New photoluminescence phenomena in milled MnF2 at high pressure

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 alpha-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.