A brief introduction to giant magnetoresistance liu chang1, min wang1, lei liu1, siwei luo2, pan xiao1, 1hycorelle co. Classical theory of giant magnetoresistance in spin. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in multilayers composed of alternating ferromagnetic and nonmagnetic conductive layers. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and. The term giant magnetoresistance gm was coined to describe this effect. Giant magnetoresistance calculated from first principles volume 3 w. We ascribe this giant magnetoresistance to spindependent transmission of the conduction electrons between. Giant magnetoresistance simple english wikipedia, the free. Presence of influenza virus allows the binding of mnps to the gmr sensor and the binding is proportional to the concentration of. Conditions at which the conductivity variations associated with changes in the type of magnetization alignment in adjacent layers reach the values on the order of initial conductivity are considered.
Publishers pdf, also known as version of record includes final page. Giant magnetoresistance gmr is a very small magnetic effect found in thin layers of iron and other materials. The classical theory of transport is based on a statistical distribution function f that. Pdf giant magnetoresistance of 001fe001cr magnetic. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. Giant magnetoresistance and tunneling mag netoresistance arise when a magnetic field reorients the magnetization in different regions of a specimen causing a. Classical theory of giant magnetoresistance in spinvalve multilayers. Giant magnetoresistancebased biosensor for detection of.
If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple faq for additional information. This article is within the scope of wikiproject physics, a collaborative effort to improve the coverage of physics on wikipedia. Giant magnetoresistance and the spinvalve head of the giant magnetoresistance 6,7, was actually to build magnetic 2. Since the discovery of gmr the theoretical treatment of this effect became the subject. On the theory of giant magnetoresistance longitudinal.
The paper has been permanently removed due to issues. Giant magnetoresistance in magnetic multilayered systems the giant magnetoresistance effect is the change of electric conductivity in a system of metallic layers when an external magnetic field changes the magnetization of the ferromagnetic layers relative to each other. They demonstrated that the electric current in a magnetic multilayer consisting of a sequence of thin magnetic layers separated by equally thin nonmagnetic. A similar, though diminished effect was simultaneously discovered in fecrfe trilayers. A giant, reversible and nonvolatile electricfield manipulation of magnetoresistance to about 55% is realized at room temperature without the assistance of a magnetic field. Introduction giant magnetoresistance gmr is a device in which the resistance is change by the influence of magnetic field. With the discovery of giant magnetoresistance gmr, research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials andor artificial structures, which has lead to the idea of spintronics. Magnetic field sensors based on giant magnetoresistance gmr. Gmr is kind of like magnetoresistance on steroids, and was indeed a giant step for mankind when it was discovered in. The basic effect is that, using a special stack of layers alternating between ferromagnetic and not magnetic you can cause great variations on the electrical resistance of the material by applying a small magnetic field. Since this process is forbidden in classical physics, the tunnel. I have just modified 3 external links on giant magnetoresistance. Giant magnetoresistance simple english wikipedia, the. Theory of giant magnetoresistance effects in magnetic layered structures with antiferromagnetic coupling.
For a sphericallysymmetric energy spectrum therefore, the xxcomponent is field independent. Mid this article has been rated as midimportance on the. Giant magnetoresistance did not get its name by being a small effect. The term giant magnetoresistance gmr has come to be associated with certain thin metallic multi. Giant magnetoresistance of 001fe001cr magnetic superlattices.
Dec 30, 2012 with the discovery of giant magnetoresistance gmr, research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials andor artificial structures, which has lead to the idea of spintronics. In typical metal, at room temperature, orbital mr effects are very small, at most of the order of a few per cent. We are going to treat the magnetoresistance of metals in a quite general and simple manner. Magnetoresistance is a phenomenon in which the electrical resistivity of a material changes. Whats the explanation for the giant magnetoresistance effect. Giant magnetoresistance in magnetic multilayered systems. Macroscopic theory of giant magnetoresistance in magnetic. Pdf the 2007 nobel prize in physics was awarded to albert fert and peter grunberg for the discovery of giant magnetoresistance gmr. The giant magnetoresistance gmr is the large change in the electrical resistance which is induced by the application of a magnetic field to thin films composed of alternating ferromagnetic and nonmagnetic layers. The idea is to use magnetization changes to increase the sensitivity of the electrical current in the electronic. A brief introduction to giant magnetoresistance arxiv. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in thinfilm structures composed of alternating ferromagnetic and nonmagnetic conductive layers.
Anisotropic magnetoresistance before delving into the science of giant magnetoresis. If the insulating layer is thin enough typically a few nanometres, electrons can tunnel from one ferromagnet into the other. In thin metallic film systems, they observed that the magnetization of adjacent ferromagnetic films, separated by a thin nonmagnetic interlayer, spontaneously align parallel or. After establishing the theoretical f ramework for the description of the effect, and the constraints any material should have in order to show the effect, experimental work in wires, ribbons. All theories on the giant magnetoresistance effect developed thus far. Tightbinding theory of tunneling giant magnetoresistance j. There are a variety of effects that can be called magnetoresistance. Jun 17, 2016 the giant magnetoresistance gmr effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets.
