| part 1 - Why are things magnetic ? paramagnetic materials 1 | |||||||
 Fig. 1.6 |
Many materials have microscopic (atomic) magnetic moments μ,
nevertheless only very few materials are magnetic at the macroscopic
level, resulting in everyday magnets. Thermal agitation effectively
randomizes the orientation of these microscopic moments and the
macroscopic net-moment is zero (Fig. 1.6.a). However, magnetic moments
have a tendency to align themselves parallel to any external magnetic
field B (Fig. 1.6.b). This partial alignment of microscopic
moments results in a macroscopic magnetic moment parallel to the
external magnetic field Bext. This macroscopic
magnetic moment μnet increases with increasing Bext.
paramagnetic minerals have a weak but positive
magnetic susceptibility. Many iron-bearing minerals are paramagnetic. Since the alignment of microscopic magnetic moments is generally poor, paramagnetic effects tend to be rather small. Strongly magnetic materials are characterized by a very effective alignment process which will be discussed next.
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| part 1 - index | 1.1 currents | 1.2 solenoids | 1.3 electromagnets | 1.4 mag. moment | 1.5 diamagnets | 1.6 paramagnets | 1.7 mag. ordering |
