Aligned Co2Z hexagonal ferrite fibers

The hexagonal ferrites, also know as hexaferrites, have become massively important materials commercially and technologically, accounting for the bulk of the total magnetic materials manufactured globally, and they have a multitude of uses and applications. They all have a magnetocrystalline anisotropy; that is the induced magnetization has a preferred orientation within the crystal structure. They can be divided into two main groups: those with an easy axis of magnetization, the uniaxial hexaferrites, and those with an easy plane (or cone) of magnetization, known as the ferroxplana or hexaplana ferrites. There is currently increasing interest in composite materials containing hexaferrite fibers. It had been predicted that properties such as thermal and electrical conductivity, and magnetic, electrical and optical behavior will be enhanced in material in fibrous form. This is because a continuous fine fiber can be considered as effectively one-dimensional, and it does not behave as a homogeneously distributed solid. Although the intrinsic magnetization of the material is unaffected, the effective magnetization of an aligned fiber sample should be greater when a field is applied parallel with fiber alignment compared to when applied perpendicularly to fiber alignment. This feature was first demonstrated by the author for aligned hexaferrite fibers in 2006, who was also the first to synthesize fibers of BaM, SrM, Co2Y, Co2Z, Co2W, Co2X and Co2U hexaferrites, as micron-scale (3-10 mm) continuous fibers in both random and aligned blankets. The magnetic properties of aligned Co2Z (Ba3Co 2Fe24O41) hexaferrite microfibers are presented in this paper. It is shown that unlike with the uniaxial M ferrite fibers, the ferroxplana Co2Z ferrite fibers do not shown any significant alignment affects with direction of applied field. They have high Ms values in all orientations. This is attributed to the microstructure of these fibers, in which the hexagonal plates are stacked and oriented parallel to the fiber axis. This appears to counteract the expected effects of fiber alignment on measured Ms values.