A fused-quartz dilatometer was used to measure the thermal-expansion coefficient $\alpha$ of nickel between 300 and 1000 K. Measurements on National Bureau of Standards certified copper and tungsten standards with the dilatometer established the uncertainty in the $\alpha$ measurements on nickel as ± 0.8% (±0.10 × ${10}^{-6\mathrm{}}$ ${\mathrm{K}}^{-1\mathrm{}}$), except within ± 2 K of the Curie temperature $T_C$ where the uncertainty was about ± 1.6%. Results of 38 investigations of the expansion of nickel reported in the literature were analyzed critically, resulting in a compilation of $\alpha$ of nickel from 0 to 1500 K. Theories of thermal expansion were employed to separate $\alpha$ into its paramagnetic ${\alpha }_p$ and magnetic ${\alpha }_m$ components. The calculated values of ${\alpha }_m$ near $T_C$ were fitted to the power-law equation, ${\alpha }_m=A(t^{-a}-1)a^{-1\mathrm{}}+B$, that describes critical phenomena near the critical temperature [$t=(T-T_C)T_C^{-1\mathrm{}}$]. It was demonstrated that the critical exponents above and below $T_C$, $a$ and $a^{\prime }$, respectively, are the same as those derived from specific-heat measurements and that $a=a^{\prime }=-0.093(\pm 0.010)$ in agreement with scaling laws of critical phenomena.

• Received 11 April 1977

DOI:https://doi.org/10.1103/PhysRevB.16.4872