For 10 points, name this type of permanent magnetism held by such metals as nickel, copper, and iron.
The loss of energy due to lag in the acquisition of this phenomenon is given by the Steinmetz equation. One model for this behavior sees it as a linking of discrete spin states in a lattice by a positive interaction coefficient given by the half difference in energy between the spin states. With phase changes described by that Ising model, this phenomenon's acquisition as a function of an external field can be plotted on a hysteresis curve. As it is acquired, Barkhausen noise results from the discrete changes in this phenomenon when a magnetic field is applied to a material. It disappears altogether above the Curie point. For 10 points, name this type of permanent magnetism held by such metals as nickel, copper, and iron.
The loss of energy due to lag in the acquisition of this phenomenon is given by the Steinmetz equation.
{ferromagnetism} [prompt on {magnetism}]