Biomedical Engineering Reference
In-Depth Information
Figure 9.40
Langevin's law for paramagnetic material. Magnetization is aligned with the magnetic
field.
�
changed in
-
�
), the magnetization is changed to its opposite (
M
is changed into
-
�
� �
), and the term
( .
M H
in the expression of the force remains identical.
9.13.3.2 Ferromagnetic Membranes
Ferromagnetic membranes show a different behavior when placed in an oscillating
magnetic field. When the external field vanishes, during a change from
H
�
to
-
�
,
there is still a remanent magnetization as shown in Figure 9.41.
An oscillating magnetic field is obtained by using a miniaturized electromagnet
and the delivered magnetic field is often weak, so that the magnetization of the fer-
romagnetic particles remains close to the remanent magnetization
�
M
. In this case,
the expression of the force is approximately
Figure 9.41
Magnetic moment of a ferromagnetic membrane, measured in the plane of the mem-
brane and along the axis perpendicular to the membrane.
