Optical and EPR studies of the Er3+ ion site distribution in SrLaAlO4 crystals

We report on a spectroscopic investigation of SrLaAlO4 crystals doped with 0.01., 0.1 and 1 molar percent of Er3+. Both laser selective excitation and electron paramagnetic resonance (EPR) detect two distinct quasi-centres in this materials. At concentrations up to 0.1%, a single centre of C-4v symm etry is present which comprises an isolated Er(3+)ion. At higher concentrat ions, an orthorhombic pair centre is also detected. The measured g-values f or these centres are g(perpendicular to) = 8.5 +/- 0.05 and g(parallel to) = 2.7 +/- 0.05, and g(x) = 9.4 +/- 0.05, g(y) = 6.8 +/- 0.05 and g(z) = 2.3 +/- 0.05, respectively. The large inhomogeneous broadening of the optical and EPR spectra is attributed to compositional disordering of Sr2+ and La3 ions, prevalent in the host lattice.