Reduction in the rate of phonon scattering by a spatially correlated system of iron ions and low-temperature “anomaly” of the thermoelectric phenomena in HgSe:Fe crystals

A new effect of the reduction in the rate of phonon scattering by the spatially correlated system of iron ions in HgSe:Fe crystals is detected experimentally and calculated theoretically. The thermoelectric power is measured using HgSe:Fe samples with different iron content in the temperature range 7.5–60 K. It is found that the dependence of the thermoelectric power on iron content exhibits remarkable features at T<10 K: the quantity |α(N Fe )| increases as the iron concentration increases to N Fe =5×1018 cm−3, reaches a maximum at N Fe ≈(1–2)×1019 cm−3, but then monotonically decreases with further increases in N Fe . It is shown that the obseved increase in the thermoelectric power is due to a reduction in the rate of phonon scattering by the spatially correlated system of Fe3+ ions. This new effect is analyzed theoretically, and the theoretical results are compared with the experimental data.