Thermally activated motion of jogged screw dislocations has been used as the rate controlling mechanism in creep. Apparent activation energies for creep in a Fe – 7.5 at. % Si alloy have been experimentally determined by the temperature cycling technique over both the ferromagnetic and the paramagnetic temperature ranges. The result shows that there is a sudden change in the free energy of activation for self-diffusion at the Curie temperature and this is in agreement with a similar change in Young's modulus.