Which materials are named as exhibiting strong magnetic effects and being called ferromagnetic?

1. Only certain materials exhibit strong magnetic effects, and these are called ferromagnetic. 2. The materials named are iron, cobalt, nickel, and gadolinium. 3. Metals such as copper, aluminium, gold and silver are not part of this named group of strongly magnetic materials. _Source: OpenStax Physics (CC BY 4.0), Ch 20 "Magnetism", section 20.1 Magnetic Fields, Field Lines, and Force_