Single crystals of hexagonal ferrites up to 1/2 in. long were grown from the system NaFeO2‐Fe2O3‐BaO‐MeO, where Me = divalent Zn, Co, Ni, or Mg. NaFeO2was 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 Ba2Me2Fe12O22(Y)and Ba2Me2Fe28O46(X), 3/2 for Ba3Me2Fe24O41(Z), 2/1 for Ba4Me2Fe36O60(U), and 1/2 for BaMe2‐Fe16O27(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 fromZby systematically adding blocks ofY.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 tw