Linked from
The 24 pages that link to Magnetic domain, each with the reason it gives.
FerromagnetismBroader topic: Ferromagnets divide into domains to reduce magnetic energy.
MagnetizationBroader topic: Domain alignment and wall motion change a material’s net magnetization.
Magnetic anisotropyRelated: Anisotropy helps determine which directions domain magnetization adopts.
Magnetic storageRelated: Aligned regions provide the physical magnetic states used in recording.