Superhyperfine Structure of the EPR Spectra of Nd3+ Impurity Ions in Fluorite CaF2

EPR spectra of a CaF 2 single crystal that was grown from melt containing a small addition of NdF 3 were studied. Signals corresponding to tetragonal centers of Nd 3+ ions and cubic centers of Er3+ and Yb3+ ions were found. Superhyperfine structure (SHFS) in the spectra of the Nd 3+ ions was observed for the first time in this crystal; parameters of the superhyperfine interaction of the Nd 3+ ions with the nearest nine fluorine ions were determined. The dependence of the resolution of the Nd 3+ EPR spectrum SHFS on the incident microwave power at the temperature of T ≈ 6 K was studied. Obtained results are discussed and compared with the literature data.