Structural and electronic transitions in thulium-substituted manganese selenide

https://doi.org/10.1016/j.ceramint.2022.06.244

The structural, transport, optical, and acoustic properties of a new TmXMn1‒XSe (0 ≤ Х ≤ 0.2) chalcogenide system have been studied in the temperature range of 80–500 K. The morphology and microstructure of the polycrystalline samples have been studied by scanning electron microscopy. Temperatures of maxima of the thermal expansion and sound attenuation coefficients related to the lattice strain and electronic transitions have been determined. The variation in the energy of activation of carriers near the percolation concentration caused by a change in the thulium valence has been revealed. The type of majority carriers has been established from the thermopower data. The temperature range of the anomalous compressibility associated with delocalization of electrons has been found from the temperature dependence of the thermal expansion coefficient. Jahn‒Teller polarons have been found above the percolation concentration using the infrared spectroscopy data.