Energy transfer and luminescence inRbMnxMg1−xF3

Abstract

An investigation, directed toward an understanding of the concentration-dependent characteristics of Mn-Mn energy transfer, has been carried out in $\mathrm{Rb}{\mathrm{Mn}}_x{\mathrm{Mg}}_{1-x}{\mathrm{F}}_3$ via a detailed luminescence study from 4 to 120 K. The emission of $\mathrm{Rb}{\mathrm{Mn}}_x{\mathrm{Mg}}_{1-x}{\mathrm{F}}_3$ down to a 40 at.% ${\mathrm{Mn}}^{2+}$ concentration consists of two distinct ${\mathrm{Mn}}^{2+}$ bands which are featureless except in the case of the stoichiometric system. The bands are attributed to two localized traps positioned below the lowest excited level of ${\mathrm{Mn}}^{2+}$. The variation of the spectra and of the decay patterns with temperature indicate a "boil-off" mode of decay for the shallower trap and nonradiative decay to the ground state for the deeper trap. The details of the kinetics have allowed us to calculate the rate of energy transfer to the shallower luminescence trap for the various samples. It can be concluded that an efficient non-diffusion-limited transfer of excitation exists in $\mathrm{Rb}{\mathrm{Mn}}_x{\mathrm{Mg}}_{1-x}{\mathrm{F}}_3$ down to at least a 40 at.% ${\mathrm{Mn}}^{2+}$ concentration. Indirect trap-to-trap transfer, present in RbMn${\mathrm{F}}_3$, is not probable in the nonstoichiometric samples due to the increased presence of quenching sites.