Critical behaviour in the transport properties of pure iron

Abstract

Thermal conductivity, electrical resistivity, Lorenz number and spontaneous magnetisation have been measured for spectroscopically pure, polycrystalline iron from about room temperature to above 1200K. Emphasis has been placed on the region around the Curie temperature. The rate of change in electrical resistivity with temperature diverges approximately logarithmically on either side of the Curie point, in reasonable agreement with recent theory which links its behaviour with that of the magnetic specific heat. A predicted link with the spontaneous magnetisation is not supported by the data at least in the range 8.5*10-3<or approximately= mod epsilon mod <or approximately=10-1. Anomalous behaviour is observed in the total thermal conductivity and is attributed partly to the critical scattering of phonons by the spin system, the lattice component of thermal conductivity being estimated at about 25% of the total. The data are also consistent with a divergence in the temperature derivative of the electronic component of the thermal resistivity, as found recently in other metallic systems.