If an initially non-magnetised ferromagnetic material is placed inside a magnetic field, generated by (say) a solenoid, it may be magnetised by increasing the current flowing in the solenoid. As the ferromagnetic material becomes increasingly magnetised, more and more of its domains line up and point in the same direction as the applied magnetic field. This process of increasing the strength of the applied field may continue until all of the ferromagnetic material's domains point in the same direction as the direction of the applied magnetising field. At this point, in the magnetisation history of the material, it is said to be magnetically saturated and it cannot be magnetised any further. A graphical plot of the materials magnetic field strength H versus the magnetic flux B provides the initial magnetisation curve. If the current flowing in the solenoid is turned back to zero then the applied field may be removed. The ferromagnetic material will now have a remanence of aligned domains and will, thus , still be magnetised. When the current in the solenoid flows in the opposite direction, the ferromagnetic material may be magnetised to domain alignment saturation in the opposite magnetic orientation. Again, when the opposite applied field is removed the ferromagnetic material has a remanence of domain magnetism in the opposite direction to the previous remanence. Hence, a graphical plot of B (flux) versus H (field strength) for the major hysteresis curve shows the initial magnetisation to saturation and then the reverse saturation with non-applied field remanence’s in between.

The area under the hysteresis curve represents energy lost in the cycle of swinging the magnetic orientation of the ferromagnetic material. This lost energy takes the form of heat and this disrupts how the domains align during the next cycle. Furthermore, the domains slide past each other during the hysteresis cycle and this friction liberates more heat. Thus, thermal agitation from these two processes disrupts future hysteresis cycles and prevents them from having identical major B versus H plots as the previous ones. To summarise - the curve shape of the hysteresis cycle depends upon the magnetic history of the ferromagnetic material.