EPR of trivalent iron centers in a BaF2: Fe crystal

An orthorhombic paramagnetic Fe3+ ion center (concentration of iron ions is 0.1 at. %) was found using EPR in BaF2: Fe crystals irradiated by x rays. The EPR spectra recorded in the Q range at a temperature T = 77 K exhibit both the fine structure typical of a center with effective spin S = 5/2 and a superhyperfine structure (SHFS) indicating the SHFS interaction of the electronic moment of the center with the nuclear magnetic moments of its six ligands (F− ions). An analysis of the SHFS reveals that this center forms through the replacement of a Ba2+ cation by a Fe2+ cation, which transforms into a Fe3+ (6 A 1g ) cation under x-ray irradiation and shifts into a neutral position along the C2 axis of the cubic coordination shell of the replaced host cation.

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