Unusual specific heat of a linear-chain mercury compound

Abstract

The temperature dependence of the low-temperature specific heat and the magnetic susceptibility for the linear-chain mercury compound ${\mathrm{Hg}}_{2.86}$As${\mathrm{F}}_6$ are reported. The measured specific heat from 1.9 to 5 K exhibits an unusually large linear term contribution ${\gamma }^T$ where $\gamma =46\mathrm{}$ mJ/(${\mathrm{K}}^2$ g-atom Hg), while the density of states from the temperature-independent spin susceptibility is relatively small. The data are discussed in terms of several contributions to the linear term $\gamma$ which include phonon excitations of separate hard one-dimensional and soft three-dimensional lattices and excitations arising from disorder within the mercury chains.