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Why can an unmagnetized piece of iron contain many tiny magnetic domains?

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Diagram showing a circular loop of wire with an electric current, surrounded by curved blue lines representing magnetic field lines that loop around the wire and pass through its center. — magnetism Some lines of the magnetic field B (blue) for an electric current I (gold) in a loop.

An unmagnetized piece of iron contains many tiny magnetic domains because this configuration minimizes the material's total internal energy.1

While the interatomic forces in ferromagnetic materials cause the magnetic moments of neighboring atoms to align spontaneously, a sample where all atomic moments pointed in the same direction would possess exceptionally high energy. To reduce this energy, the material naturally breaks up into numerous small regions called [domains]. Within each domain, all atomic magnetic moments are aligned to saturation, but the directions of magnetization in adjacent domains are oriented randomly or in opposing directions.123

Because these individual domain magnetizations are distributed at random, their magnetic effects cancel one another out, causing the iron as a whole to appear unmagnetized. The existence of these domains is a fundamental aspect of ferromagnetism, and the material only displays a net magnetic field when an external force causes these domains to align or grow in a specific direction.231