Design and performance analysis of three superconducting magnetic sensors for the measurement of small fields

We analyse here the sensing performance of a magnetometer which is based on the linear dc-field dependence of the second harmonic signal generated by high-T-c polycrystalline superconductors. Experiments realized in a series of polycrystalline REBa2Cu3O7-delta (RE = Y, Sm and Nd) superconductors have shown that some parameters (e.g. H-c1J and H*) peculiar to the studied superconductors change depending on the RE ions, and those determine the sensitivity limit of the magnetometer. The lowest measurable magnetic fields are 0.1, 5 and 38 nT for RE = Sm, Y and Nd, respectively at the functioning temperature of 77 K. With an upper limit above the Earth's field the magnetometer has attracted the attention of manufacturers in the industry.