HR: 0830h
AN: GP11B-0260    [PDF]
TI: Electron Paramagnetic Resonance Spectroscopy: Magnetic Method vs Analytical Technique
AU: * Gehring, A U
EM: gehring@sl.ethz.ch
AF: Andreas U. GEHRING, Institute of Geophysics ETH Zurich, Zurich, 8093 Switzerland
AU: Weidler, P G
EM:
AF: Peter G. Wei9dler, Forschungszentrum Karlsruhe ITC-WGT, Karlsruhe, 76021 Germany
AB: Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool to study molecules and materials containing unpaired electrons in magnetic fields at which they come into resonance with monochromatic radiation. Magnetic fields of about 0.3 Tesla (T) correspond to resonance with an electromagnetic field of frequency 10 GHz and wavelength 3 cm (X-band of the microwave (mw) region of electromagnetic spectrum). An EPR spectrum can be described by the g-value, the hyperfine coupling constant A, and the line width as well as line shape. The g-value gives information about the electronic structure and A about the ligand field of a paramagnetic species. Microwave radiation absorption by magnetic minerals is referred to as ferromagnetic resonance (FMR). The EPR absorption peak due to ferromagnetics can be orders of magnitude more intense than peaks due to paramagnetics. In natural samples ferromagnetic impurities such as coatings or inclusions can produce usually broad spectra which superpose paramagnetic signals of interests. As example, an $\alpha$-FeOOH-$\gamma$-Fe$_{2}$O$_{3}$-$\alpha$-Fe$_{2}$O$_{3}$-system is presented to demonstrate the potential EPR spectroscopy to analyze magnetic phases. The results exhibit that EPR is very sensitive to detect magnetic phases, but for the detailed identification and characterization complementary tools such as classical rock magnetic techniques or X-ray diffraction are mandatory.
DE: 1519 Magnetic mineralogy and petrology
DE: 1540 Rock and mineral magnetism
DE: 1599 General or miscellaneous
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting