AMR–sensors. All the way up from a deposited thin film to a commercial sensor

Abstract

The anisotropic magnetic resistance effect (AMR), i.e. the change in the electrical resistance of thin ferromagnetic films (e.g. Permalloy) with respect to the direction and amplitude of an external magnetic field is exploited for the fabrication of sensors sensitive for the measurement of lengths, distances, angles, electrical currents, and magnetic fields. The effect is described in a good approximation by R=R ₀-ΔR sin² (ϕ) with ϕ the angle between the electrical current {ie47-1} and the magnetic field {ie47-2} in the thin film. The commercial application of this effect however makes great demands on the fabrication technology. The possibility of its optimization with respect to the sensitivity, and sensor stability (temperature dependence, offset, offset drift, hysteresis) is discussed in some detail.