Magnetic Properties of Fine Particles

There have not been many changes in the use or the understanding of the concept of superparamagnetism since Jacobs and Bean [1] reviewed it almost 30 years ago. The measuring techniques have improved during that time, and have become more accurate and more sophisticated, but their analysis and interpretation still use the same theory and the same crude approximations as in that review. It is not that new theoretical approaches have not been published, or that the published ones were too difficult or too complicated to use. These theories were just ignored.