= Ferromagnetism
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<Ferromagnetism> is collective magnetic order with <spontaneous magnetization> below a <Curie temperature>. Interactions favor aligned <magnetic moments>; the <Ising model> represents a two-orientation version with positive coupling.
A <magnetic domain> can possess <spontaneous magnetization> even when other domains cancel its contribution to the whole specimen. Compare this spatial cancellation between domains with <antiferromagnetism>, where opposing <magnetic sublattices> compensate within the ordered structure, and <ferrimagnetism>, where their contributions are generally unequal. The <magnetic sublattice> diagram makes the three local patterns explicit.
Smoothly sweeping an applied <magnetic field> can reveal abrupt <magnetization> changes through the <Barkhausen effect>. A <pickup coil> detects the resulting changes of <magnetic flux>, making collective <magnetic domain wall> motion accessible as an electrical <signal>.
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