Material- and fabrication-governed performance of a tunnelling magnetometer

Abstract

Miniaturization of sensitive magnetic sensors for nano- and picosatellites has come to the point where the traditional sensors with magnetic coils can soon be replaced. Thin film technology offers the possibility of making extremely small magnetic field sensors that employ the effect of anisotropic, giant and tunnelling magnetoresistance (AMR, GMR and TMR). In this paper, the development status of sensors based on microelectromechanical systems technology (MEMS), starting from a TMR layer structure, is presented. The sensors have been successfully fabricated and integrated onto an electronic circuit designed for space application. The system as a whole and the sensors in particular have not only been characterized with respect to sensitivity, resolution and noise level but also to launch vibration and space radiation. The sensor performance and limitations are strongly dependent on the deposited materials, sensor design and fabrication process. Since the sensor elements are small and sensitive (with lateral dimensions of some tens of micrometres and resolution of 100 pT at frequencies of MHz), they are also promising for other MEMS applications.