= Spin glass
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A <spin glass> has frozen, irregular local <spin magnetization> without the periodic magnetic order of a simple <ferromagnet> or <antiferromagnet>. Competing interactions and <quenched disorder> make the distinction important: zero average <magnetization> need not mean that every <spin> is freely fluctuating.<Solvable Model of a Spin-Glass by David Sherrington and Scott Kirkpatrick>[pp. 1792–1794, introduction and interpretation of the frozen-moment order parameter]{ref}
The <frustrated Ising triangle> gives a small example of incompatible local preferences. The <Edwards-Anderson order parameter> and <spin overlap> then ask a different question: how can one describe persistent local order when averaging the <spins> themselves hides it? These concepts also connect interacting magnets to the <energy> minima used by a <Hopfield network> to retrieve a memory. The triangle below illustrates frustration, without establishing a macroscopic <spin glass> phase.
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