Abstract: An integrating magnetic sensor is described which comprises a sensor element made from a filament of substantially amorphous material which exhibits giant magneto-impedance and means for applying a bias field to the said sensor element so that it operates in the high field section of the giant magneto-impedance response.

Abstract: A magnetic field sensor including a body of amorphous magnetic material [C] and means to propagate ultrasound [A.B.D.] in said body together with means [E,F; PD, PSD, F] to detect variation with ambient magnetic field strength in the effect of the body on the propagation of ultrasound therein. The ultrasound is propagated as zero-mode shear wave, said mode being controlled by having the thickness of the body of amorphous magnetic material below a critical value which is the quotient of velocity divided by frequency. A specific magnetic field [G,J; G,M] can be applied to control the operating point of the sensor. The field can be alternating and the effect on propagation detected by a phase detector followed by a phase sensitive detector.