1999 Summer Research Faculty-Student Team

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Dr. Steven Ratliff and Jeffrey Wallhoff

Steven Ratliff is a Physics professor at Northwestern College.
Jeff is a Pre-engineering major in his second year at Northwestern College.

Wide Temperature Range AC Susceptometer
Steven T. Ratliff and Jeffrey Wallhoff
Northwestern College

E. Dan Dahlberg
Department of Physics, University of Minnesota

An alternating current (AC) susceptometer was constructed. The device will measure the magnetic susceptibility of small (approximately 2 mm x 2 mm x 1 mm) samples from 4 K up to room temperature. The device was built to fit inside a glass dewar, and can be cooled with liquid nitrogen or liquid helium. Magnetic field coils were also constructed, so that the sample can be subjected to a steady magnetic field. A computer data acquisition system is used to collect the data from the susceptometer. The device was tested using well-known materials of high purity (Dysprosium Oxide and Gadolinium Oxide). It was used to obtain a new result on a two-layer thin film sample (15 Angstroms of Cobalt Oxide on top of 1000 Angstroms of Permalloy on a substrate). The sample was cooled from room temperature in a magnetic field. The magnetic field was then turned off and varied from 0 Gauss to 142 Gauss. A peak at approximately 22 Gauss was observed.