The idea is to use magnetization changes to increase the sensitivity of the electrical current in the electronic. The 2007 nobel prize in physics was awarded to albert fert and peter grunberg for the discovery of gmr. 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. 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. 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. This assay employs monoclonal antibodies to viral nucleoprotein np in combination with magnetic nanoparticles mnps. Mid this article has been rated as midimportance on the.
Theory of giant magnetoresistance effects in magnetic layered structures with antiferromagnetic coupling. Development of giant magnetoresistance material based on. Magnetoresistance is a phenomenon in which the electrical resistivity of a material changes. We have developed a simple and sensitive method for the detection of influenza a virus based on giant magnetoresistance gmr biosensor. Tunneling magnetoresistance evgeny tsymbal nebraska. The giant magnetoresistance gmr material promises some important applications, which has many attractive features, for example. This article is within the scope of wikiproject physics, a collaborative effort to improve the coverage of physics on wikipedia. Macroscopic theory of giant magnetoresistance in magnetic. Pdf giant magnetoresistance of 001fe001cr magnetic.
Tightbinding theory of tunneling giant magnetoresistance j. 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. Giant magnetoresistance of magnetic multilayers technische. Tightbinding theory of tunneling giant magnetoresistance. 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. Tmr can be understood in terms of jullieres model, which is based on two assumptions. 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.
A brief introduction is given to gmr effects from scientific background to experimental observations and theoretical models. Theory of giant magnetoresistance and tunneling magnetoresistance. Mathon department of mathematics, city university, london ec1v 0hb, united kingdom received 11 june 1997. 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 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. Giant magnetoresistance is a quantum mechanical magnetoresistance effect observed in thinfilm structures composed of alternating ferromagnetic and nonmagnetic conductive layers. Classical theory of giant magnetoresistance in spin. This change in resistance, in general a reduction, is related to the fieldinduced alignment of the magnetizations of the magnetic. Anisotropic magnetoresistance before delving into the science of giant magnetoresis.
Giant nonvolatile manipulation of magnetoresistance in. Macroscopic theory of giant magnetoresistance in magnetic granular metals. Giant magnetoresistance 2 magnetoresistance mr is the change of resistance of a conductor in an external magnetic field. Giant magnetoresistance calculated from first principles. Giant magnetoresistance and tunneling mag netoresistance arise when a magnetic field reorients the magnetization in different regions of a specimen causing a. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance. Giant magnetoresistance gmr is a very small magnetic effect found in thin layers of iron and other materials.
Jan 16, 2019 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. Publishers pdf, also known as version of record includes final page. A brief introduction to giant magnetoresistance arxiv. I have just modified 3 external links on giant magnetoresistance. Magnetic field sensors based on giant magnetoresistance gmr. The standard spin valve shows about 56 % magnetoresistance. 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. Since the discovery of gmr the theoretical treatment of this effect became the subject.
Since this process is forbidden in classical physics, the tunnel. 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. A brief introduction to giant magnetoresistance liu chang1, min wang1, lei liu1, siwei luo2, pan xiao1, 1hycorelle co. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. All theories on the giant magnetoresistance effect developed thus far. Giant magnetoresistancebased biosensor for detection of. Giant magnetoresistance an overview sciencedirect topics. Classical theory of giant magnetoresistance in spinvalve multilayers. The giant magnetoresistance effect is the change of electric. Tunnel magnetoresistance effect and its applications. Magnetic field sensors based on giant magnetoresistance.
Other articles where giant magnetoresistance is discussed. Giant magnetoresistance in magnetic multilayered systems. 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. The term giant magnetoresistance gm was coined to describe this effect. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in thinfilm structures composed of alternating ferromagnetic and nonmagnetic conductive layers. Pdf the 2007 nobel prize in physics was awarded to albert fert and peter grunberg for the discovery of giant magnetoresistance gmr. Theory of the perpendicular magnetoresistance in magnetic multilayers. We ascribe this giant magnetoresistance to spindependent transmission of the conduction electrons between. H is the resistivity in the presence of a magnetic. On the theory of giant magnetoresistance longitudinal current. In thin metallic film systems, they observed that the magnetization of adjacent ferromagnetic films, separated by a thin nonmagnetic interlayer, spontaneously align parallel or. A giant, reversible and nonvolatile electricfield manipulation of magnetoresistance to about 55% is realized at room temperature without the assistance of a magnetic field. 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.
As was shown later, high magnetoresistance values can also be obtained in other magnetic multilayers, such as cocu. 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. In typical metal, at room temperature, orbital mr effects are very small, at most of the order of a few per cent. 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. 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.
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. Discoverers of giant magnetoresistance used in hard drives. Giant magnetoresistance calculated from first principles volume 3 w. If the insulating layer is thin enough typically a few nanometres, electrons can tunnel from one ferromagnet into the other. 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 simple english wikipedia, the.
Presence of influenza virus allows the binding of mnps to the gmr sensor and the binding is proportional to the concentration of. Contact the authors the hku scholars hub has contact details for these authors. Gmr is kind of like magnetoresistance on steroids, and was indeed a giant step for mankind when it was discovered in. For a sphericallysymmetric energy spectrum therefore, the xxcomponent is field independent. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks. Giant magnetoresistance simple english wikipedia, the free. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and. Giant magnetoresistance gmr is based on the physics of the magnetic tunnel junction discussed in relation to figs 9. Giant magnetoresistance of 001fe001cr magnetic superlattices.
A similar, though diminished effect was simultaneously discovered in fecrfe trilayers. Gmr structure is thin film composed by alternating ferromagnetic f and nonmagnetic n layers. Magnetoresistance is the tendency of a material often ferromagnetic to change the value of its electrical resistance in an externallyapplied magnetic field. 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. Mtjs with a 001oriented polycrystal textured mgo barrier. Therefore, the sequential introduction of the magne. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in multilayers composed of alternating ferromagnetic and nonmagnetic conductive layers. The classical theory of transport is based on a statistical distribution function f that. On the theory of giant magnetoresistance longitudinal. The paper has been permanently removed due to issues. The giant magnetoresistance effect is the change of electric conductivity. Giant magnetoresistance and applications sciencedirect. We are going to treat the magnetoresistance of metals in a quite general and simple manner. 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.
Other articles where magnetoresistance is discussed. 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. There are a variety of effects that can be called magnetoresistance. Giant magnetoresistance did not get its name by being a small effect. Start this article has been rated as startclass on the projects quality scale.