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-Tc)/Tc but tend to exhibit a change in effective slope at Tc 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 Tc. We suggest that gadolinium is a uniaxial dipolar ferromagnet in the asymptotic critical-behavior regime.