carry signals and process information. For such chips to be developed, semiconductors that cannot lose magnetism at or above room temperature must be found. With this phenomenon, the electron’s spin that the signal is embedded on is preferentially unidirectional. Other such solid-state materials are already in existence, but they fail to maintain their crucial magnetic properties at room temperature, thus limiting their importance. Almost everything ranging from scientific discoveries to consumer electronics is affected by advances in computer technologies. For instance, further discoveries in science depend on ever fast computers to perform computations that can’t be done now. Researchers could avoid many challenges in their work if computers that are based on spintronics could be economically developed. This paper is going to look at three main points in spintronics. The first point is about transistors and the heat they generate. It’s quite clear that today’s technology for making high speed computer processors involves reducing the size of transistors so that many of them can be easily packed together onto a single computer chip. However, the manufacturers are facing a big challenge from this very large scale integration of transistors because mounting too many of them on one chip can melt the chip as a result of too much heat they generate which cannot dissipate fast enough. Today, a transistor is a minute but very important component of a computer that is used to switch on and off the flow of electrons. The troublesome heat arises as a result of the flow of electrons against the resistance of the nearby materials. But computers can’t work without transistors. They depend on transistor’s states of ‘on’ and ‘off’ to convey the digital logic that computers use to enable them perform their functions2. Computer logic just uses the binary system of zeros and ones, which is how a computer selects the off or on options in a transistors electron flow. So, spintronics technology is trying to come up with a new and more fast and efficient way of providing the zeros and ones that a computer need in data processing. Other than having electrons flow hotly through a transistor, researchers are trying to design new types of materials that will allow the electrons to be ‘cool’ by only spinning in one of two opposite ways. As far as quantum mechanics is concerned, an electron is allowed by nature only either to spin down or to spin up (to be discussed in detail in point three) when a magnetic field is present. A computer chip that could incorporate these two new choices presented by spintronics could open the door for the entire new era of low-power consuming super-fast computers. Scientists and researchers have in the recent years discovered that an orientation of an electron’s spin can be changed by merely using a voltage. Integrating these interesting new spintronics transistors into a computer chip is one of the goals of a new research effort, C-SPIN, based at the University of Minnesota3. This effort was recently funded by the Semiconductor Corporation and the U.S. Defense Advanced Research Projects Agency. Nitin Samarth, a professor of physics from Penn state together with his research team is trying to develop new spintronics materials that could facilitate electrons’ spin inside a computer. Samarth and his team are also determining the electron spin propagation in new types of solid-state devices and utilizing Penn State’s nanofabrication facility to develop sub-micron scale equipment. These highly specialized devices they are creating might function as spintronics transistors. The second point is about a hybrid technology referred to as thermo-spintronics. This is a technology that would convert heat to electron spin. This conversion would serve as a solution two problems within the computing industry. It will enable dissipation of waste heat and also improve computer power and speed without creating more heat. Spintronics is anticipated to produce better results for new computers because the phenomenon is claimed to produce no heat. According to researchers, the present day computers could be working at higher speeds than they do, but can’t do so because if they did they will melt within a very short time due to heat. Therefore thermal management within the semiconductor industry requires a lot of money. In one possible application of thermo-spintronics a device could be mounted on a conventional microprocessor to drain off waste heat away to run computation or additional memory. Unfortunately, such applications are still a long way off. Researchers at University of California conducted a study to determine how heat can be converted to spin in semiconductors. They used gallium manganese arsenide. Gallium arsenide is used in cell phones today and it was realized that with the addition of manganese, the semiconductor is endowed with magnetic properties4. The researchers carefully prepared the samples of this material into thin single-crystal films. The samples were then processed for the experiment. The spins of the charges in this kind of material line up parallel with the orientation of the overall magnetic field of the sample. So in the effort to detect the electron’s spin, the researchers were trying to find out whether the electrons in any specific area of the material were aligned as spin-down or spin-up. The researchers, also to their own surprise realized that two pieces of the material need not be physically interlinked for the effect to transmit from one to the other. They were able to realize from their experiments that the electrons were aligned in the spin-up direction on the hot side and spin down direction on the cool side. Then two pieces of the material separated by a gap were created. If electrical conductivity caused the spin effect, then the gap would hinder the effect from spreading4. It was discovered that each piece would have unique distribution of spin-down and spin-up electrons. To some extent, the effect crossed the gap as there was a spin-up on side of the first