Scanning SQUID Microscope

摘要

For nondestructive evaluations of magnetic microstructures, the SQUID microscope becomes a powerful tool [1]. The SQUID should be positioned as close as possible to the sample to achieve a high spatial resolution. Recently, SQUID microscopes using a high permeability probe as a flux guide have been developed measuring a sample in air at room temperature [2-7]. The sharp probe makes it possible to detect the magnetic field from a localized area by bringing the tip close to the sample. We have developed a high T_c SQUID probe microscope with a high permeability probe. We have obtained a magnetic image with spatial resolution of a micrometer [7]. Until now, the samples were made to approach the probe as close as possible, with care to avoid contact by viewing through an optical microscope. However this method is not preferable because the sample surface is not necessarily smooth. To achieve higher spatial resolution, distance from the sample surface to the probe tip should be measured with higher resolution up to nanometer range.