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Organisms have extremely low-frequency(below hundreds of Hz) weak magnetic field strength signals, such as the human heart, brain and other magnetic field signals, which are often even smaller at the pT level. It is of great significance to detect and locate diseases such as myocardial infarction and coronary heart disease in the human body by detecting magnetic field signals. Because the whispering gallery mode(WGM) microcavity has a high quality factor and a small mode volume, it can effectively amplify the interaction between substances, so it is an excellent platform for realizing ultra-high magnetic sensing sensitivity. By combining whispering gallery mode microcavities with magnetostrictive materials, highly sensitive magnetic sensors can be designed and fabricated. However, at present, the main application of microcavity magnetic sensor is in high frequency, and the detection of low frequency magnetic field is still difficult. We optimized the structural parameters of the sensor including the device radius, device thickness, base radius, magnetostrictive material type, microcavity structure and other parameters, significantly reducing the eigenfrequency of the sensor. The eigenfrequency of the sensor can reach 67 Hz, when the cavity with 1.5 mm radius size. The sensor eigenfrequency can be reduced to hundreds of Hz, in radius sizes of hundreds of micrometers. It will pave the way for the applications in low-frequency magnetic field detection.
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