Minimizing magnetic fields of the low-noise MnZn ferrite magnetic shield for atomic magnetometer

Abstract

Abstract Several modern precision measurements require a low-noise magnetic shield composed of a MnZn ferrite shield and a multilayer µ -metal shield. However, the residual magnetic field and gradient reduce the performance of the low-noise magnetic shield. An appropriate demagnetization operation is crucial for obtaining a lower residual magnetic field and gradient. This study proposes an improved demagnetization scheme in which the toroidal coil and the solenoidal coil are employed simultaneously, while the ferrite and µ -metal shield layers are wound separately. This allows for a residual field below 0.6 nT and a gradient lower than 0.5 nT cm −1 to be obtained along all three axes within ±20 mm at the center, which is significantly lower than the results published in previous studies. The low-noise magnetic shield used in this study composed of a MnZn ferrite shield with an inner diameter of 112 mm, an outer diameter of 140 mm, and a height of 225 mm, and a five-layer µ -metal shield. This study considerably improves the performance of the low-noise magnetic shields. The proposed scheme can increase the sensitivity of the spin-exchange-relaxation-free atomic magnetometer by approximately 1 fT Hz -1/2 . This study can help apply the low-noise magnetic shield in various fields more conveniently, such as low-field nuclear magnetic resonance detection, atomic gyroscope, and in cutting-edge physics research.