Fine Structure in Electron Paramagnetic Resonance ofMn2+in Zinc Sulfate

The electron spin resonance of 0.01% ${\mathrm{Mn}}^{2+}$ in single crystals of ZnS${\mathrm{O}}_4$ has been studied in order to investigate the crystal-field interaction, which may be representative of the single-ion anisotropy in MnS${\mathrm{O}}_4$. The symmetry group for the zinc site, which the ${\mathrm{Mn}}^{2+}$ ions are assumed to occupy, is $C_i$. There are, in general, four inequivalent zinc sites which produce a spectrum of 320 possible lines at an arbitrary orientation. However, data have been taken with $H_0$ in symmetry planes of the crystal so that pairs of inequivalent sites become equivalent. This results in some simplification of the spectrum and provides a method for accurate alignment of the crystal. The spectrum has been fitted to a low-symmetry spin Hamiltonian. Since crystal-field terms are large, perturbation theory could not be used, and the spin-Hamiltonian analysis of the spectrum was accomplished by computer programs that diagonalize the spin-Hamiltonian matrix. An isotropic $g$ factor of 2.0017±0.0010 and spin-Hamiltonian parameters $C_{20}=(3.792\mathrm{}\pm 0.001)\times {10}^{-2\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $C_{21}=(3.815\mathrm{}\pm 0.001)\times {10}^{-2\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $C_{22}=(5.808\mathrm{}\pm 0.001)\times {10}^{-2\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$ with lobe orientations ${\lambda }_{21}=152.6\mathrm{}°$ and ${\lambda }_{22}=86.5\mathrm{}°$ describe the room-temperature spectrum reasonably well. The inclusion of the $C_{4q}$ terms improves the fit.