Scanning superconducting quantum interference device susceptometry

We report a scanning superconducting quantum interference device (SQUID) microsusceptometer with a spatial resolution of 8 mum, tested by measuring the susceptibility of individual 3 mum diam tin disks. Images of the disks agree well with numerical modeling based on the known geometry of the SQUID microsusceptometers. The low-field spin sensitivity between 1.5 and 6 K is 1x10(5) mu (B)/root Hz while scanning. (C) 2001 American Institute of Physics.