In 1988 two solidstate physicists discovered that alternate ultrathin layers of iron and chromium, each layer a few atoms thick, showed a very large drop in resistivity under an applied magnetic field. Giant magnetoresistance of 001fe001 cr magnetic superlattices. The asymmetric magnetic potential is achieved by combining an. In this contribution, we first focus on the links between effect characteristic and underlying microstructure. The highly sensitive magneticbased biomolecule detection system can identify the presence of antigens, dna fragments, biomarkers or other biomolecules using magnetic nanoparticles, an applied magnetic field and a giant magnetoresistance gmr sensor that detects the presence of nanoparticle tagged biomolecules. The effect had been known for a long time but not at such an amplitude, which is why it was called giant magnetoresistance or 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. The term giant magnetoresistance gmr has come to be associated with certain thin metallic multi. Giant magnetoresistance effect in organic material and its potential for magnetic sensor mitra djamal1, ramli2, sparisoma viridi3 and khairurrijal4 1department of physics, institut teknologi bandung, bandung, indonesia. Subscribe today and give the gift of knowledge to yourself or a friend magnetoresistance giant magnetoresistance and you magnetoresistance, giant magnetoresistance, and you. Pdf theory of giant magnetoresistance in granular alloys. A similar, though diminished effect was simultaneously discovered in fecrfe trilayers. The 2007 nobel prize in physics was awarded to albert fert and peter grunberg for the discovery of gmr. Within a decade of gmr being discovered in 1988 commercial devices based on this phenomenon.
Giant magnetoresistance gmr is a quantum mechanical magnetoresistance. Magnetoresistance is a phenomenon in which the electrical resistivity of a material changes in the presence of an external magnetic eld. Highthroughput giant magnetoresistance biomoleculesensing system. Magnetic field sensors based on giant magnetoresistance.
If the insulating layer is thin enough typically a few nanometres, electrons. Theory of spin torques and giant magnetoresistance in. Theory of giant magnetoresistance effects in magnetic layered structures with antiferromagnetic coupling. The kubo formalism 8 uses linear response theory to calculate the. On the theory of giant magnetoresistance longitudinal current. It specifically requires a particular layered structure.
H is the resistivity in the presence of a magnetic. One example of a novel detection method is a biosensor, presented by edan instruments shenzhen, china, using magnetic beads to measure immunocomplex formation by means of giant magnetoresistance. The calculated optimistic tmr ratio is in excess of % for an mgo barrier of 20 atomic planes and the spin polarization of the tunneling current is positive for all mgo thicknesses. The phenomenon has its origin deep in quantum theory.
A theory of giant magnetoresistance in granular alloys was developed by considering the spindependent scattering within the magnetic granules and at their boundaries and the continuous distributions of granule sizes and directions of magnetization. Pdf giant magnetoresistance of 001fe001cr magnetic. Pdf the giant magnetoresistance gmr effect is a very basic. The magnetoresistance at bias voltages up to 1,300 mv was measured at 293 k and 20 k by using the d.
Typical magnetoresistance curves for the femgofeirmn mtj at 293. Tunnel magnetoresistance effect and its applications. A brief introduction to giant magnetoresistance arxiv. Giant magnetoresistance gmr is a quantum magnetorisitance effect observed in thin film structures composed of alternating ferromagnetic and non magnetic layers. They demonstrated that the electric current in a magnetic multilayer consisting of a sequence of thin magnetic layers separated by equally thin nonmagnetic. Theory of giant magnetoresistance in granular alloys. On the theory of giant magnetoresistance longitudinal. The calculated optimistic tmr ratio is in excess of % for an mgo barrier of 20 atomic planes and the spin polarization of the tunneling current is. Request pdf theory of spin torques and giant magnetoresistance in antiferromagnetic metals spintronics in ferromagnetic metals is built on a complementary set of phenomena in which magnetic.
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. 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. Tmr can be understood in terms of jullieres model, which is based on two assumptions. Giant magnetoresistance gmr spin dependent scattering, two current channels, one for majority spins often low resistivity. Introduction giant magnetoresistance gmr is a device in which the resistance is change by the influence of magnetic field. Albert fert and peter grunberg were jointly awarded the nobel prize for the discovery of giant magnetoresistance in 2007. In epitaxy create materials that display giant magnetoresistance a property that has been used to produce higherdensity digital storage devices. Whats the explanation for the giant magnetoresistance effect. Giant magnetoresistance effect in organic material and its. Giant magnetoresistance is the observation that current flows differently across a multilayer stack consisting of alternating metallic fmmetal bilayers if the magnetization of adjacent ferromagnetic layers is aligned or antialigned barthelemy et al. Giant magnetoresistance effect in organic material and its potential for magnetic sensor mitra djamal1, ramli2, sparisoma viridi3 and khairurrijal4 1department of physics, institut teknologi bandung, bandung, indonesia tel. The giant magnetoresistance gmr effect is a very basic.
