Influence of magnetism

Ferromagnetic materials are the only materials strong enough to be drawn to a magnet. That is why we call them magnetic.

However, all other substances also respond weakly to a magnetic field, via one or more other types of magnetism. When we expose a material to a magnetic field, it can respond in various ways. We distinguish between the following kinds of magnetism:

• Diamagnetism
• Ferromagnetism
• Antiferromagnetism
• Ferrimagnetism
• Paramagnetism

1. Pauli paramagnetism
2. Super paramagnetism

• Spin glass magnetism

When we speak of magnetic material, we mean that the material shows ferro- or ferrimagnetic behaviour.

The forces that occur with dia- and paramagnetic behaviour are much weaker. Moreover, these materials do not spontaneously produce their own magnetic field. We therefore consider them to be non-magnetic.

Diamagnetic materials tend to repel field lines from their core, while ferromagnetic, ferrimagnetic and paramagnetic materials tend to concentrate them.

A practical example of diamagnetism: water is weakly diamagnetic, about forty times less than, for example, pyrolytic carbon. This is enough for light objects - containing a lot of water - to float if they are in a strong magnetic field.

This frog started floating for example, using a 16 tesla electromagnet at the High Magnetic Field Laboratory at Radboud University Nijmegen in the Netherlands.