Thermal Properties of Red Zero-Phonon Luminescence Line from Mn2+ Ions in Oxide Crystals

Abstract

Temperature dependence of emission properties of sharp, zero-phonon line (ZPL) associated with 4T1g →6A1g transition of Mn2+ ions doped in LiMgPO4 is studied, together with the Mn2+-concentration dependence. The ZPL is observed at 611.8 nm at temperatures below 120 K. The intensity relative to the intensity of superimposed phonon sidebands is increased in proportion to T2 with increasing temperature from 18 K. The peak energy and full width at half maximum (FWHM) are increased in proportion to coth 1/2 (hν/2kBT). Unlike the phonon sideband emission which shows single exponential decay and decrease of decay time with increase of temperature, the ZPL emission has the fast and slow decay components and shows temperature-independent decay times. A blue shift of the ZPL peak energy is observed with increase of Mn2+ concentration x doped in LiMg1−x Mn x PO4 from 0.0015 to 0.0050 at 18 K, while a broadening of line width is observed with increase of the concentration. Each of the peak energy and FWHM is approximated by a quadratic equation in the form a+bx+cx 2. It is suggested that these results are understood by the interaction of the excited 4T1g state with phonons and crystal field, from comparison with the theoretically expected formulae.