piece and a spin-down on the far side of the second piece. The last point is an emphasis of the two possible states of an electron spin: spin up or spin down. The passage of ‘up’ and ‘down’ electrons are differently affected by the presence of a magnetic field. With all conditions stable and normal, the conducting electrons’ spin are usually half up and half down. Substantial and surprising changes in spin properties can be realized through control of spin electrons within a device. A modern generation of gadgets centered on spin manipulation and control in solids may bring with it new functionality that could be a base for absolutely new computational archetypes4. For instance, the Giant Magneto-resistive (GMR) spin-valve head for magnetic hard disk drives, a first extensively used spintronic device, experiences large changes in electrical resistance as a result of differences in the relative magnetic orientation of layers on each side of a layer merely 2 to 4 atoms thick. When the spin alignments are parallel and in the same direction, electrons with one type of spin experience great resistance while those with the opposite spin pass freely. When the magnetic alignments are anti-parallel, i.e. are in opposite directions, all the electrons experience resistance, leading to a high overall electrical resistance within the head. There are two different approaches that are currently being used in the effort to design and manufacture spintronic structures. The first approach is working on the existing GMR-based technology to perfect it by either making variations in the existing devices to enhance better spin filtering or developing new materials with higher electrons’ spin polarization. The second approach is more crucial and centers on finding better ways of both generation as well as utilization of spin-polarized currents. This approach is vital because it lies in the fact that no signal amplification is done by existing metal-based devices, whereas solid-state based spintronic devices could amplify signals and serve as multi-functional devices in general4. In addition to that, it would be much easier to merge traditional semiconductor technology with semiconductor-based devices. While there are clear benefits of integrating spintronic application with conventional semiconductors, many basic questions regarding the integration of semiconductors with other material to come up with novel spintronic technology remain unanswered. For instance, whether putting a semiconductor material in contact with another material would hinder transport across the boundary or not. In the old days, people tried acquaint themselves with knowledge on spin transport in hybrid semiconductor devices by borrowing knowledge from conventional studies of magnetic materials. Nonetheless, there is another option involving the direct study of spin transport in all semiconductors. In such circumstances, integration of material inhomogeneities and optical manipulation could be used to spin transport properties5. In addition to research on various spin transistors as well as spin transport properties of semiconductor materials, an ambitious and long-term spintronics phenomenon is the application of nuclear and electron spins to quantum computation and quantum information processing. Many scientists have for a long period of time argued that quantum mechanics is superior over classical physics as far as physical computation is concerned. However, the introduction of quantum error correction schemes and Shor’s factorization algorithm are the ones that gave physical computation a major boost. Magnetic RAM also known as MRAM is another very important spintronic device. Unlike traditional RAMs, MRAMs will still retain stored information even when the power goes off. The personal computers of this generation utilize DRAM and SRAM which are both volatile memories that lose informed once power is turned off. MRAM is manufactured based on the principle of magnetic tunneling junction (MTJ)5. MTJ is a device that consists of three layers: two ferromagnetic layers and a thin insulating layer between them. Instead of storing bits as electric charges, MRAMs store them as magnetic polarities. It holds 1 when its polarity points in one direction and hold 0 when its polarity points in other direction. These bits require electricity to change but not to maintain them making MRAMs non-volatile. Conclusion Spintronic transistors built by researchers are now being used to align the electron’s magnetic spins in computer chips at room temperature. The phenomenon is a step toward computers and other spintronic devices that use less energy and are faster than their electronic counterparts. Spintronics can give much better results that today’s magneto-electronics that are based on Ferro-magnetic metal layers as it does not produce any heat. In contrast to electronic circuits, it intends to modify magnetic properties through the carrier density to develop new spintronic devices. It involves research of conventional magnetism, solid state physics as well as quantum computation. Many people view spintronics as just a way of getting more information from an electron, but it’s really about moving to more advanced generation of electronics. Many problems facing computer today could be solved by using spintronics. Bibliography Shinjō, Teruya. 2009. Nanomagnetism and spintronics. Amsterdam: Elsevier. http://www.myilibrary.com?id=228588. Manipatruni Sasikanth, Nikonov Dmitri and Young Ian. Circuit Theory for SPICE of Spintronic Integrated Circuits. Retrieved on 19/04/14 from Arxiv.org Mukesh D. Patil, Jitendra S. Pingale, & Umar I. Masumdar. 2013. Overview of Spintronics. International Journal of Engineering Research & Technology. 2(6) Gray, Nathan W., and Ashutosh Tiwari. 2011. "Room temperature electrical injection and detection of spin polarized carriers in silicon using MgO tunnel barrier". Applied Physics Letters. 98 (10): 102112. Awschalom, D., D. Loss, and N. Samarth. 2002. Semiconductor spintronics and quantum computation. Berlin: Springer. Read More