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

Ir4+, substituted in ferroxdure (BaFe12O19), has been observed to couple ferrimagnetically. Replacement of Fe3+ by Ir4+Zn2+, according to the formula BaFe12−2x3+Irx4+Znx 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.