A scanning SQUID microscope for samples at room temperature

We report on the development of a scanning SQUID microscope for measurements of samples at room temperature. A thin film niobium DC-SQUID is used with conventional read-out electronics. It is placed above the thin bottom window of a fiberglass cryostat, allowing us to realize a distance of about 75 /spl mu/m between SQUID and sample. The evaporation rate for the liquid helium was about 0.3 1/h. Because the effective SQUID area can easily be brought below 10 /spl mu/m/sup 2/, the obtainable spatial resolution of such a scanning SQUID microscope is limited mainly by the distance between SQUID and sample. The sample is moved under the cryostat with a computer controlled XY-stage. Provisions are made for quick sample changes which are important for the practical application of such a device.