Single-Crystal Ferroxdure, BaFe12−2x3+Irx4+Znx 2+O19, with Strong Planar Anisotropy

Abstract

Ir⁴⁺, substituted in ferroxdure (BaFe₁₂O₁₉), has been observed to couple ferrimagnetically. Replacement of Fe³⁺ by Ir⁴⁺Zn²⁺, according to the formula BaFe_12−2x³⁺Ir_x⁴⁺Zn_x ²⁺O₁₉, reduces the intrinsic axial anisotropy. The room temperature anisotropy becomes planar at x=0.3–0.4 and increases to 22 000 Oe at x=0.6. Magnetization and Curie temperature are decreased by the substitution of Ir⁴⁺Zn²⁺; ferrimagnetic resonance linewidth is increased. The nonaxial anisotropy is believed to derive from spin‐orbital coupling of Ir⁴⁺. Single crystals up to ¼ in. across were grown from a Bi₂O₃ flux in platinum crucibles. Specimens are hexagonal tabular, black, lustrous, and well‐developed. Single‐crystal x‐ray diffraction patterns showed that a₀ increases with increasing Ir⁴⁺Zn²⁺ substitution while c₀ remains unchanged.