Giant magnetoresistance and the spinvalve head of the giant magnetoresistance 6,7, was actually to build magnetic 2. Theory of the perpendicular magnetoresistance in magnetic multilayers. The effect relies on the middle layer being very thin such that quantum effects of electron spin can be prese. 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. Magneto resistor is a type of resistor whose resistance changes when an external magnetic field is applied. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. It should be noted that calculations made in the slab geometry fig. Giant magnetoresistance gmr is one of the most fascinating discoveries in thinfilm magnetism, which combines both tremendous technological potential and deep fundamental physics. In other words, the flow of electric current through the magneto resistor changes when an external magnetic field is applied to it. Since 1988 with the discovery of the giant magnetoresistance gmr in metallic mag. A brief introduction is given to gmr effects from scientific background to experimental observations and theoretical models. 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. 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. Calculation of the tunneling magnetoresistance of an epitaxial femgofe001 junction is also described.
As was shown later, high magnetoresistance values can also be obtained in other magnetic multilayers, such as cocu. Subscribe today and give the gift of knowledge to yourself or a friend magnetoresistance and giant magnetoresistance and introduction to atoms and energies. Giant magnetoresistance of magnetic multilayers technische. Gmr structure is thin film composed by alternating ferromagnetic f and nonmagnetic n layers. Publishers pdf, also known as version of record includes final page. Typical magnetoresistance curves for the femgofeirmn mtj at 293 k and 20 k are shown in fig. Ando tunnel magnetoresistance effect and its applications. Giant magnetoresistance gmr is one of the most fascinating discoveries in thin film. Giant magnetoresistance in magnetic multilayered systems.
In 2015, scientists discovered a new magnetoresistance effectthat is, a new way in which magnetization affects a materials electric resistancebut hadnt yet found a promising. All theories on the giant magnetoresistance effect developed thus far, predict a. 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. Giant magnetoresistance and quantum transport in magnetic. Oct 28, 2017 subscribe today and give the gift of knowledge to yourself or a friend magnetoresistance and giant magnetoresistance and introduction to atoms and energies. Giant magnetoresistance biomolecule sensing system. 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. Basic concepts, microstructure, magnetic interactions and applications. New magnetoresistance effect leads to fourstate memory device. We are going to treat the magnetoresistance of metals in a quite general and simple manner. 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. 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 asymmetric magnetic potential is achieved by combining an external magnetic.
If the insulating layer is thin enough typically a few nanometres, electrons can tunnel from one ferromagnet into the other. In typical metal, at room temperature, orbital mr effects are very small, at most of the order of a few per cent. 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 gmr. Giant magnetoresistance simple english wikipedia, the free. Since the discovery of gmr the theoretical treatment of this effect became the. This chapter describes the theory of the giant magnetoresistance effect and the. A brief introduction to giant magnetoresistance liu chang1, min wang1, lei liu1, siwei luo2, pan xiao1, 1hycorelle co. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in multilayers composed of alternating ferromagnetic and nonmagnetic conductive layers.
Giant magnetoresistance simple english wikipedia, the. Theory of giant magnetoresistance and tunneling magnetoresistance. For a sphericallysymmetric energy spectrum therefore, the xxcomponent is field independent. There are a variety of effects that can be called magnetoresistance. In principle, a complete bottomtype could then be grown on. Magnetoresistance is the tendency of a material often ferromagnetic to change the value of its electrical resistance in an externallyapplied magnetic field. This change in resistance, in general a reduction, is related to the fieldinduced alignment of the magnetizations of the magnetic. The first hard disk drives hdds date back to the 1950s. Therefore, the sequential introduction of the magne. Giant magnetoresistance an overview sciencedirect topics. Giant magnetoresistance did not get its name by being a small effect. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and. Giant magnetoresistance gmr is a very small magnetic effect found in thin layers of iron and other materials. 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.
It is also a way to control the electrical resistance at the nano scale using magnetic field. Giant magnetoresistance is a change in resistance caused by a magnetic field. Tunneling magnetoresistance evgeny tsymbal nebraska. Pdf the 2007 nobel prize in physics was awarded to albert fert and peter grunberg for the discovery of giant magnetoresistance gmr. Giant magnetoresistance shows great promise for the next generation of magnetic reading devices. The standard spin valve shows about 56 % magnetoresistance. Just like ordinary magnetoresistance, giant magnetoresistance can be used to read magnetic data by monitoring the change in current as magnetic data passes by the superlattice. 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. Magnetoresistance was discovered by lord kelvinwilliam thomson in 1851. 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.