Dipole-dipole interactions and the critical resistivity of gadolinium

Results are presented for the electrical resistivity of a c-axis single crystal of high-purity gadolinium metal in the immediate vicinity of the Curie temperature. Numerical analysis reveals that the data are not well described by the usual power laws in (T-$T_c$)/$T_c$ but tend to exhibit a change in effective slope at $T_c$ which can be described by classical Landau theory with logarithmic corrections. This is interpreted in terms of the dipole-dipole interactions, which are shown to become important at about 1 K above $T_c$. We suggest that gadolinium is a uniaxial dipolar ferromagnet in the asymptotic critical-behavior regime.