Study On The Linearization Design And Essential Processes Of Magnetic Tunnel Junction Sensor

The magnetic tunnel junction(MTJ)sensors based on the tunnel magnetoresistance(TMR)effect have been widely used in weak magnetic field detection due to its high sensitivity,small size,low power consumption,low cost and wide response range.The nonlinearity in one of the most important indicators of the sensor,which directly determine the working range and application scenarios of the sensor.For this problem,this paper studies the linearized simulation design and study of the essential processes of the MTJ sensor under the support of the Thirteenth-Five project.The main works of the article are shown as follows:Aiming at the lack of method for linearization design of the MTJ sensor,a method to simulate the performance of the magnetic tunnel junctions based on distributed parameter micromagnetic simulation is proposed.Based on this method,the shape and size of the junction are optimized systematically.The changes of the MTJ performance parameter with the geometric dimension are analyzed,and the simulation results provide an effective reference for the design of the MTJ sensor.To improve the sensitivity of the MTJ sensor with a bridge construction,the simulation model of the magnetic flux concentrator(MFC)is established based on the finite element method,and a double-gap MFC is proposed.The simulation results show that and the magnetic field magnification of the double-gap magnetic concentrator is 3-4times than the single-gap magnetic concentrator,which effectively solve the problem of low magnification of the single-gap MFC.What’s more,a scheme of MTJ sensor structure with the double-gap MFC is designed.This work provides an effectively way for the design of high-sensitivity linearized magnetic sensor.The MTJ sensor was fabricated by using micro-nano processing technology,and in order to get a linear response output,the two-stage annealing post-treatment process was adopted.The parameters of the two-stage annealing were optimized experimentally.Finally,we produce a set of annealing parameters that enable the sensor to obtain a high TMR and a good linearity.The performance of the sensor was comprehensively evaluated by testing the magnetic resistance,output response curve and the noise spectrum under different conditions.And the experiment results show that the nonlinearity of the sensor is 4.1%after optimization,and the sensitivity of the sensor are greatly improved from 1.5%/Oe to 14.5%/Oe.The related results of the thesis provide a good reference for the design of the high-performance magnetic sensor.