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

Abstract

Results of EPR measurements of Cr³⁺ in K₂ZnF₄ are reported for crystals co-doped with Na⁺ or Li⁺ ions. A few kinds of Cr³⁺ centres are observed in both crystals, where parts of Cr³⁺ are associated with charge compensators. In Na⁺-doped crystal, the nearest Zn²⁺-vacancy centre has comparable intensity with the uncompensated centre, but the nearest K⁺-vacancy centre is not observed. In Li⁺-doped crystal, the Zn²⁺-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 Cr³⁺ associated with Li⁺ at the nearest Zn²⁺ 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.