The ultimate goal of the project is to realise a new miniaturised and ultra-sensitive magnetometer that can be used in space on all kinds of platforms, including nanosatellites.
This new magnetometer, called MAROT (Low noise MAgnetometeR based On Tunnel junctions), is based on improved magnetic tunnel junctions.
Compared to state-of-the-art magnetometers used in space, this new magnetometer is designed to provide a gain of more than one order of magnitude in mass and size while keeping or improving the performances. Therefore, it aims at combining and replacing, within a single instrument concept, two different kinds of magnetometers (fluxgates and search coils) that are currently used in most space missions. These instruments having significant volume and mass (400g to 700g for 3 measurement axes), MAROT will be a real breakthrough regarding its 10 times smaller dimensions and mass with similar or better performances. Our prediction, based on theory as well as a first manufacturing, is to reach a sensitivity of 100fT/Hz-1/2 on a frequency band from DC to 1kHz, on a chip with dimensions 10x4mm and a mass of 1g for 1 measurement axis.
In addition, with the innovative junction, a real improvement is foreseen compared to existing technology. Indeed, standard magnetic tunnel junctions have a recurrent limitation: they are changing their working mode (and thus their calibration) when submitted to a strong magnetic field. The innovative junction we intend to develop shall correct for this defect. Moreover, design work on the geometry of the ferromagnetic layers in the junction will lead to increase the sensitivity of the sensor.
The instrumental concept of MAROT benefits from the skills of our two laboratories: LPC2E, specialised in the realisation of magnetic sensors for various national and international space missions (CNES, ESA, NASA), and SPINTEC, specialised in developments related to spin electronics. The sensor is made of a chip including:
– 2 magnetic tunnel junctions as the sensitive unit of the sensor
– 4 flux concentrators made by electrolytic deposition to amplify the measured magnetic field
– 4 polarisation coils inserted in the substrate thanks to lithography and etching technics
Several steps have already been realised towards the realisation of this project. The funding provided by ATTRACT will therefore allow us to reach a major milestone, which is to obtain a fully manufactured sensor demonstrating its capabilities. The conditioning of the instrument for its space use will start right after the end of the project.
Following a first manufacturing test, we identified the technological steps below to deal with during the project period:
– Optimisation of an innovative magnetic tunnel junction
– Improvement of the flux concentrator to increase the sensor’s gain
– Improvement of the micro fabrication process reliability to ensure as many operational sensors as possible on a wafer
– Development of the associated electronic circuits