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The change of electrical resistance produced in a current-carrying conductor or semiconductor on application of a magnetic field H. Magnetoresistance is one of the galvanomagnetic effects. It is observed with H both parallel to and transverse to the current flow. The change of resistance usually is proportional to H2 for small fields, but at high fields it can rise faster than H2, increase linearly with H, or tend to a constant (that is, saturate), depending on the material. In most nonmagnetic solids the magnetoresistance is positive. See Galvanomagnetic effects

In semiconductors, the magnetoresistance is unusually large and is highly anisotropic with respect to the angle between the field direction and the current flow in single crystals. When the magnetoresistance is measured as a function of field, it is the basis for the Shubnikov–de Haas effect, much as the field dependence of the magnetization gives rise to the de Haas-van Alphen effect. Measurement of either effect as the field direction changes with respect to the crystal axes serves as a powerful probe of the Fermi surface. Magnetoresistance measurements also yield information about current carrier mobilities. Important to practical applications is the fact that the geometry of a semiconductor sample can generate very large magnetoresistance, as in the Corbino disk. See De Haas-van Alphen effect, Fermi surface, Semiconductor

Multilayered structures composed of alternating layers of magnetic and nonmagnetic metals, such as iron/chromium or cobalt/copper, can feature very large, negative values of magnetoresistance. This effect, called giant magnetoresistance, arises from the spin dependence of the electron scattering which causes resistance. When consecutive magnetic layers have their magnetizations antiparallel (antiferromagnetic alignment), the resistance of the structure is larger than when they are parallel (ferromagnetic alignment). Since the magnetic alignment can be changed with an applied magnetic field, the resistance of the structure is sensitive to the field. Giant magnetoresistance can also be observed in a simpler structure known as a spin valve, which consists of a nonmagnetic layer (for example, copper) sandwiched between two ferromagnetic layers (for example, cobalt). The magnetization direction in one of the ferromagnetic layers is fixed by an antiferromagnetic coating on the outside, while the magnetization direction in the other layer, and hence the resistance of the structure, can be changed by an external magnetic field. Films of nonmagnetic metals containing ferromagnetic granules, such as cobalt precipitates in copper, have been found to exhibit giant magnetoresistance as well. See Antiferromagnetism, Ferromagnetism, Magnetization

Magnetoresistors, especially those consisting of semiconductors such as indium antimonide or ferromagnets such as permalloy, are important to a variety of devices which detect magnetic fields. These include magnetic recording heads and position and speed sensors. See Magnetic materials

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a change in the electric resistance of a solid conductor caused by an external magnetic field. A distinction is made between transverse magnetoresistance, in which the electric current flows at right angles to the magnetic field, and longitudinal magnetoresistance, in which the current flows parallel to the magnetic field.

Magnetoresistance results from distortion of the trajectories of the current carriers in a magnetic field. In semiconductors the relative change in resistance Δp/p is 100-10,000 times greater than in metals and can reach hundreds of percent. Magnetoresistance is a galvanomagnetic phenomenon. It is used to study the electron energy spectrum and the mechanism of scattering of current carriers in a crystal lattice, and also to measure magnetic fields.


Lifshits, I. M., M. Ia. Azbel’, and M. I. Kaganov. Elektronnaia teoriia metallov. Moscow, 1971.
Blatt, F. Fizika elektronnoi provodimosti v tverdykh telakh. Moscow, 1971. (Translated from English.)
Ansel’m, A. I. Vvedenie v teoriiu poluprovodnikov. Moscow-Leningrad, 1962.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The change in the electrical resistance of a material when it is subjected to an applied magnetic field, this property has widespread application in sensors and magnetic read heads.
The change in electrical resistance produced in a current-carrying conductor or semiconductor on application of a magnetic field.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


A change in electrical resistance in metal or a semiconductor when it is subjected to a magnetic field. The property of magnetoresistance is used in reading the bits on magnetic tape and disk. Although used in earlier analog tape recorders, in 1991, IBM was the first to use a magnetoresistive (MR) read head in a computer disk drive.

