Even non-magnetic materials exhibit magnetic
behaviour under the influence of a magnetic field. This
property, known as
diamagnetism
is actually a kind of anti-magnetism because the induced field opposes
the surrounding field and repels both poles. Diamagnetism is usually very
weak but in a field of sufficient strength (10 Tesla or
more) it is sufficient to cause small objects to levitate.
The effect can be further amplified to enable the levitation of rocks by
bathing the subject in liquid oxygen (although this is not really recommended for home experimenters).