Mössbauer-Effect Studies in Hafnium-Metal Single Crystals

Abstract

The M\"ossbauer effect in ${\mathrm{Hf}}^{178}$ has been studied with oriented single-crystal absorbers of hafnium metal at the temperature of liquid helium. Along the [0001] axis, only the $|\ensuremath{\Delta}m|=1$ component of the quadrupole spectrum is observed, and along the [1010] axis only the $|\ensuremath{\Delta}m|=1$ and $|\ensuremath{\Delta}m|=2$ components are observed. Combining these observations with those made using a polycrystalline hafnium-metal absorber, the magnitude of the electric field gradient was found to be ${V}_{\mathrm{zz}}=(0.95\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}{10}^{18}$ V/${\mathrm{cm}}^{2}$, and the asymmetry parameter $\ensuremath{\eta}<0.1$. The Debye temperature of hafnium carbide has been estimated to be (350\ifmmode\pm\else\textpm\fi{}10)\ifmmode^\circ\else\textdegree\fi{}K, and the Debye temperature of hafnium metal has been found to be (227\ifmmode\pm\else\textpm\fi{}10) and (192\ifmmode\pm\else\textpm\fi{}13)\ifmmode^\circ\else\textdegree\fi{}K, for $\ensuremath{\gamma}$ rays propagating parallel and perpendicular to the $c$ axis, respectively.