  The mean field solution of the Ising model on a Barabasi-Albert scale-free
network with ferromagnetic coupling between linked spins is presented. The
critical temperature $T_c$ for the ferromagnetic to paramagnetic phase
transition (Curie temperature) is infinite and the effective critical
temperature for a finite size system increases as the logarithm of the system
size in agreement with recent numerical results of Aleksiejuk, Holyst and
Stauffer.
