New photoluminescence phenomena in milled MnF₂ at high pressure

Abstract

This work presents a time-resolved spectroscopic study of MnF₂ as grown and milled into nanoparticles. We find that high pressure (HP) induces photoluminescence (PL) at room temperature (RT) above 13 GPa in MnF₂ single crystals. RT-PL occurs as a consequence of the inhibition of excitation migration processes among Mn²⁺ ions resulting from the HP-induced structural phase transition (SPT) to the α-PbCl₂-type phase. This SPT involves important changes in the Mn– F– Mn exchange paths yielding radiative de-excitation in Mn²⁺, and thus also PL. As a salient result, we have found an increase of the PL-quenching temperature in nanosized milled MnF₂.

Keywords:

• Photoluminescence
• High pressure
• Nanoparticles
• MnF₂
• Time-resolved spectroscopy
• Phase transition

Acknowledgements

Financial support from the Spanish MEC (Project No. MAT2005-00099) is acknowledged. Dr. Hernández thanks the Research Intensification Program I3 of the University of Cantabria for a research contract.