Design optimization of flux concentrators for magnetic tunnel junctions-based sensors
Thomas Brun, Javier Rial, Lucia Risoli, Johanna Fischer, Philippe Sabon + 4 more
TLDR
This paper optimizes flux concentrator designs for MTJ-based sensors, achieving a 3-order-of-magnitude performance boost by balancing gain and noise.
Key contributions
- Developed a design optimization scheme for MTJ-based sensors to balance flux concentrator gain and magnetic noise.
- Proposed finite element simulations to investigate the influence of air-gap geometry on flux concentrator gain.
- Derived an analytical formula for flux concentrator gain, validated by simulations and based on magnetic reluctance.
- Achieved a three orders of magnitude improvement in sensor detectivity compared to single-junction designs.
Why it matters
Miniaturized, ultra-sensitive magnetometers are crucial for applications like space exploration and health monitoring. This work provides a systematic approach to optimize sensor design, overcoming the trade-off between sensitivity and noise. The resulting performance improvement significantly advances the development of next-generation magnetic sensors.
Original Abstract
Miniaturized, ultra-sensitive and easily integrable magnetometers are needed for many applications, like space exploration or health monitoring. Achieving this goal requires a magnetic sensor with high sensitivity and low noise. High sensitivity (>1000 %/mT) can be obtained by integrating high gain permalloy flux concentrators (FC). And reducing the magnetic 1/f noise can be realized by increasing the number of magnetic tunnel junctions (MTJs) in the air-gap of the FC. However, this is obtained at the expense of a wider air-gap and consequently a decrease of the magnetic gain and thus of the sensitivity. In this paper, we explore a design optimization scheme in order to find the best trade-off between high FC gain and low magnetic noise. To model the gain of the flux concentrator, we propose two complementary approaches; one is based on finite elements simulations of the FC gain where the influence of geometrical parameters of the air-gap is investigated. Then, in a second step, we propose an analytical formula consistent with all our simulations results and based on magnetic reluctance. Finally, we derive an analytical model of the sensor detectivity from which we can extract the optimal sensor design which allows an improvement by three orders of magnitude of the performances compared to a single junction.
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