15.4 Para-, Ferro-, Antiferro-, and Ferrimagnetism
As noted above, the vast majority of ceramics are diamagnetic with negative
susceptibilities (?al0-6). The effect is thus small and of very little practical
significance, and will not be discussed further. Instead, in the following
sections, the emphasis will be on by far the more useful and technologically
important classes of magnetic ceramics, namely, the ferro- and ferrimagnetic
ones. Before one considers these, however, it is important to understand the
behavior of another class of materials, namely, paramagnetic materials, not
because of their practical importance (very little) but because they represent
an excellent model system for understanding the other, more complex
phenomena.