Evaluation of flux guide performance in a SQUID microscope

Abstract

We have developed a high-TC scanning SQUID microscope. In order to improve its spatial resolution a permalloy needle was used as a flux guide. The flux guide makes it possible to measure samples in air at room temperature. The magnetic field pattern of printed characters with linewidth of the order 100 µm was imaged well. We have investigated the performance of the flux guide both experimentally and numerically. The expected line scan image of a meander line structure was calculated using the three-dimensional finite element method and was found to agree reasonably well with the experimental data.