Two Paradigms of Magnetism

Magnetism is a macroscopic phenomenon with its origin deeply rooted in quantum mechanics.
In condensed matter physics, there are two paradigms for magnetism: localized spins
interacting via tunnelling, and delocalized spins interacting via an exchange energy. The latter
gives rise to itinerant ferromagnetism which is responsible for the properties of transition metals
like cobalt, iron and nickel. Both kinds of magnetism involve strong correlations and/or strong
interactions and are not yet completely understood. For localized spins, major open questions
include the interplay of magnetism with d-wave superfluidity and frustrated spin materials. For
itinerant ferromagnetism, phase transition theories are still qualitative.

What is needed for Itinerant Ferromagnetism?