ABSTRACT
The spin magnetic moments within a ferromagnetic material interact with each other even when there is no external field present by a quantum mechanical exchange coupling force. These interactions cause the creation of a strong internal molecular magnetic field. This field causes neighboring moments to align themselves parallel to each other in regions called magnetic domains of size approx 10-7m. With no external field, the orientations of the domains are random. Within a domain, the orientation of the magnetic moments are aligned and the magnetization is at the saturation level. When an external field H is applied, the domains tend to reorient so that the effect of this is that those domains already in alignment with the field tend to grow in size at the expense of others, not aligned, which shrink. As H is increased, a saturation point is reached where all domains contain magnetic moments that are aligned with the field.
