Another important quantity is the correlation length, which is expected to be of the order of the lattice spacing for \( T \) is close to \( T_C \). Because the spins become more and more correlated as \( T \) approaches \( T_C \), the correlation length increases as we get closer to the critical temperature. The discontinuous behavior of the correlation \( \xi \) near \( T_C \) is $$ \begin{equation} \xi(T) \sim \left|T_C-T\right|^{-\nu}. \tag{1} \end{equation} $$