HR: 11:05h
AN: GP22A-04    [Abstracts]
TI: Directional Behavior of Remanent Magnetization at Low Temperatures Measured With a New SQUID Magnetometer Probe
AU: * Smirnov, A V
EM: alexei@earth.rochester.edu
AF: Department of Earth and Environmental Sciences, University of Rochester Hutchison Hall 227, Rochester, NY 14627 United States
AU: Tarduno, J A
EM: john@earth.rochester.edu
AF: Department of Earth and Environmental Sciences, University of Rochester Hutchison Hall 227, Rochester, NY 14627 United States
AU: Goree, W S
EM: billgoree@earthlink.net
AF: William S. Goree Inc., 2040 Sunset Drive, Pacific Grove, CA 93950 United States
AB: Many magnetic minerals undergo magnetic transitions at low temperatures. In magnetite, such a transition (the Verwey transition) occurs at $\sim$120 K. A loss of remanence at the Verwey transition is thought to be preferentially associated with large multidomain grains. Because these grains often carry secondary magnetizations, low temperature treatments are gaining popularity as an additional means of magnetic cleaning, used to isolate primary magnetizations. Smaller grains also lose some remanence, but part of this remanence (known as the low-temperature ``magnetic memory'') restores after warming. However, our understanding of the magnetic memory and other processes in magnetic minerals at low temperatures is based almost entirely on total moment measurements (rather than directional data). The assumption has been that these total moment data adequately mimic the behavior of directions. We examined this assumption using a prototype of a new device enabling the measurement of remanence directions at low temperatures using a 2G Enterprises 3-component SQUID magnetometer. Surprisingly, we found that remanence directions carried by magnetite after cycling to low temperatures (in a zero field environment) do not always coincide with the original magnetization. We discuss possible mechanisms which may result in such a deviation, as well as continuing efforts to develop the low temperature probe.
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting