permegnets.

Paramagnetism is a form of magnetism which
occurs only in the presence of an externally
applied magnetic field. Paramagnetic materials
are attracted to magnetic fields, hence have a
relative magnetic permeability greater than one
(or, equivalently, a positive magnetic
susceptibility). The magnetic moment induced
by the applied field is linear in the field strength
and rather weak . It typically requires a sensitive
analytical balance to detect the effect. Unlike
ferromagnets, paramagnets do not retain any
magnetization in the absence of an externally
applied magnetic field, because thermal motion
causes the spins to become randomly oriented
without it. Thus the total magnetization will drop
to zero when the applied field is removed. Even
in the presence of the field there is only a small
induced magnetization because only a small
fraction of the spins will be oriented by the
field. This fraction is proportional to the field
strength and this explains the linear
dependency. The attraction experienced by
ferromagnets is non-linear and much stronger,
so that it is easily observed, for instance, in
magnets on one's refrigerator.