Double-Gap Magnetic Flux Concentrator Design for High-Sensitivity Magnetic Tunnel Junction Sensors.

Jiafei Hu,Huiyan Liu,Weicheng Qiu,Peisen Li,Minhui Ji,Junping Peng,Long Pan,Yueguo Hu,Mengchun Pan

doi:10.3390/s19204475

Jiafei Hu, Huiyan Liu + Show 7 more

Open Access

https://doi.org/10.3390/s19204475

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Abstract

To improve the sensitivity of the magnetic tunnel junction(MTJ)sensor, a novel architecture for a double-gap magnetic flux concentrator (MFC) was studied theoretically and experimentally in this paper. The three-dimensional finite element model of magnetic flux was established to optimize the magnetic field amplification factor, with different gaps. The simulation results indicate that the sensitivity of an MTJ sensor with a double-gap MFC can be significantly better than that of a sensor with a traditional single-gap MFC, due to the fact that the magnetic magnification sharply increases with the decrease in effective gap width. Besides this, the half-bridge MTJ sensors with the double-gap MFC were fabricated using photolithography, ion milling, evaporation, and electroplating processes. Experimental results show that the sensitivity of the MTJ sensor increased by ten times compared to the sensor without the double-gap MFC, which underlines the theoretical predictions. Furthermore, there is no significant increase in the sensor noise. The work in this paper contributes to the development of high-performance MTJ sensors.

Highlights

The magnetic tunnel junction (MTJ) sensor is based on the effect of tunneling magnetoresistance (TMR), which has had a major role in biomedicine, industry, and geophysics due to its high sensitivity and low power consumption [1,2,3]
In order to obtain a high-performance MTJ sensor with high magnetic sensitivity and low noise, this paper proposes a novel architecture of double-gap magnetic flux concentrator (MFC) designed to achieve an improved half-bridge sensitivity
In order to verify this double-gap proposal, an MTJ half bridge sensor integrated with double-gap NiFe MFC was fabricated, which consisted of four MTJ bridge arms

Summary

Introduction

The magnetic tunnel junction (MTJ) sensor is based on the effect of tunneling magnetoresistance (TMR), which has had a major role in biomedicine, industry, and geophysics due to its high sensitivity and low power consumption [1,2,3]. The structure of the Wheatstone bridge is commonly used in MTJ sensors [7]. It is well known that a full Wheatstone bridge can get a linear output, but the technological process is relatively complex due to the need for precise design of different sensitive axes. To simplify the production process, the structure of the half bridge is a reliable alternative to suppress noises, which includes two sensitive arms and two reference arms [8,9].

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Discussion

Conclusion