As a necessary condition, ferromagnetism in elements require the existence of unpaired electrons. However, all elements with unpaired electrons are not ferromagnetic, e.g., metals such as aluminium or copper are either paramagnetic or diamagnetic. Why doesn't all elements with unpaired electrons become ferromagnetic? In addition to unpaired electrons, what extra conditions need to be satisfied for elements to exhibit ferromagnetism (or exchange interaction)?

As a necessary condition, ferromagnetism in elements requires the existence of unpaired electrons. However, all elements with unpaired electrons are not ferromagnetic, e.g., metals such as aluminium or copper are either paramagnetic or diamagnetic. Why don't all elements with unpaired electrons become ferromagnetic? In addition to unpaired electrons, what extra conditions need to be satisfied for elements to exhibit ferromagnetism (or exchange interaction)?