Magnetoresistance

Magnetoresistance is a phenomenon discovered in 1857 by Lord Kelvin. In a magnetic field the resistance of a material varies. This effect has been applied to sensors, for example, in geophysics, but the most important applications have come with the discovery of giant magnetoresistance. Here a much greater drop in resistance is observed than 5%, and this can be used in sensors to measure magnetic fields.

An important application is in reading heads of computer disk drives.