Abstract: Apparatus for detecting an external magnetic field comprises a magnetic sensor which produces para-magnetic oscillations and includes an elongated member of an electrically conductive material and a thin magnetic film disposed thereabout. Alternative embodiments of the invention are presented in each of which the detection of an external magnetic field by the sensor results in a change in the oscillating state. In a first embodiment, the sensor is maintained normally in an oscillating state of a given domain and thus a given phase; when the sensor is subjected to an external magnetic field of appropriate intensity and polarity, the magnetization of the sensor shifts from the first domain to the second domain and accordingly there is produced a change or reversal in phase of the oscillatory output derived from the sensor. In that change of phase, the sensor output passes through a zero voltage value which is detected for providing an indication of the sensing of the external magnetic field.

Abstract: A magnetic substance detecting device is disclosed as being capable of parametric oscillation, and including a magnetic sensor formed of an elongated wire with a magnetic thin film plated on the wire, the film being of uniaxial magnetic anisotropy and having a magnetic hard axis in its axial direction and a magnetic easy axis in its circumferential direction. The magnetic substance to be detected is coupled with a magnetic or electrical circuit associated with the magnetic oscillation domain of the magnetic wire of the magnetic sensor to convert the state of the oscillation output of its detecting coil, thus detecting the magnetic substance.