From another thread I think I understand that ferromagnetic material can exist any time, but dia & para magnetic materials exist only when there is an external field. My overview is Macroscopically ferro materials have to align their domains & can remain aligned when field is removed, leaving permanent dipoles. Para materials have relatively few permanent dipoles & are less likely to remain permanent. Diamagnetism only exists to oppose any external field in accordance with Lenz's law. Could someone confirm or clarify this set of statements, please.