OPTICAL AND ELECTRON-SPIN-RESONANCE SPECTROSCOPY OF TI3-DOPED YTTRIUMAND GADOLINIUM ALUMINOBORATES()

Single crystals of Ti3+-doped aluminoborates YAl3(BO3)(4) (YAB) and Gd Al3(BO3)(4) (GAB) have been grown by the top-seeded solution growth te chnique, and the optical absorption, photoluminescence and electron sp in resonance (ESR) properties of Ti3+ dopants measured at low temperat ure. The optical absorption spectrum of Ti3+ comprises two broad bands with peaks at 514 and 576 nm in YAB and at 520 and 586 nm in GAB. The energy separation of the two bands in each crystal is due to the stat ic Jahn-Teller splitting of the excited (2)E State of the Ti3+ ions. P hotoluminescence from excited Ti3+ ions occurs as a broad band in the near-infrared region with a peak at lambda = 747 nm in YAB and 754 nm in GAB when measured at 14 K. Both absorption and photoluminescence sp ectra are strongly polarized. The spin Hamiltonian parameters for Ti3 ions substituting at trigonally symmetric Al3+ sites in YAB have been determined from the orientation dependence of the ESR spectra. The me asured shifts in the components of the g-tensor from the free electron g-value of 2.0023 are interpreted in terms of the mixing of the highe r component of the T-2(2) ground states and of the (2)E excited state into the lowest T-2(2) ground state by spin-orbit interaction.