Major phase transformations and magnetic property changes caused by electromagnetic fields at microwave frequencies

摘要

We demonstrate in this paper that common crystalline phases can be made noncrystalline and hard magnets can be converted to soft magnets in the solid state in several seconds at temperatures far below the melting points. New crystal structures and magnetic structures of ferromagnetic oxides (ferrites such as BaFe_(12)O_(19), CoFe_2O_4, Fe_3O_4, and ZnFe_2O_4, etc.) are formed by reacting either the stoichiometric mixture of oxides or the preformed phase-pure crystalline material in a pure H field (or E field) at microwave (2.45 GHz) frequencies. These major changes in the magnetic properties as well as major structural phase changes are caused by the magnetic field.