New Mn-Substituted Hexagonal Ferrites

Abstract

Seven new hexagonal ferrite structures have been identified by single-crystal x-ray diffraction during a study of crystals from Mn-substituted Y phase syntheses. They fall in the M2Yn series and are comprised of a c-axis stacking of 2 five-anion-layer M blocks permuted with 9–13 six-anion-layer Y blocks. The series is thereby extended to larger unit cells and the total number of known hexagonal ferrites raised to 31. Three of the new structures are hexagonal, four are rhombohedral; in polytypic nomenclature they are 192Rc, 70Hb, 228Ra, 76Ha, 76Hb, 228Rd, and 264Re. The latter has a c-axis repeat period of 264 anion layers; a=5.88 Å (common to all hexagonal ferrites), c=636.7 Å. Weissenberg x-ray patterns and 00·l diffractometer traces established symmetry and identity layering. Stacking models were confirmed by 00·l structure-factor computations.