Estimates of the thermal-to-percolation crossover exponent in the transition to ferromagnetism induced by Ni impurities in Cu and Pd

An analysis of previously acquired data on the concentration dependence of the paramagnetic to ferromagnetic critical temperature, Tc(p), for the CuNi and PdNi systems (i) indicates that the Tc(p) are consistent with the predictions of percolation theory, viz. Tc(p)∝(p−pc)φ, (ii) provides a first estimate of the thermal-to-percolation crossover exponent φ for these systems, showing it to be consistent with Heisenberg model predictions, and (iii) confirm earlier estimates for the percolation thresholds, pc, obtained from other data.