High–Resolution Magnetic Field Measurement Using an STM–SQUID

We have developed an STM–SQUID microscope that combined a scanning tunneling microscope (STM) and a SQUID probe microscope for the purpose of high–resolution magnetic field measurement. We were able to obtain a spatial resolution of 1 μm or less by polishing the tip of the needle on the SQUID probe microscope to 100 nm or less, and by using a magnetic probe, which was the flux guide, as the STM probe. In this study, we took magnetic images of typical ferromagnetic materials, such as bulk iron and bulk nickel using the STM–SQUID microscope. We successfully observed the magnetic domain structures of these magnetic materials. However, topographic artifacts were also observed in the STM–SQUID images due to the background magnetic field from the sample. The future subject for resolution and quality improvement became clear.