ZERO-FIELD SPIN-LATTICE RELAXATION OF CR3+ ION IN RUBY

The spin-lattice relaxation time T1 of the Cr3+ ion in the Al2O3 lattice has been measured in zero magnetic field. The theoretical value of T1 in this particularly simple case is shown to agree well with the measured value for all types of crystal growth at low Cr3+ concentration. The anomalous concentration dependence observed in the range 0·02-0·1% Cr3+ for all samples except those grown by the vapour phase modification of the Verneuil process is ascribed to the inhomogeneous Cr3+ ion distribution in most crystals.