H is the resistivity in the presence of a magnetic. The problem of conductivity of a multilayer sample alternating magnetic and nonmagnetic metal layers with a current parallel to its surfaces is solved using a set of kinetic equations. Magnetic field sensors based on giant magnetoresistance. Mathon department of mathematics, city university, london ec1v 0hb, united kingdom received 11 june 1997. Oct 09, 2007 the 2007 nobel prize in physics has been awarded to albert fert and peter grunberg for the discovery of giant magnetoresistance technology that is used to read data on hard disks. Giant nonvolatile manipulation of magnetoresistance in. Start this article has been rated as startclass on the projects quality scale. Giant magnetoresistance calculated from first principles. For a freeelectron gas, the rkky exchange integral for two atomic magnetic moments, embedded in a nonmagnetic host and being a distance r apart is. The giant magnetoresistance gmr material promises some important applications, which has many attractive features, for example. The 2007 nobel prize in physics was awarded to albert fert and peter grunberg for the discovery of gmr. Magnetoresistance is the tendency of a material often ferromagnetic to change the value of its electrical resistance in an externallyapplied magnetic field. The most spectacular was the discovery of antiferromagnetic exchange coupling between two fe films across a thin cr layer, and the subsequent discovery of giant magnetoresistance gmr in fecr multilayers and enhanced magnetoresistance in fecrfe trilayers also referred to as sandwich structures or spin valves.
The giant magnetoresistance effect is the change of electric. Discoverers of giant magnetoresistance used in hard drives. Giant magnetoresistance an overview sciencedirect topics. Giant magnetoresistance 2 magnetoresistance mr is the change of resistance of a conductor in an external magnetic field. The resistance of the multilayers was found to decrease by almost a factor of two when a field of 20 koe was applied at low temperatures 4. Gmr structure is thin film composed by alternating ferromagnetic f and nonmagnetic n layers. This change in resistance, in general a reduction, is related to the fieldinduced alignment of the magnetizations of the magnetic. The resistance change of a material induced by a magnetic field is called the magnetoresistive effect, which includes normal magnetoresistance omr, anisotropic magnetoresistance amr, giant magnetoresistance effect gmr, colossal magnetoresistance cmr. A brief introduction is given to gmr effects from scientific background to experimental observations and theoretical models. Tmr can be understood in terms of jullieres model, which is based on two assumptions.
Contact the authors the hku scholars hub has contact details for these authors. The giant magnetoresistance effect is the change of electric conductivity. Theory of the perpendicular magnetoresistance in magnetic multilayers. Giant magnetoresistance and applications sciencedirect. Macroscopic theory of giant magnetoresistance in magnetic granular metals. Giant magnetoresistance is a quantum mechanical magnetoresistance effect observed in thinfilm structures composed of alternating ferromagnetic and nonmagnetic conductive layers. The giant magnetoresistance gmr effect is a very basic phenomenon that occurs in magnetic materials ranging from nanoparticles over multilayered thin films to permanent magnets. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks. Tunneling magnetoresistance evgeny tsymbal nebraska.
Giant magnetoresistance of magnetic multilayers technische. Other articles where magnetoresistance is discussed. The standard spin valve shows about 56 % magnetoresistance. It is used to read and write information in hard drives the gmr effect can be measured when a magnet is used to change the flow of electricity. On the theory of giant magnetoresistance longitudinal current. We have developed a simple and sensitive method for the detection of influenza a virus based on giant magnetoresistance gmr biosensor. This assay employs monoclonal antibodies to viral nucleoprotein np in combination with magnetic nanoparticles mnps. Therefore, the sequential introduction of the magne. Mtjs with a 001oriented polycrystal textured mgo barrier. Tunneling magnetoresistance tmr is a dramatic change of the tunneling current in magnetic tunnel junctions when relative magnetizations of the two ferromagnetic layers change their alignment. Development of giant magnetoresistance material based on. Theory of giant magnetoresistance and tunneling magnetoresistance. The basic effect is that, using a special stack of layers alternating between ferromagnetic and not magnetic you can cause great variations on the electrical resistance of the material by applying a.
Giant magnetoresistance gmr is based on the physics of the magnetic tunnel junction discussed in relation to figs 9. As was shown later, high magnetoresistance values can also be obtained in other magnetic multilayers, such as cocu. Tunnel magnetoresistance tmr is a magnetoresistive effect that occurs in a magnetic tunnel junction mtj, which is a component consisting of two ferromagnets separated by a thin insulator. Other articles where giant magnetoresistance is discussed. Tunnel magnetoresistance effect and its applications. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance. Giant magnetoresistance is an outstanding example of the many ways in which research in fundamental science can produce surprisingly large advancements in industrial and consumer technology. First relying on induction coils, later versions of hard disk drives capitalized on new technologies and knowledge, incorporating anisotropic magnetoresistance amr, or mr and, a few years later, giant magnetoresistance gmr. Although the term giant in giant magnetoresistance gmr seems incongruous for a nanotechnology device, it refers to a large change in resistance typically 10 to 20% when the devices are subjected to a magnetic field, compared with a maximum sensitivity of a few percent for other types of magnetic sensors. Tightbinding theory of tunneling giant magnetoresistance.
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