Specific Heat of Nickel near the Curie Temperature

Abstract

Using an ac calorimetric method, the specific heat $C_p\mathrm{}\left(T\right)\mathrm{}$ of pure single-crystalline Ni has been measured over a temperature range of 100 K centered at the Curie point (∼ 631 K). The experimental method permits continuous observation of $C_p$ vs $T$ with a temperature resolution of ∼ 0.01 K using very small specimens (∼ 7.8 mg). Special attention has been devoted to the determination of the analytical form of the magnetic contribution to $C_p\mathrm{}\left(T\right)\mathrm{}$. The effect of applied fields up to 240 Oe has also been studied. At zero field, the data fit a standard power-law expression over the range $-3.\mathrm{}2\le {log}_{10}\left|\frac{(T-T_c)}{T_c}\right|\le -1.\mathrm{}6$, with exponents $\alpha ={\alpha }^{\prime }=-0.\mathrm{}10\pm 0.03$. The data obtained with applied field follow the scaling relations calculated by Griffiths from the magnetic equation of state. The observed rounding of the specific-heat curve at its maximum is discussed and some experimental factors which influence the degree of the observed rounding are described.