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

The electrical resistivity {ρ} and the thermal diffusivity a of gadolinium have been measured as functions of T in the range 45--400 K. The thermal conductivity {λ} has been calculated from a and experimental data for the specific-heat capacity, cₚ. {λ} can be analyzed in terms of simple models for the lattice and electronic components above the Curie temperature TC{}291.4 K. Below TC an additional term, identified as a magnon (spin-wave) thermal conductivity λₘ, is found. {ρ} and {λ} 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={ρ}{λ}/T increases by about 20%/GPa under pressure due to a very strong pressure dependence of the lattice thermal conductivity. The pressure coefficients of {ρ} and {λ} are -5.1×{}10^-2 and 0.22 GPa^-1, respectively, at 300 K (above TC), and 0 and 0.16 GPa^-1 at 200 K (below TC). TC and the spin-reorganization temperature Tᵣ{}219 K both decrease under pressure, at the rates -14.0 and -22.0 K/GPa, respectively. Although the magnitude of λₘ cannot be accurately calculated from the zero-pressure data for {λ}, the temperature dependence of d{λ}/dP allows us to distinguish between several models and assign a value of λₘ{}1.5 W m^-1 K^-1, or 16.0% of {λ}, at 200 K.