Magnetoresistance is the property of some materials to change the value of their electrical resistance when an external magnetic field is applied to them. The effect was first discovered by William Thomson in 1856, but he was unable to lower the electrical resistance of anything by more than 5%. This effect was later called ordinary magnetoresistance (OMR). More recent researchers discovered materials showing giant magnetoresistance (GMR), colossal magnetoresistance (CMR) and magnetic tunnel effect (TMR). Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges and magnetic dipoles, such as those in electric currents and magnets. ... William Thomson, 1st Baron Kelvin, OM, GCVO, PC, PRS, FRSE, (26 June 1824 – 17 December 1907) was a mathematical physicist, engineer, and outstanding leader in the physical sciences of the 19th century. ... 1856 was a leap year starting on Tuesday (see link for calendar). ... The Giant Magnetoresistive Effect (GMR) is a quantum mechanical effect observed in thin film structures composed of alternating ferromagnetic and nonmagnetic layers. ... Colossal magnetoresistance (CMR) is a property of some materials, mostly manganese-based perovskite oxides, that enables them to dramatically change their electrical resistance in the presence of a magnetic field. ... If two ferromagnets are separated by a thin (about 1 nm) insulator, the resistance of the tunneling current changes with the relative orientation of the two magnetic layers. ...

Anisotropic magnetoresistance (AMR)

A material property demonstrating a dependence of electrical resistance on angle between the direction of electrical current flow and orientation of magnetic field. The effect is attributed to a larger probability of s-d scattering of electrons in the direction of magnetic field. The net effect is that the electrical resistance has maximum value when the direction of current is parallel to the applied magnetic field.

In a semiconductor with a single carrier type, the magnetoresistance is proportional to (1+ (μB)²), where μ is the semiconductor mobility (units m^2·V^-1·s^-1 or T ^-1) and B is the magnetic field (units teslas). Indium antimonide, an example of a high mobility semiconductor, could have an electron mobility above 4 m²·V^-1·s^-1 at 300 K. So in a 0.25 T field, for example the magnetoresistance increase would be 100%. A semiconductor is a fuckin solid whose electrical conductivity is in between that of a metal and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... This does not adequately cite its references or sources. ... SI unit. ... Indium antimonide (InSb) is a narrow gap semiconductor material from the group the (III-V group) used in infrared detectors, including thermal imaging cameras, FLIR systems, infrared homing missile guidance systems, and in infrared astronomy. ...

To compensate the nonlinear characteristics and inability to detect the polarity of magnetic field, somewhat more complex structure is used for sensors. It consists of stripes of aluminium or gold placed on a thin film of permalloy (feromagnetic material showing AMR effect) inclined by angle of 45°. This structure forces the current not to flow along the “easy axes” of thin film, but at angle of 45°. The dependence of resistance now has a permanent offset and it's linear around the nul-point. Because of its appearance, this structure is called barber-pole. Permalloy is a nickel iron alloy with about 20% iron and 80% nickel content. ...

AMR effect is used for wide array of sensors for measurement of Earth magnetic field (electronic compass), for electrical current measuring (by measuring the magnetic field created around the conductor), for traffic detection and for linear position and angle sensing. The biggest AMR sensor manufacturers are Honeywell, NXP Semiconductors, and Sensitec GmbH. Compass in a wooden box A compass (or mariners compass) is a navigational instrument for finding directions on the Earth. ... Honeywell Heating Specialties Company Stock Certificate dated 1924 signed by Mark C. Honeywell - courtesy of Scripophily. ... For other uses of NXP, see NXP (disambiguation). ...

See also

Look up magnetoresistance in
Wiktionary, the free dictionary.

• Giant magnetoresistance
• Colossal magnetoresistance