A new class of oxidic ferromagnetic materials with hexagonal crystal structures

Several new groups of ferromagnetic oxides have been found. They have rather complicated chemical compositions and can be obtained as reaction products of Fe2O3, BaO and MeO in various proportions, where Me denotes, in general, an element of the first transition group, or either Mg or Zn. The crystal structures of these new compounds can be described in the hexagonal system and are related to the magnetoplumbite structure. The crystal anisotropy of many of these hexagonal compounds is such that, depending on the chemical composition, the spontaneous magnetization in each crystal is oriented either parallel or perpendicular to the hexagonal axis. In the latter case the magnetization can fairly easily be rotated in the basal plane. Polycrystalline sintered samples of such compounds show an initial permeability of about 10; the permeability remains substantially constant up to about 1000thinsp;Mc/s, so that these new materials extend the frequency range where ferromagnetic oxides can be advantageously used as core materials to frequencies much higher than is now possible with ferrites having cubic crystal structures. An earlier paper on these materials has been given elsewhere.1