Biogenic Ferrimagnetism: A New Biomagnetism

Abstract

In its simplest form, biomagnetism is usually defined as the study of the magnetic fields originating in living systems, while the term magnetobiology refers to the effects of magnetic fields on organisms. Most biomagnetic research currently in progress today and discussed in other chapters deals with magnetic fields generated either by ionic currents flowing within an organism, those induced para- or diamagnetically by the application of external fields, or those produced by the transient high-field alignment of the magnetic moments of magnetic contaminants. However, there is another proper branch of biomagnetism that warrants discussion here: magnetic moments and fields produced by biochemically precipitated ferrimagnetic minerals. Unlike paramagnetic or diamagnetic substances, a ferrimagnetic particle of the proper size and shape will spontaneously produce a permanent magnetic moment which under normal biological conditions cannot be demagnetized. On a microscopic scale, the magnitude of the local magnetic field adjacent to these particles may be quite large, and the particles will interact strongly with the weak geomagnetic field.