We have designed and tested a set of five miniature nested magnetic shields constructed of high-permeability material, with external volumes for the individual shielding layers ranging from 0.1 to 2.5 cm3. We used two different techniques to measure the shielding factors: a chip-scale atomic magnetometer and a commercially available magnetoresistive sensor. Measurements with the two methods were in good agreement.

Figure 1: A summary of some of the measurements of the transverse shielding factors measured with the microfabricated atomic magnetometer.

We have measured the longitudinal and transverse shielding factors (the ratio of external to internal magnetic field) of both individual shields and combinations of up to three layers. The largest shielding factor measured was 6×106 for a nested set of three shields.

References:

E.A. Donley, E. Hodby, L. Hollberg, and J. Kitching, Demonstration of high-performance compact magnetic shields for chip-scale atomic devices, Rev. Sci. Instrum. 78, 083102 (2007)