Single crystals of CaO doped with ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ have been investigated by paramagnetic resonance at 9.5 kMc/sec. Both ions are found to go in substitutionally for the ${\mathrm{Ca}}^{2+}$ ion. The spectrum of each can be described by a spin Hamiltonian for an ion in a cubic field. The parameters determined for ${\mathrm{Mn}}^{2+}$ are $g=2.0009\mathrm{}\pm 0.0005$, $a=(5.9\mathrm{}\pm 0.3)\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$ and $A=(-80.8\mathrm{}\pm 0.2)\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. The ${\mathrm{Fe}}^{3+}$ parameters are $g=2.0052\mathrm{}\pm 0.0005$ and $a=(63.8\mathrm{}\pm 0.3)\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$. The results are discussed in relationship to the Powell, Gabriel, and Johnston theory of the ground-state splitting of ${\mathrm{Mn}}^{2+}$ by cubic crystalline fields.

• Received 18 April 1962

DOI:https://doi.org/10.1103/PhysRev.127.1529