Compact multi-layer magnetic shields for chip-scale atomic devices

We have designed four sets of multi-layer nested magnetic shields. External diameters for the individual shielding layers range from 3.3 cm to 5.3 cm. The four sets of magnetic shields are tested by fluxgate magnetometer separately. The result of experiment is in excellent agreement with theoretical calculations. The four sets of multi-layer compact magnetic shields made of high-permeability material are compared. The largest shielding factor measured was 32.3 dB for a nested set of three cylinders (Set 2). The nested two spheres structure (Set 4) has the largest uniform region (12 mm). The nested one shell of sphere and one cylinder shell (Set 3) achieve the best trade-off between uniform region and shielding factor.