Optimization of a Wedge Shaped T-Type Magnetic Flux Concentrator for High-Sensitivity TMR Sensors

A Wedge Shaped T-Type magnetic flux concentrator (MFC) is proposed to improve the magnetic detection capability of tunneling magnetoresistance (TMR) sensors. The TMR chip used in this work integrates a CoFeSiB soft magnetic thin film on-chip and exhibits a sensitivity of 251 mV/Oe with a magnetic noise of 65.3 pT/sqrt(Hz). Based on magnetic circuit analysis and finite-element simulations, the key structural parameters of the Wedge Shaped T-Type MFC were optimized, including the air-gap distance, aspect ratio, and input-output cross-sectional ratio. The optimal parameters were determined as an air gap of 200 μm, an aspect ratio of 2, and a cross-sectional compression ratio exceeding 100. Sixteen MFC structures with different sizes were fabricated and integrated with the TMR sensors for experimental evaluation. The results show that the external flux concentrator does not introduce additional voltage noise while significantly improving the sensor response. With optimized structures, the sensor sensitivity increases from 251 mV/Oe to 17,812 mV/Oe, and the magnetic noise is reduced from 65.3 pT/sqrt(Hz) to 0.92 pT/sqrt(Hz) at 1 Hz. The experimental results demonstrate that the Wedge Shaped T-Type MFC effectively enhances the magnetic field gain and significantly improves the detection limit of TMR sensors.