Abstract
This paper proposes a mechanism of formation of the magnetic domains on cooling a ferromagnetic material from a higher temperature than the Curie temperature. It is derived from the well-known theory of crystallization in an amorphous material through a two-step mechanism of nucleation and crystal growth. Following this approach it is shown that the domain structure should depend on the free-energy change ΔG per mole of magnetic moment aligning in the same direction. A method to avoid calculation of ΔG is shown. This approach was successfully applied to explain the differences between the domain structures of the annealed and the as-quenched samples of the amorphous alloy Fe62.5Co6Ni7.5Zr6Cu1Nb2B15. Moreover, it gives an explanation for recent findings on the magnetic microstructure of high-permeability materials.