Specific Heat of Nickel near the Curie Temperature

Abstract

Using an ac calorimetric method, the specific heat ${C}_{p}(T)$ of pure single-crystalline Ni has been measured over a temperature range of 100 K centered at the Curie point (\ensuremath{\sim} 631 K). The experimental method permits continuous observation of ${C}_{p}$ vs $T$ with a temperature resolution of \ensuremath{\sim} 0.01 K using very small specimens (\ensuremath{\sim} 7.8 mg). Special attention has been devoted to the determination of the analytical form of the magnetic contribution to ${C}_{p}(T)$. 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 $\ensuremath{-}3.2\ensuremath{\le}{log}_{10}|\frac{(T\ensuremath{-}{T}_{c})}{{T}_{c}}|\ensuremath{\le}\ensuremath{-}1.6$, with exponents $\ensuremath{\alpha}={\ensuremath{\alpha}}^{\ensuremath{'}}=\ensuremath{-}0.10\ifmmode\pm\else\textpm\fi{}0.03$. 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.