Magnetoresistive (MR)
As storage capacity increases, the bit gets smaller and its magnetic field becomes weaker. MR heads are more sensitive to weaker fields than earlier inductive read coils, in which the bit on the medium induced the current across a gap. The MR mechanism is an active element with current flowing through it. The magnetic orientation of the bit increases the resistance in a thin-film nickel-iron layer, and the difference in current is detected by the read electronics. MR heads use the traditional inductive coil for writing.

Giant MR
In 1998, IBM introduced drives with giant MR (GMR) heads, which are sensitive to even weaker fields. GMR heads use additional thin film layers in the sensing element to boost the change in resistance, and "giant" refers to this larger change. Almost all modern drives use GMR read heads.

Extraordinary MR
Discovered in 1995 at the NEC Research Institute in Princeton, NJ, extraordinary MR (EMR) provides an even greater change in resistance. Quite unique in that the material is non-magnetic, EMR is expected to provide bit densities of a terabit per square inch some day. See superparamagnetic limit.

GMR Heads for Reading
Most modern disk drives use GMR (giant MR) heads for reading, but use inductive coils for writing. (Illustration assistance courtesy of Hitachi Global Storage Technologies.)
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References in periodicals archive ?
*1 STT-MRAM refers to magnetoresistive random-access memory (MRAM) which utilizes a technology known as spin-transfer torque (STT) for writing data.
The use of such signal processing methods with low-cost sensors, such as magnetoresistive sensors, can lead to the development of low-initial-cost and maintenance-free magnetocardiography systems, which in the near future may replace the electrocardiogram now routinely used in hospitals.
Prinz, "Ultrahigh density vertical magnetoresistive random access memory (invited)," Journal of Applied Physics, vol.
In recent years, magnetoresistive magnetic sensors have been developed for vehicular applications, because they are sensitive, small and more immune to environmental factors such as rain, wind, snow or fog, hence offering definite advantages over other vehicular sensing systems based on video cameras, ultrasound or infrared radiation.
About 150 years ago it was established experimentally that when the conductor is placed with an electric current in an external magnetic field, its reactance [R.sub.e] slightly changes [10], This phenomenon was called the magnetoresistive effect--the <<magnetoresistance>> of the conductor [R.sub.em] [4, 8], The nature of the established dependence for [R.sub.e] on the level of the intensity [H.sub.m] of the external magnetic field was then unknown.
It provides theoretical explanations for new systems, techniques, and databases like GFS and HDFS (Google and Hadoop file systems), MapReduce, Cassandra, Neo4j, and MongoDB; outlines traditional algorithms like mergesort, B-trees, and hashing; discusses the foundations of different technologies and use cases for them; and details physical storage hardware like hard disk drives, solid-state drives, and magnetoresistive RAM to understand how they function and affect the complexity, performance, and capabilities of existing storage and analytics algorithms.
The company says the new, fully scalable magnetoresistive speed and angle measurement system has a pulse frequency up to 8,192 pulses per revolution, with twin tracks displaced by 90[degrees] to provide clockwise and anticlockwise indication.
Li, "Attitude determination method and experimental research based on MEMS IMU and magnetoresistive sensor," in Proceedings of the 11 th IEEE International Conference on Mechatronics and Automation (ICMA '14), pp.
As magnetic sensitive electric component mainly hall sensor or magnetoresistive sensors are used [1-4].
Caruso, "Applications of magnetoresistive sensors in navigation systems", SAE Technical Papers, vol.
Within the accelerometer family you can find various categories depending on how the accelerometer senses the change in acceleration, such as capacitive (change in capacitance related to acceleration), piezoelectric (uses microcrystals to determine voltage output converted to acceleration), Hall effect (changing magnetic fields), magnetoresistive (change in magnetic field), heat transfer, and piezoresistive (change in electrical resistance).
Nowadays technologies based on two different magnetoresistive effects are applied in automobiles.