| Material |
cm=Km-1
(x 10-5)
| |
| Paramagnetic |
| Iron aluminum alum |
66 |
| Uranium |
40 |
| Platinum |
26 |
| Aluminum |
2.2 |
| Sodium |
0.72 |
| Oxygen gas |
0.19 |
| Diamagnetic |
| Bismuth |
-16.6 |
| Mercury |
-2.9 |
| Silver |
-2.6 |
| Carbon (diamond) |
-2.1 |
| Lead |
-1.8 |
| Sodium chloride |
-1.4 |
| Copper |
-1.0 |
| Paramagnetism |
Diamagnetism |
|
Here the quantity Km is
called the relative permeability, a quantity which measures the
ratio of the internal magnetization to the applied magnetic field.
If the material does not respond to the magnetic field by
magnetizing, then the field in the material will be just the
applied field and the relative permeability Km =1. A
positive relative permeability greater than 1 implies that the
material magnetizes in response to the applied magnetic field. The
quantity cm is called magnetic susceptibility, and it
is just the permeability minus 1. The magnetic susceptibility is
then zero if the material does not respond with any magnetization.
So both quantities give the same information, and both are
dimensionless quantities.
For ordinary solids and liquids at
room temperature, the relative permeability Km is
typically in the range 1.00001 to 1.003. We recognize this weak
magnetic character of common materials by the saying "they
are not magnetic", which recognizes their great contrast to
the magnetic response of ferromagnetic materials. More precisely,
they are either paramagnetic or diamagnetic, but that represents a
very small magnetic response compared to ferromagnets.
|