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 M₂Y_n 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 192R_c, 70H_b, 228R_a, 76H_a, 76H_b, 228R_d, and 264R_e. 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.