Phenomenology of ferromagnetism. I. Effects of magnetostatics on susceptibility

Magnetic measurements, with particular emphasis on finite cylinders of iron in the form of whiskers, are interpreted with regard to magnetostatic effects. Demagnetizing fields are calculated using various degrees of approximation. In the cases considered the magnetostatic effects are dominant over other contributions to the micromagnetic energies. A particular approximation in which the demagnetizing field is assumed to be proportional to the second derivative of the magnetization is used to describe the sharp changes in response with field that occur near the Curie temperature