Determination of magnetic properties using a room-temperature scanning SQUID microscope

We have used a YBCO de SQUID at 77 K to image room-temperature magnetic thin film samples. Samples imaged include Fe/sub 3/O/sub 4/, rare earth magnets such as samarium cobalt, and CMR materials. We typically saturate the magnetization of the sample in fields up to 8.5 Tesla, and then image the remanent (zero applied field) state. To help quickly interpret and quantify the SQUID microscope data, we have developed several analytical techniques. These techniques yield quantifiable results of magnetic properties, including magnetization, total dipole moment, and the demagnetizing field. We will present our results and discuss applications and limits of SQUID microscopy to the characterization of bulk and thin-film magnetic materials.