A property of some materials in which their resistance is changed by the application of a magnetic field. Some metals show ordinary magnetoresistance. In some exotic compounds containing lanthanum, strontium, manganese, and oxygen (perovskite manganites) the dependence is very strong and is termed colossal magnetoresistance. Other systems display giant magnetoresistance. Magnetoresistive materials are used in magnetic disk heads, replacing old induction coil-based heads.
Magnetoresistance is the property of some materials to change the value of their electrical resistance when an external magnetic field is applied to them. More recent researchers discovered materials showing giant magnetoresistance (GMR), colossal magnetoresistance (CMR) and magnetic tunnel effect (TMR).
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.
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°.
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.
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