Optical and EPR studies of the Er3+ion site distribution in SrLaAlO4crystals

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 resoance (EPR) detect two distinct quasi-centres in this materils. At concentrations up to 0.1%, a single centre of C4v symmetry is present which comparieses an isolated Er3+ion. At higher concentrations, an orthorhombic pair centre is also detected. The measured g-values for these centres are g⊥ = 8.5 ± 0.05 and g⊥ = 2.7 ± 0.05, and gx = 9.4 ± 0.05, gy = 6.8 ± 0.05 and gz = 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.