Electron-Spin Resonance ofCr3+in Gallium Alums. I

The electron-spin resonance of ${\mathrm{Cr}}^{3+}$ impurities in Rb Ga${\left(\mathrm{S}{\mathrm{O}}_4\right)}_2$·12${\mathrm{H}}_2$O, CsGa${\left(\mathrm{S}{\mathrm{O}}_4\right)}_2$·12${\mathrm{H}}_2$O, and the deuterated forms of these alums was studied at 300 and 4.2°K. Four magnetic complexes exhibiting trigonal symmetry were found in each crystal and the results were fitted to a suitable spin Hamiltonian giving the $g$ and $D$ parameters. The magnitude of the $D$ parameter decreased by about 38% in the Rb alums and by only 8% in the Cs alums. Moreover, the $D$ parameter had opposite signs in the Rb and Cs alums. The effect of deuteration did not produce any significant changes from the case of the hydrated alums. It seems probable that the size of the monovalent ion can affect the positions of the other ions in the unit cell of alum, which in turn can affect the chromium magnetic complexes.