Question

(a) On the atomic level, what distinguishes ferromagnetic, ferrimagnetic, and antiferromagnetic materials from each other? (b) Which one of these types of magnetic materials cannot be used to make a permanent magnet?

Short answer

(a) Ferromagnetic materials have parallel-aligned magnetic moments, leading to a net magnetic field. Ferrimagnetic materials have parallel-aligned magnetic moments of different magnitudes, causing a partial cancellation and a smaller net magnetic moment. Antiferromagnetic materials have antiparallel magnetic moments, resulting in a net magnetic moment of zero. (b) Antiferromagnetic materials are unsuitable for making permanent magnets.

Step-by-step solution

Ferromagnetic materials

Ferromagnetic materials have atomic magnetic moments that align parallel to each other, giving rise to a net magnetic field even when there is no external field applied. They are characterized by strong magnetic domains, which form spontaneously due to strong atomic-level interactions. Some examples of ferromagnetic materials include iron, cobalt, and nickel.

Ferrimagnetic materials

Ferrimagnetic materials have two different types of magnetic moments that align parallel to each other but with different magnitudes. These unequal magnitudes partially cancel out each other's effect, and as a result, ferrimagnetic materials have a net magnetic moment, but it is less than that of ferromagnetic materials. A common example of a ferrimagnetic material is magnetite (Fe3O4).

Antiferromagnetic materials

Antiferromagnetic materials consist of atomic magnetic moments that align antiparallel to each other, resulting in a net magnetic moment of zero. This means that there is no net magnetic moment in the material when there is no external magnetic field applied. These materials typically exhibit magnetic ordering only below a certain temperature called the Néel temperature. Examples of antiferromagnetic materials include manganese oxide (MnO) and chromium.

Identifying the material unsuitable for permanent magnets

To make a permanent magnet, a material needs to possess a net magnetic moment even in the absence of an external magnetic field. Since antiferromagnetic materials have a net magnetic moment of zero, they cannot be used to make permanent magnets.

Answer

(a) On the atomic level, ferromagnetic materials have magnetic moments that align parallel to each other, giving rise to a net magnetic field. Ferrimagnetic materials also have aligned magnetic moments, but different magnitudes partially cancel each other out, resulting in a smaller net magnetic moment. Antiferromagnetic materials have antiparallel magnetic moments, resulting in a net magnetic moment of zero. (b) Antiferromagnetic materials cannot be used to make a permanent magnet.