Broadband EPR Spectroscopy of the Ground Electron State of the Fe4+ Impurity Ion in Amethyst

Fine structure of ground electron state of Fe4+ impurity ion in a natural amethyst crystal was studied by broadband electron paramagnetic resonance spectroscopy in the frequency range of 34–500 GHz. It is established that energy levels scheme consists of ground quasi-doublet Sz = ± 2, quasi-doublet S z= ± 1 and singlet Sz=0 with zero-field energies ± 4.9 GHz, 435.2 ± 45.4 GHz and 584 GHz, respectively. Parameters of effective spin Hamiltonian describing dependences of electron spin levels on magnetic field are determined.