1. Department of Electrical and Computer Engineering University of Minnesota Kenneth H. Keller Hall, 200 Union St. SE Minneapolis MN 55455 USA
2. Lake Shore Cryotronics Inc. Westerville OH 43082 USA
3. Institute for Rock Magnetism Department of Earth and Environmental Sciences University of Minnesota 150 John T. Tate Hall, 116 Church St. SE Minneapolis MN 55455 USA
4. Department of Chemical Engineering and Material Science University of Minnesota 421 Washington Ave. SE Minneapolis MN 55455 USA