Final answer:
Ferromagnetic materials like iron, cobalt, nickel, and rare earth alloys show strong magnetic properties. These materials form permanent magnets with magnetic domains that contain aligned dipoles. Neodymium is an example of a rare earth element used to create strong, permanent magnets. Thus, the option "C" is the correct answer.
Step-by-step explanation:
A magnet is an object that exhibits a strong magnetic force and can either attract or repel other magnetic materials. Ferromagnetic materials such as iron, cobalt, nickel, and gadolinium, as well as alloys of the rare earth elements, have the capability to form permanent magnets. These materials contain regions called magnetic domains where the dipoles are aligned due to quantum mechanical effects, resulting in a substantial net dipole moment.
The ferromagnetism in these materials is so strong that it can persist for a long time, making these materials ideal for creating permanent magnets. One notable rare earth element used in powerful magnets is neodymium. The process of magnetization involves aligning the atomic magnets within a material, usually into domains, through the application of an external magnetic field.
All materials exhibit some form of magnetism, but it's the ferromagnetic materials that are commonly used in magnets due to their strong magnetic effects and the ability to retain magnetization. Unlike paramagnetic materials, which only exhibit magnetism when an external magnetic field is applied, ferromagnetic materials can become permanent magnets, maintaining magnetism even after the external field is removed.