Influence of high pressure on the luminescence transitions of Mn4+-doped gadolinium gallium garnet

We present results of a high-pressure photoluminescence study of Mn- and Ca-doped gadolinium gallium garnet (GGG) crystals. Since the Mn4+ ion has the same electronic structure of the open 3d(3) shell as Cr3+, its spectroscopic properties are expected to be similar to those of the Cr-doped GGG. We observed the luminescence R-lines of various Mn4+ centres in GGG. In the 0-118 kbar pressure range those R-lines shift linearly to lower energies. The pressure coefficients are of the order of 2 cm(-1) kbar(-1), about three times larger than that for Cr3+ ions. This fact can be explained by different strength of coupling of isoelectronic Cr3+ and Mn4+ ions with GGG host. The changes of the radiative decay times of the Mn4+ centres as a function of pressure are fitted with a theoretical model.