We have been developing a new high sensitivity magnetometer for paleomagnetic applications, the low-transition temperature SQUID Microscope. This magnetometer, originally designed for biomagnetic studies by F. Baudenbacher (Vanderbilt University), maps the vertical component of the magnetic field above room-temperature geologic samples with ~1,000 times better moment resolution and ~100 times better spatial resolution than existing superconducting rock magnetometers. This allows us to directly map the three components of the magnetic field of individual grains and textures in thin sections. Over the last decade, we have continued to expand the capability of SQUID microscopy. We have developed inversion techniques that use SQUID microscope field measurements to constrain the magnetization distribution within samples. We have used SQUID microscopy to adapt standard paleomagnetic techniques like thermal and alternating field demagnetization, paleointensity methods, conglomerate tests, isothermal and anhysteretic remanent magnetization acquisition, magnetic anisotropy analyses, and even magnetostratigraphy to microscale samples.
Key publications by our group:
Oda, H., A. Usui, I. Miyagi, M. Joshima, B. P. Weiss, C. Schantz, L. E. Fong, K. K. McBride, R. Harder, F. J. Baudenbacher (2011) Ultrafine-scale magnetostratigraphy of marine ferromanganese crust, Geology, 39, 227-230 / link /
Gattacceca, J., M. Boustie, E. Lima, B. P. Weiss, T. de Resseguier, J.-P. Cuq-Lelandais (2010) Unraveling the simultaneous shock magnetization and demagnetization of rocks, Phys. Earth Planet. Inter., 182, 42-49 / link /
Lima, E. A. and B. P. Weiss (2009) Obtaining vector magnetic field maps from single-component measurements, J. Geophys. Res., 114, B06102, doi:10.1029/2008JB006006 / link / / supplementary information /
Weiss, B. P., L. E. Fong, H. Vali, E. A. Lima, F. J. Baudenbacher (2008) Paleointensity of the ancient Martian magnetic field, Geophys. Res. Lett., 35, L23207, doi:10.1029/2008GL035585 / link /
Weiss, B. P., E. A. Lima, L. E. Fong, F. J. Baudenbacher (2007) Paleointensity of the Earth's magnetic field using SQUID microscopy, Earth Planet. Sci. Lett., 264, 61-71 / link /
Weiss, B. P., E. A. Lima, L. E. Fong, F. J. Baudenbacher (2007) Paleomagnetic analysis using SQUID microscopy, J. Geophys. Res.,112, B09105, doi:10.1029/2007JB004940 / link /
Gattacceca, J., M. Boustie, B. P. Weiss, P. Rochette, E. A. Lima, L. E. Fong, F. Baudenbacher (2006) Investigating impact demagnetization through laser impacts and SQUID microscopy, Geology, 34, 333-336 / link / / supplementary information /
Weiss, B. P., H. Vali, F. J. Baudenbacher, J. L. Kirschvink, S. T. Stewart, D. L. Shuster (2002) Records of an ancient Martian magnetic field in ALH84001, Earth Planet. Sci. Lett., 201, 449-464 / link /
Weiss, B. P., J. L. Kirschvink, F. J. Baudenbacher, H. Vali, N. T. Peters, F. A. Macdonald, and J. P. Wikswo (2000) A low temperature transfer of ALH84001 from Mars to Earth, Science, 290, 791-795 / link /
// Closeup of SQUID Microscope sensor, with Franz and ALH84001 for scale
// Inside the SQUID Microscope: the bare SQUID sensor mounted on the end of the 4 K cold finger surrounded by vacuum space
// One of our high resolution bare SQUID sensors. Shown is the SQUID loop (light blue square at center), Josephson junctions (two red rectangles on left side of SQUID loop), integrated feedback and modulation coil (brown horseshoe wire on right side of SQUID), feedback circuit pads (top and bottom large yellow pyramids), and bias current pads (right and left large yellow pyramids). The diameter of the hole in the center of the SQUID loop is 40 microns.
// SQUID microscope image of the vertical component of the magnetic field above a basalt disk that had been laser shocked at shown locations. Shock demagnetization is evident at these locations.”
// SQUID microscope image of the vertical component of the field above a transect taken perpendicularly to the sedimentary layers of a ferromanganese crust from the ocean floor. Multiple geomagnetic reversals are evident.