Classical spin
= Classical spin
{title2=$|\mathbf S|=S$}
A classical spin is a fixed-length <vector> representing the orientation of a local <magnetic moment>. A classical limit of a large quantum <spin> replaces its components by this vector and minimizes the resulting <energy>. Its length is conventionally $S$ at leading order, whereas the exact quantum squared-spin <eigenvalue> is $S(S+1)$ in units $\hbar=1$.