In general, ferromagnets are divided into
magnetic domains and separated by surfaces known as Bloch walls.
The bias magnet provides a magnetic field to orient the
magnetic domains along the y-axis direction.
The nonmagnetic layer can then influence the magnetic one, with electric fields in the nonmagnetic layer pushing around the
magnetic domains in the magnetic layer.
Each of these
magnetic domains is made of a large collection of magnetised atoms, whose magnetic polarity is set by the hard disk's read/write head to represent data as either a binary one or zero.
The net result can be a reduction in the magnon-drag thermopower at high magnetic fields and when all
magnetic domains are aligned in the direction of the applied magnetic field.
Other topics include magnetization and magnetic moment,
magnetic domains, magnetic order and critical phenomena, quantum theory of magnetism, and the magnetic evaluation of materials.