Diamagnetic

The three ferromagnetic metals, iron, cobalt and nickel are strongly affected by magnetic fields. Other materials are described as being non magnetic but strictly speaking they are not. They do respond to magnetic forces, but the effect is many thousands of time weaker. Materials are classed as paramagnetic or diamagnetic depending on whether they are attracted or repelled in a magnetic field.

Diamagnetic materials

Some materials (including some metals, water and living animals) are diamagnetic. They are very weakly repelled in a magnetic field. It is possible to suspend tiny chips of graphite (pencil lead) and small frogs in very strong magnetic fields.

The strength of the effect is quoted as the magnetic susceptibility Cm which is close to - 0.00002 for mercury, silver, graphite and lead, and -0.000009 for water. The corresponding value for bismuth is - 0.00016. Bismuth is repelled more strongly than water and the other metals.

Many other materials are paramagnetic