Pressure effects on the crystal field and luminescence Stokes shift of Mn²⁺ (T_d) in [(CH₃)₄N]₂MnX₄ (X: Cl, Br) by time-resolved spectroscopy

Abstract

This work investigates the Mn²⁺ electronic structure and photoluminescence (PL) in [(CH₃)₄N]₂MnCl₄ and [(CH₃)₄N]₂MnBr₄ and their variation with pressure by time-resolved excitation and emission spectra in the 0–10 GPa range. We show that both the crystal-field excitation and corresponding PL bands experience large-pressure redshifts (about 5 nm/GPa), which are associated with the high crystal compressibility and the interaction between organic/inorganic ([CH₃]₄N⁻/MnX) tetrahedra. The energy variation as a function of pressure is explained in terms of the isolated T_d MnX in the respective crystals through crystal-field models. One salient feature is the reduction of the PL Stokes shift with pressure in both crystals as−1.0 and−1.7 nm/GPa for chloride and bromide, respectively.

^†This paper was presented at the XLVI^th European High Pressure Research Group (EHPRG 46) Meeting, Valencia (Spain), 7–12 September, 2008.

Keywords:

• Mn²⁺ T_d/O_h
• crystal field
• Stokes shift
• time-resolved spectroscopy

Acknowledgements

Financial support from the Spanish MEC (Project No. MAT2005-00099) and MALTA INGENIO-CONSOLIDER 2010 (Ref. CDS2007-0045) are acknowledged. Y. Rodríguez-Lazcano and L. Nataf thank financial support from the Mobility Program (Ref. SB2005-0201) and Postdoctoral fellowship from the University of Cantabria, respectively.

Notes

^†This paper was presented at the XLVI^th European High Pressure Research Group (EHPRG 46) Meeting, Valencia (Spain), 7–12 September, 2008.