HR: 0830h
AN: GP31B-0751    [PDF]
TI: FORC Diagrams of Synthetic Magnetic Minerals at Ambient and High Temperatures
AU: * Roth, A L
EM: alroth@geology.ucdavis.edu
AF: University of California Davis, One Shields Ave, Davis, CA 95616 United States
AU: Verosub, K L
EM: verosub@geology.ucdaavis.edu
AF: University of California Davis, One Shields Ave, Davis, CA 95616 United States
AU: Pike, C R
EM: christopherpike@lycos.com
AF: University of California Davis, One Shields Ave, Davis, CA 95616 United States
AU: Acton, G
EM: acton@geology.ucdavis.edu
AF: University of California Davis, One Shields Ave, Davis, CA 95616 United States
AB: FORC diagrams provide a new tool for probing the magnetic structure of natural and synthetic materials. In order to interpret the FORC diagrams of natural samples properly, diagrams for well-characterized synthetic samples must be cataloged. We have obtained FORC diagrams for synthetic samples of pure magnetite, hematite, maghemite, goethite and pyrrhotite, each of which was also studied using M\"ossbauer spectroscopy. The FORC diagram for each mineral has distinct features that can form the basis for magnetic mineral identification. However, due to the large saturation magnetization of magnetite, even a small impurity of that mineral in a sample leads to its dominance in the FORC diagram. Traditionally, heating of samples above the Curie temperature of magnetite (580$\deg$C) has been used to detect the presence of hematite in mineralogically mixed systems. We have found that for mixtures of magnetite and hematite, FORC diagrams obtained above the Curie point for magnetite can not only detect the presence of hematite but can provide information about its grain-size distribution and about magnetic interactions as well
DE: 1519 Magnetic mineralogy and petrology
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting