Synthesis, X-Ray, Neutron and Magnetic Studies of New In-Plane Anisotropy M-Hexaferrites BaFe_12-2xA_xMe_xO₁₉ (A = Ru, Ir ; Me = Co, Zn)

Abstract
Ti-Co substituted M-hexaferrites have been extensively investigated as promising materials for magnetic recording or microwave devices. Doping BaM hexaferrite with Ru-Me or Ir-Me (Me = Zn, Co), compounds are obtained with much higher Tc and Ms values than with Ti-Co elements. Powders and single crystals of BaFe_12-2xA_xMe_xO₁₉ have been prepared. Magnetization measurements have been performed on single crystals at room and liquid helium temperatures, and magnetic anisotropy constants K₁ and K₂ calculated. Precise crystal structures of substituted compounds have been determined by X-ray diffraction, and cation distribution on all crystallographic sites refined. Magnetic structures of (Ru-Co)_x and (Ir-Zn)_x substituted hexaferrites with x = 0.3 and 0.8 have been determined by using neutron diffraction. According to these studies, magnetic anisotropy change is correlated with the substitution of A for Fe cations on bipyramidal and octahedral sites in the R block, and Me for Fe cations on tetrahedral and bipyramidal sites. Magnetic moments rotate progressively with x from the c-axis to the (a, b) plane.