Structural and optical high-pressure study of spinel-type MnIn2S4
Résumé
We report a combined study of the structural and electronic properties of the spinel-type semiconductor MnIn2S4 under high pressures by means of X-ray diffraction (ADXRD), X-ray absorption (XAS), and op- tical absorption measurements. The three techniques evidence a reversible structural phase transition near 7 GPa, that according to ADXRD measurements is to a double-NaCl structure. XAS measurements evi- dence predominant tetrahedral coordination for Mn in the spinel phase that does not noticeably change with increasing pressure up to the phase transition. XAS measurements indicate that the static disorder in- creases considerably when the sample reverts from the double-NaCl phase to the spinel phase. Optical ab- sorption measurements show that the direct gap of MnIn2S4 exhibits a nonlinear behaviour with a positive pressure coefficient at pressures below 2.5 GPa and a negative pressure coefficient between 2.5 and 7 GPa. The pressure behavior of the bandgap seems to be affected by the defect concentration. The dou- ble-NaCl phase also exhibits a bandgap with a negative pressure coefficient.