EPR of Cr3+ Centres in K2ZnF4 Crystals Doped with Na+ and Li+ Ions

Results of EPR measurements of Cr 3+ in K 2 ZnF 4 are reported for crystals co-doped with Na + or Li + ions. A few kinds of Cr 3+ centres are observed in both crystals, where parts of Cr 3+ are associated with charge compensators. In Na + -doped crystal, the nearest Zn 2+ -vacancy centre has comparable intensity with the uncompensated centre, but the nearest K + -vacancy centre is not observed. In Li + -doped crystal, the Zn 2+ -vacancy centre is weak compared with the uncompensated centre, and the K + -vacancy centre is also not observed, but a new centre having comparable intensity with the uncompensated centre appears. The new centre is attributed to Cr 3+ associated with Li + at the nearest Zn 2+ site. Fine structure parameters in the spin Hamiltonian are discussed by superposition of the two uniaxial terms along the crystal-tetragonal axis and bond axis to the charge compensator.