Effect of magnetic transition on the lattice expansion of nickel

The lattice expansion in 99.999% pure nickel has been studied to within epsilon = mod (T-Tc)/Tc mod =10-3. It is observed that during the ferromagnetic-to-paramagnetic transition, nickel undergoes anomalous expansion leading to a lambda -type anomaly in the thermal expansion coefficient, beta (T). From beta (T), the critical part of the thermal expansion coefficient beta c(T) was separated and fitted to the power-law equation beta c+or-=(A+or-/ alpha +or-) epsilon - alpha +or-(1+E+or- epsilon x+or-)+B+or-. The parameters thus obtained are in good agreement with the values predicted by the renormalisation group theory and those derived from specific heat measurements.