Growth and Properties of Single Crystals of Hexagonal Ferrites

Abstract

Single crystals of hexagonal ferrites up to 1/2 in. long were grown from the system NaFeO 2 ‐Fe 2 O 3 ‐BaO‐MeO, where Me = divalent Zn, Co, Ni, or Mg. NaFeO 2 was the flux from which crystals were grown in platinum crucibles from a maximum temperature of 1250° to 1375°C. More than 150 single‐crystal growth experiments were attempted and the reaction products were studied by X‐ray diffraction and optical microscopy. Stability data for the principal single‐crystal products are given for initial compositions lying in quaternary planes. Such planes were considered for BaO/MeO ratios corresponding to the compounds 1/1 for Ba 2 Me 2 Fe 12 O 22 (Y) and Ba 2 Me 2 Fe 28 O 46 (X) , 3/2 for Ba 3 Me 2 Fe 24 O 41 (Z) , 2/1 for Ba 4 Me 2 Fe 36 O 60 (U) , and 1/2 for BaMe 2 ‐Fe 16 O 27 (W) (Me = Zn, Co, Ni, or Mg). A number of adjoining planes were also considered. All the five known structure types were grown as single crystals. A series of four new hexagonal ferrite structures was discovered. These were derived from Z by systematically adding blocks of Y. Magnetization as a function of temperature and field was investigated for crystals of two structure types. The room‐temperature ferromagnetic resonance and effective anisotropy were studied for substituted crystals of the same two structure types.