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Absorption Edge of MnGa 2 Se 4 Single Crystals under Hydrostatic Pressure
Author(s) -
González J.,
Rico R.,
Calderón E.,
Quintero M.,
Morocoima M.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199901)211:1<45::aid-pssb45>3.0.co;2-8
Subject(s) - absorption edge , tetragonal crystal system , hydrostatic pressure , band gap , analytical chemistry (journal) , materials science , absorption spectroscopy , absorption (acoustics) , direct and indirect band gaps , hydrostatic equilibrium , phase transition , semiconductor , chemistry , crystallography , optics , condensed matter physics , crystal structure , optoelectronics , thermodynamics , physics , chromatography , composite material , quantum mechanics
The semimagnetic semiconductor MnGa 2 Se 4 is a direct energy gap material ( E g = 2.7 eV at 300 K) crystallizing in the tetragonal structure, space group I4‐. In this paper, the optical absorption edge of MnGa 2 Se 4 was measured as a function of pressure up to 13 GPa. The measurements were performed in a diamond‐anvil cell at ambient temperature using a 4:1 mixture of methanol and ethanol as pressure‐transmitting medium. The direct energy gap (Γ v1 3 → Γ c1 1 ) increases linearly with pressure at the rate of 2.5 × 10 —2 eV GPa —1 . At 4.1 GPa the character of the fundamental gap changes to pseudodirect (Γ v1 3 → Γ c2 3 ). This direct gap decreases with pressure at the rate of —4.6 × 10 —2 eV GPa —1 . The absorption band at energies below the direct gap is attributed to manganese 6 A 1 → 4 T 2 intraionic transitions and shows a red shift under pressure. A first‐order structural phase transition was observed at 12.8 GPa in the upstroke. (The samples turn black when observed visually under a microscope.)