For very high temperatures, the magnetization is zero, as it is at infinite temperature. To see this, note that if spin A has only a small correlation ε with spin B, and B is only weakly correlated with C, but C is otherwise independent of A, the amount of correlation of A and C goes like ε. For two spins separated by distance L, the amount of correlation goes as ε, but if there is more than one path by which the correlations can travel, this amount is enhanced by the number of paths.