Electron-Spin Resonance of ${\mathrm{K}}_2$Zn${\mathrm{F}}_4$: ${\mathrm{Mn}}^{2+}$

Electron-spin-resonance (ESR) measurements at 24 GHz have been made on single crystals of ${\mathrm{K}}_2$Zn${\mathrm{F}}_4$ doped with Mn. The spectra obtained in these measurements correspond to ${\mathrm{Mn}}^{2+}$ in the ${\mathrm{Zn}}^{2+}$ sites (point group $\frac{4}{\mathrm{mmm}}$)) in this material. The measured values of the spin-Hamiltonian parameters corresponding to the fine and hyperfine structure are $g_{\parallel }=2.0030\mathrm{}$, $g_{\perp }=2.0028\mathrm{}$, $A=-88.7\mathrm{}\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $B=-89.3\mathrm{}\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $D=36.0\mathrm{}\times {10}^4$ ${\mathrm{cm}}^{-1\mathrm{}}$, $a=5.6\mathrm{}\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, and $F=1.9\mathrm{}\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. In addition, the transferred hyperfine parameters were obtained from the ESR measurements. The measured values of these parameters, which result from interactions between the ${\mathrm{Mn}}^{2+}$ $3d$ electrons and ${\mathrm{F}}^{-}$ and which refer to the four equivalent nearest-neighbor ${\mathrm{F}}^{-}$ ions in the (001) plane (type I) and the two equivalent nearest-neighbor ${\mathrm{F}}^{-}$ ions along the forfold axis (type II), are $A_s^{\mathrm{I}}=18.1\mathrm{}$, $A_s^{\mathrm{II}}=14.9\mathrm{}$, $A_{\sigma }^{\mathrm{I}}0.4$, $A_{\sigma }^{\mathrm{II}}-\frac{1}{2}{A}_{\pi }^{\mathrm{II}}=0.3\mathrm{}$, and