Comment on ‘‘Optical and electron paramagnetic resonance studies of Fe impurities in yttrium aluminum garnet crystals’’

In this paper, we examine the relative concentrations of ${\mathrm{Fe}}^{+2\mathrm{}}$ and ${\mathrm{Fe}}^{+3\mathrm{}}$ in yttrium aluminum garnet and their distribution between octahedral and tetrahedral sites. We suggest that by examining the tetrahedral iron absorption peaks at 407 and 415 nm, the hypothesis of substantial shifting of ${\mathrm{Fe}}^{+3\mathrm{}}$ from tetrahedral to octahedral sites when annealed between 600 to 1100 °C and the conversion of substantial amounts of ${\mathrm{Fe}}^{+3\mathrm{}}$ to ${\mathrm{Fe}}^{+2\mathrm{}}$ when annealed in a reducing atmosphere can be analyzed.