The fundamental absorption edge in MnIn2Se4 layer semi-magnetic semiconductor

Effect of the paramagnetic to spin-glass phase transition on the fundamental absorption edge of MnIn2Se4 magnetic semiconducting compound

“…, where x is the thickness sample and R ≈ 0.223 [18], is the reflectivity. T r spectra were measured by using an Acton Research Spectra P-500 spectrometer in the energy range from 1.2 to 2.4 eV.…”

“…The nature of the fundamental absorption edge in MnIn 2 Se 4 was examined by us in a previous article [18] by studying the optical absorption coefficient spectra α c of this compound at several temperatures between 10 and 295 K. It was found, at values of α c lower than about 2 × 10 3 cm −1 , that the lowest energy gap is indirect. On the other hand, for values of α c greater than 2 × 10 3 cm −1 , the absorption coefficient spectra show the presence of two direct band-to-band transitions at higher energies.…”

“…On the other hand, for values of α c greater than 2 × 10 3 cm −1 , the absorption coefficient spectra show the presence of two direct band-to-band transitions at higher energies. These two processes, with characteristic energies E I GD and E II GD , correspond [18] to direct transitions from the uppermost Γ 4 (z) and the middle Γ 5 (z) valence bands, to the Γ 1 (s) conduction band of MnIn 2 Se 4 , respectively.…”

“…Here, the typical downward shift in the freezing temperature T f , when the frequency is decreased, was observed. The zero-frequency transition temperature is T f = (3.58 ± 0.02) K. On the other hand, analysis of its optical absorption coefficient spectra [1,18] reveals that the lowest-energy-gap of this compound is indirect between parabolic bands that vary from 1.55 to 1.43 eV in the temperature range from 10 K to 295 K [18]. This indirect band-to-band transition arises from the uppermost Γ 4 (z) valence band at Γ point, to the conduction band minimum located at a lower-symmetry point different from Γ [12].…”

“…This indirect band-to-band transition arises from the uppermost Γ 4 (z) valence band at Γ point, to the conduction band minimum located at a lower-symmetry point different from Γ [12]. Additionally [18], two direct band-to-band transitions, beginning at 1.72 and 1.85 eV, at 295K, and at 1.82 and 1.96 eV, at 10 K, from the uppermost Γ 4 (z) heavy-hole and middle Γ 5 (z) light-hole bands, to the Γ 1 (s) conduction band, were observed in the high energy region. At energies around 2.2 eV, an internal transitions from 6 A 1 ground state to the 4 T 1 d-excited level of Mn +2 ion, was also observed from photoluminescence spectra.…”