Preparation and properties of crystal-oriented ferroxplana samples

Samples of the hexagonal ferroxplana materials, with a preferential plane for the magnetization, show an increased resonant frequency compared to samples of cubic ferrites with the same permeability. It appeared possible to use the large stiffness for rotation of the magnetization out of the preferential plane, in order to orientate the single crystal particles of a ferroxplana powder in a magnetic field. In this way samples with two different textures have been obtained. In one case the basal planes of the crystals have one direction more or less in common (fan texture); in the other case all basal planes lie more or less parallel to each other (foliate texture). In both cases the permeability is appreciably increased, while the resonant frequency is only slightly decreased. Permeabilities of 56 at 90 Mc/sec and 28 at 230 Mc/sec, both for tanδ=0.1, have been found. This large increase in permeability is caused mainly by an elimination of the effect of the anisotropic permeability of the crystals.