On the band gap and thermal expansion of MnIn5.0S8.5 single crystals

Abstract

MnIn5.0S8.5 single crystals are grown by the Bridgman method. The width and length of the crystals are ∼14 and ∼40 mm, respectively. The composition, structure and unit-cell parameter of the crystals are established. From the transmittance spectra recorded in the temperature range 20–300 K, the band gap Eg and its temperature dependence Eg(T) are determined. The dependence Eg(T) is adequately described by the corresponding theoretical expression. The specific expansion (Δl/l0) versus temperature is measured, and the coefficient of linear thermal expansion (αL) is determined. From the data on αL, the Debye temperature (ΘD) and the rms dynamic atomic displacements \((\sqrt {\bar u^2 } )\) are calculated. It is established that the Debye temperature ΘD decreases with increasing temperature, whereas the rms atomic displacements increase.