HIGHLY SENSITIVE MAGNETIC SENSOR

A highly sensitive magnetic sensor with a frequency output signal is introduced. The sensor can easily be integrated in an electrical circuit. It consists of a self-starting tunnel (Esaki) diode oscillator in which the necessary inductance is obtained by an electrical, conductive magnetic thin film core. The resistance and inductance of this thin film core is changed drastically by a small external magnetic field in the range of pT to muT Hereby one gets a tuned RF oscillator whose frequency is determined by a weak external magnetic field applied to the thin film core (magnetically controlled oscillator). This low-noise magnetic-field-to-frequency converter is very simple in construction and shows a sensitivity of more than 110 GHz/T. It is suitable for a magnetic readout system or an integrated magnetic sensor array especially for high frequency magnetic heads.