Abstract
Precise photoluminescence measurements have been carried out on RbCdF3:Mn2+ in the 9-300 K range to explore the structural phase transition of the host lattice at Tc=124 K using the first (M1) and second (M2) moments of the emission band together with the lifetime tau as probes. Aside from showing a sensitivity of M2(T) and tau (T) to the phase transition, the present data reveal that the curve M1(T) experiences a small but observable change of slope in the vicinity of Tc. It is demonstrated that this jump, Delta t( delta M1/ delta T)P=0.22 cm-1 K-1, is mainly associated with the increase experienced by the local thermal expansion coefficient below Tc. The importance of both the implicit and explicit contributions to M1(T) is analysed throughout this work. Neither the luminescence nor the excitation spectrum shows any evidence of tetragonal distortion in the MnF64- complex. This fact is explained through the Rax-Req=0 2 pm value (where Rax and Req are the axial and equatorial Mn2+-F- distances) at 30 K, and the coupling coefficient VE=66 cm-1 pm-1 with the Eg Jahn-Teller mode of MnF64-. Finally, we have found that this crystal exhibits photochemical reactions under UV light irradiation, leading to the formation of centres that transfer easily to Mn2+ ions. These centres give rise to an intense absorption band at 310 nm, analogously to those previously formed under x-irradiation.
Published Version
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