Non-contact temperature determination of embedded magnetic phases of hard coatings by exploitation of the magnetic hysteresis

A non-contact temperature sensor is described which is based on the temperature dependency of the hysteresis of a magnetic phase embedded in a non-magnetic hard coating. For the measurement principle the technique of frequency mixing is used, with extension toward phase sensitivity as indicator for the temperature. The sensor's capabilities such as selectivity and sensitivity are investigated on TiN-FeCo magnetic multilayers. The sensor has been proven for temperatures up to 500 °C and shows capabilities for higher temperatures.