Typical magnetoresistance curves for the femgofeirmn mtj at 293 k and 20 k are shown in fig. Rigorous theory of the tunneling magnetoresistance tmr based on the realspace kubo formula and fully realistic tightbinding bands fitted to an ab initio band structure is decribed. The magnetoresistance is characterized by ppms at 2 k with a magnetic field from. Negative magnetoresistance in dirac semimetal cd 3 as 2. Coils of wire are still used to write magnetic data, since a change in resistance does not cause a magnetic field. Magnetoresistance article about magnetoresistance by the. Inductive heads can give about a 1% effect, while magnetoresistance heads give about a 4% effect. A recently introduced percolative theory of unipolar organic magnetoresistance is generalized by treating the hyperfine interaction semiclassically for an arbitrary hopping rate. 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. Universal properties of linear magnetoresistance in strongly disordered semiconductors h. The traditional explanation of the tmr effect is based on the assumption that electrons tunneling from a ferromagnet are. Compact analytic results for the magnetoresistance are achievable when carrier hopping occurs much more frequently than the hyperfine field precession period.
Characterization and measurement surface potential measurement. Magnetoresistance is a general term for the changes in the components of the resistivity and conductivity tensors of materials caused by the application of magnetic. Giant magnetoresistance gmr is a very small magnetic effect found in thin layers of iron and other materials. Magneto resistor definition, working, types, and applications. Heinonen, a quantum approach to condensed matter physics cambridge university press, new york, 2002 a modern, intermediate level treatment of the quantum theory of solids.
A large negative magnetoresistance nmr is anticipated in topological semimetals in parallel magnetic fields, demonstrating the chiral anomaly, a longsought highenergyphysics effect, in solid. Magnetic field is the region present around a magnetic object within which. Magneto resistor is a type of resistor whose resistance changes when an external magnetic field is applied. Pdf recent experimental studies of magnetoresistance in disordered superconducting thin films on the insulating side of the superconductorinsulator. Percolation model for organic magnetoresistance simulation 4. Theory of the resistivity and magneto resistance of metals at. The effect of the crystalstructuredependent anisotropy of the electron distribution function on the resistivity p, magnetoresistance ph and hall coefficient r at.
Twoband theory analysis of the magnetoresistance and the hall resistivity curves at different temperatures fig. Tunnel magnetoresistance effect and its applications. Heiman1 1department of physics, northeastern university, boston, ma 02115 2department of mechanical engineering, northeastern university, boston, ma 02115 3department of chemical engineering, northeastern university. Hall e ect and magnetoresistance hall e ect and magnetoresistance predictions from the drude model magnetoresistance and hall coe cient consider once again the equations. We present a theory of the spin hall magnetoresistance smr in multilayers made from an insulating ferromagnet f, such as yttrium iron garnet yig, and a normal metal n with spinorbit interactions, such as platinum pt. Based on the theories so far developed, an approximate expression for the resistivity of metallic films is supplemented the fuchssondheimer theory,1,2. Giant magnetoresistance gmr is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating. Tunneling magnetoresistance evgeny tsymbal nebraska. On the theory of giant magnetoresistance longitudinal. The pdf analysis played a major role in this process and also provided. The term giant magnetoresistance gmr has come to be associated with certain thin metallic multi. The magnetoresistance at bias voltages up to 1,300 mv was measured at 293 k and 20 k by using the d.
Ibm started using magnetoresistance in its read heads in 1992. Universal properties of linear magnetoresistance in. Magnetoresistance is the tendency of a material to change the value of its electrical resistance in an externallyapplied magnetic field. Classically, the mreffect depends on boththe strength ofthe magnetic field and the relative direction ofthe magnetic field with respect to the current. Mathon departmentofmathematics,cityuniversity,londonec1v0hb,uk rigoroustheoryofthetunnelingmagnetoresistance tmrbasedontherealspacekuboformulaandfully realistictightbindingbandsfittedtoanabinitiobandstructureisdescribed. In both cases, the weakfield mr with strong temperature dependence can be expressed as ln r h r 0. The finding of an extremely large magnetoresistance effect on silicon based pn junction with vertical geometry over a wide range of temperatures and magnetic fields is reported. 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. Lecture notes on condensed matter physics a work in. Magnetoresistance is the tendency of a material often ferromagnetic to change the value of its electrical resistance in an externallyapplied magnetic field. Magnetoresistance mr in general is nonzero and anisotropic. The magnetization dependence of resistance is of great interest due to the applica. Magnetoresistance overview janicenickel computerperipheralslaboratory hpl9560 june, 1995 magnetoresistance, sal, dualstripe, spinvalve, gmr magnetoresistance, the change of a materials resistivity with the application of a magnetic field, is a well known phenomenon.
