An electron microscopical study: Some effects of magnetic field upon single, anisotropic alpha iron crystals and the relation between their fine structure and magnetic properties
In this discussion of the magnetic properties of these same crystals we are dealing only with those forms which we have described previously as “rods”, “needles”, “nodular rods” or “dendrites with relatively short secondary arms”. Except for their small dimensions, these microscopic crystals are somewhat like “whiskers”, in that they appear to be single and are monolithic as far as our observation can detect. Monolithicity cannot be demonstrated in the more complex forms of the dendrites where overlapping of structures confuses observation, but in the less complex forms, namely rods and needles, it is seen that there is no beadlike appearance, as is observed in iron particles made by a process of electro-deposition into mercury (1). They would therefore be expected to act with the magnetic behaviour associated with shape anisotropy, and as elongated, single crystals, rather than as strings of separate crystals. As such they would be expected to yield exceptionally high coercive force when compacted and aligned.
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