Sign and magnitude of spin Hamiltonian parameters for Mn²⁺ impurities in calcite. A multi- and low-frequency EPR study

Abstract

L-, S-, and X-band powder EPR spectra and an L-band single-crystal spectrum of Mn²⁺ impurities in calcite were analysed by the fitting of full spectral traces to a theoretical model. This analysis gives as parameters the traditional spin Hamiltonian parameters reflecting the three-fold symmetry of the cation lattice site as well as parameters determining the band shape and width of the resonances. The three frequencies give a consistent description of the system. For this spin system it is shown that the relative sign of the axial zero-field splitting parameter Dand the hyperfine coupling constant A may be safely determined at the L-band.

Keywords:

• EPR spectroscopy
• Calcite
• Dolomite
• Marble
• Spin

Acknowledgements

We thank the EPSRC EPR National Service at the University of Manchester for use of the spectrometers. We are grateful to Ole Johnsen, National Geological Museum, Copenhagen, for providing the high-quality calcite crystal used for the 3 GHZ single-crystal experiment.