Thermal conductivity and electrical resistivity of gadolinium as functions of pressure and temperature

The electrical resistivity \ensuremath{\rho} and the thermal diffusivity a of gadolinium have been measured as functions of T in the range 45--400 K. The thermal conductivity \ensuremath{\lambda} has been calculated from a and experimental data for the specific-heat capacity, ${c}_{p}$. \ensuremath{\lambda} can be analyzed in terms of simple models for the lattice and electronic components above the Curie temperature ${T}_{C}$\ensuremath{\simeq}291.4 K. Below ${T}_{C}$ an additional term, identified as a magnon (spin-wave) thermal conductivity ${\ensuremath{\lambda}}_{m}$, is found. \ensuremath{\rho} and \ensuremath{\lambda} have also been studied as functions of T and P in the range 150--400 K and 0--2.5 GPa. The Lorenz function L=\ensuremath{\rho}\ensuremath{\lambda}/T increases by about 20%/GPa under pressure due to a very strong pressure dependence of the lattice thermal conductivity. The pressure coefficients of \ensuremath{\rho} and \ensuremath{\lambda} are -5.1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}2}$ and 0.22 ${\mathrm{GPa}}^{\mathrm{\ensuremath{-}}1}$, respectively, at 300 K (above ${T}_{C}$), and 0 and 0.16 ${\mathrm{GPa}}^{\mathrm{\ensuremath{-}}1}$ at 200 K (below ${T}_{C}$). ${T}_{C}$ and the spin-reorganization temperature ${T}_{r}$\ensuremath{\simeq}219 K both decrease under pressure, at the rates -14.0 and -22.0 K/GPa, respectively. Although the magnitude of ${\ensuremath{\lambda}}_{m}$ cannot be accurately calculated from the zero-pressure data for \ensuremath{\lambda}, the temperature dependence of d\ensuremath{\lambda}/dP allows us to distinguish between several models and assign a value of ${\ensuremath{\lambda}}_{m}$\ensuremath{\simeq}1.5 W ${\mathrm{m}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{K}}^{\mathrm{\ensuremath{-}}1}$, or 16.0% of \ensuremath{\lambda}, at 200 K.