Experimental and theoretical studies of the ${\mathrm{Nd}}^{3+}$ spectrum in yttrium aluminum garnet are reported in the present article. From the crystal-field calculations on various $J$ manifolds, it is concluded that the crystal field is approximately tetragonal. The agreement between observed and calculated splitting patterns for $J$ manifolds in which $J$ mixing is small is satisfactory. Our best evaluation of the crystal-field parameters yields: ${A_2}^0=270\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${A_4}^0=-250\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${A_4}^4=1250\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, ${A_6}^0=92\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$, and ${A_6}^4=-965\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$.

• Received 1 June 1964

DOI:https://doi.org/10.1103/PhysRev.136.A711