Photoproduction of long-lived holes and electronic processes in intrinsic electric fields seen through photoinduced absorption and dichroism in Ca₃Ga_2 xMn_xGe₃O₁₂garnets

Abstract

Abst ractLong-lived photoinduced absorption and dichroism in the Ca 3 Ga 2− x Mn x Ge 3 O 12 garnets with x < 0.06 were examined versus temperature and pumping intensity. Unusual features of the kinetics of photoinduced phenomena are indicative of the underlying electronic processes. The comparison with the case of Ca 3 Mn 2 Ge 3 O 12 , explored earlier by the authors, permits one to finally establish the main common mechanisms of photoinduced absorption and dichroism caused by random electric fields of photoproduced charges (hole polarons). The rate of their diffusion and relaxation through recombination is strongly influenced by the same fields, whose large statistical straggling is responsible for a broad continuous set of relaxation components (observed in the relaxation time range from 1 to about 1000 min). For Ca 3 Ga 2−x Mn x Ge 3 O 12 , the time and temperature dependences of photoinduced absorption and dichroism bear a strong imprint of structure imperfection increasing with x.

Effect of Temperature and High Pressure on Luminescence Properties of Mn3+ Ions in Ca3Ga2Ge3O12 Single Crystals

“…The reduction is as small as 0.05%. The oxygen position ( x , y , z ) = (0.10004(13), 0.19602(13), 0.28262(12)) marginally differs from that given in ref , that is, (0.0999, 0.1997, 0.2838). The dominating valence of the Mn dopant is Mn 3+ ; however, a small amount of Mn 4+ ions is present in the crystals, as shown in forthcoming paragraphs.…”

“…The Mn content in the charge was 0.82 wt %. The charge was heated at 900 °C for 25 h. The crystal was grown by pulling from the melt at a rate of 2 mm/h and a rotation rate of 30–40 cycles per minute (for more details, see refs and ).…”