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. A large magnetoresistance effect in pn junction devices. Most of the magnetoresistive devices are built upon ferromagnetic materials and we will concentrate. Elsevier physica b 217 1996 102 106 magnetoresistance of upd2ge2 h. Theory of magnetoresistance in threedimensional dirac. The theory of positive magnetoresistance has been developed for two cases, without and with electronelectron interactions. Linear polarization study of microwaveradiationinduced magnetoresistance oscillations. To use the instrument correctly and safely, read and follow the precautions in table 1 and. Tem sample preparation thin foils for stem observations were prepared by a conventional method that includes mechanical polishing of the sample back and then ionbeam milling. Micrometric devices are normally patterned by means of optical lithography techniques nanometric devices are normally patterned by means of electronbeam lithography, focused ion beam lithography, nanoimprinting, etc. Magnetoresistance definition of magnetoresistance by. Other articles where magnetoresistance is discussed. For a sphericallysymmetric energy spectrum therefore, the xxcomponent is field independent. Magnetoresistance results from distortion of the trajectories of the current carriers in a magnetic field.
Tmr can be understood in terms of jullieres model, which is based on two assumptions. In other words, the flow of electric current through the magneto resistor changes when an external magnetic field is applied to it. A spectacular anisotropy observed in cu is explained based on the nonspherical fermi surface of this metal in this chapter. Giant magnetoresistance 2 magnetoresistance mr is the change of resistance of a conductor in an external magnetic field. Giant magnetoresistance and tunneling magnetoresistance arise when a magnetic field reorients the magnetization in different regions of a specimen causing a change in electrical resistance. This chapter describes the theory of the giant magnetoresistance effect and the tunneling magnetoresistance effect. Semiclassical theory of magnetoresistance in positionally. B, condensed matter 735 february 2006 with 151 reads.
A brief introduction to giant magnetoresistance liu chang1, min wang1, lei liu1, siwei luo2, pan xiao1, 1hycorelle co. We are going to treat the magnetore sistance of metals in a quite general and simple manner. Effects of weak localization and charge inhomogeneity yungfu chenn, myungho bae, cesar chialvo, travis dirks, alexey bezryadin, nadya mason department of physics and materials research laboratory, university of illinois at urbanachampaign, urbana, il 618012902, usa. In typical metal, at room temperature, orbital mr effects are very small, at most of the order of a few per cent. An advanced level text on the quantum theory of solids, treating phonons, electrons, plasmons, and photons. The theory of positive magnetoresistance has been developed for two cases, without.
Digital gaussmeter, dgm102 1 four probe arrangement. 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. By 1994, all read heads produced by ibm were using magnetoresistance. Magnetoresistance, where the resistance of the material changes with applied magnetic field, occurs in all metals. High magneticfield sensitivity organic single crystal. Itisfirstappliedtocalculatethe tmr of two co electrodes separated by a vacuum gap. The dashed lines are fitted curves which agree with the experimental data solid lines well. If the insulating layer is thin enough typically a few nanometres, electrons can tunnel from one ferromagnet into the other. We are going to treat the magnetoresistance of metals in a quite general and simple manner. Theory of the perpendicular magnetoresistance in magnetic multilayers. Since this process is forbidden in classical physics, the. Negative and positive magnetoresistance in bilayer.
Twoband theory analysis of the magnetoresistance a and the hall resistivity b curves at different temperatures. In semiconductors the relative change in resistance. Magnetoresistance effect is the change of resistance denoted by. Magnetoresistance an overview sciencedirect topics. Atomic origin of spinvalve magnetoresistance at the. Device fabrication preparation of single crystals device fabrication 2.
Giant magnetoresistance simple english wikipedia, the. There are a variety of effects that can be called magnetoresistance. The magnitude of the effect in materials used in the recording industry has. Theory of giant magnetoresistance effects in magnetic layered structures with antiferromagnetic coupling. Gmr is kind of like magnetoresistance on steroids, and was indeed a giant step for mankind when it was discovered in. Wh b adepartment of physics, national cheng kung university, tainan, 701, taiwan bdepartment of physics, national tsing hua university, hsinchu, 300, taiwan. Linear polarization study of microwaveradiationinduced. The paper has been permanently removed due to issues. Negative and positive magnetoresistance in bilayer graphene. Experimented setup for magnetoresistance the setup consists of the following. H is the resistivity in the presence of a magnetic. Comparison of power dependence to theory by tianyu ye, jesus inarrea, w. According to the boltzmann transport theory, the electrical conductivity can be theory of fuchs and sondheimer of scattering at interfaces, is utilized. Other effects occur in magnetic metals, such as negative magnetoresistance in ferromagnets or anisotropic magne.
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