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How does magnetic saturation occur in a ferromagnetic material?

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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.

In a ferromagnetic material, magnetic saturation occurs when an external magnetic field is strong enough to align all of the material's internal magnetic domains parallel to the direction of that field.

The process of reaching this state involves three primary stages as the magnetizing force increases:

Low field: Domains oriented in the direction of the field grow at the expense of unfavorably oriented ones through reversible domain wall movements.
Medium field: Larger, often irreversible movements of domain walls occur, significantly increasing the volume of favorably oriented domains.
High field: Remaining domain walls are swept out of the specimen. The magnetization directions of the remaining domains gradually rotate until they are everywhere parallel to the applied field.

At this limiting state, known as saturation, the entire object effectively acts as a single domain. Further increases in the external field strength produce no significant increase in the material's magnetization, as the maximum possible alignment has been achieved.123