The physical development of a magnetic crystal is governed by two factors: one is moving to align the magnetic force of the molecules in conjunction with the developing crystal, while the other reduces the magnetic force of the crystal, allowing an attachment of the molecule while experiencing an opposite magnetic force. In nature, this causes the existence of a magnetic domain, surrounding the perimeter of the domain, with a thickness of approximately 150 nm of magnetite, within which the molecules gradually change orientation. For this reason, the iron is not magnetic in the absence of an applied field.