Luminescence of Exchange Coupled Pairs of Transition Metal Ions

Authors:
  • AMA. Meijerink
    A. Meijerink
Publisher website
Google Scholar
Abstract
The influence of exchange interaction between paramagnetic ions on the luminescence properties is investigated for Mn2+­Mn2+,Mn2+­Mn2+, Cr3+­Cr3+,Cr3+­Cr3+, Cr3+­Gd3+,Cr3+­Gd3+, and Mn2+­Gd3+Mn2+­Gd3+ pairs. Two effects are reported: shortening of the lifetime of the spin-forbidden emission and a shift of emission lines or bands to a longer wavelength. The shortening of the lifetime of the spin-forbidden emission is important in Mn2+Mn2+ doped phosphors. For application of Mn2+Mn2+ -doped phosphors in displays the long lifetime of the Mn2+Mn2+ emission is a problem. Shortening of the lifetime is possible by exchange coupling with Mn2+Mn2+ neighbors, or possibly other paramagnetic neighbors. The results reported here show that the lifetime shortening depends on the exchange-coupling parameter J. The strongest coupling is observed in Cr3+­Cr3+Cr3+­Cr3+ pairs and the lifetime shortening is strong (e.g., in LaAlO3:Cr3+LaAlO3:Cr3+ J=63 cm−1J=63 cm−1 and the lifetime is about 30 times shorter for the pair emission). The coupling in Mn2+­Mn2+Mn2+­Mn2+ and Cr3+­Gd3+Cr3+­Gd3+ pairs is weak. Typically, values for J are around 1 cm−1 and the lifetime is reduced by a factor of 2-10 (e.g., J is −1.0 cm−1 for exchange coupling between Cr3+Cr3+ and Gd3+;Gd3+; the lifetime of the spin-forbidden Cr3+Cr3+ emission is 14 ms in GdAlO3GdAlO3 compared to 56 ms in LaAlO3).LaAlO3). The lifetime shortening for the Mn2+Mn2+ emission is not related to the observed red shift for the pair emission. For the Mn2+­Gd3+Mn2+­Gd3+ pair the exchange interaction is very weak and no significant lifetime shortening could be measured for Gd3+­Mn2+Gd3+­Mn2+ pairs (24 ms for the Mn2+Mn2+ emission in YF3YF3 vs. 22 ms in GdF3).GdF3). © 2001 The Electrochemical Society. All rights reserved.

This publication has 19 references indexed in Scilit: