ABSTRACT. Measured replay pukes, recorded on Metal Evaporated tape, show a strong asymmetry and dependence on the direction of tape movement. It is found that pulse height and pulse width are unequal for both directions of tape movement. This is attributed to the non longitudinal easy-axis direction which causes differences in headtape geometry for both directions resulting in a different transition width. A simulation model is proposed. The differences in pulse asymmetry and pulse width between both directions of tape movement are very well reproduced by this model. From X-ray diffraction measurements and the results of the simulations it is concluded that not the columns but the crystallites act as magnetic entities for this kind of tape.

Thin films of the perpendicular recording material CO IOOx Cr x (x = 17-23) were ion beam sputtered from alloy targets. The saturation magnetization and uniaxial anisotropy constant, as a function of temperature, both show a strong dependence on the substrate temperature during deposition Ts, indicating composition shifts which increase with Ts. The films have a columnar structure on a scale which does not depend on Ts in contrast to the grain size. From studies of the phase relations in bulk Co-Cr alloys and diffusion couples it is concluded that phase separation of ordered Co-Cr phases does not occur at high Ts. Instead the composition shifts and the grain refinement at higher Ts are proposed to be caused by oxygen gettering and oxide trapping during film growth.

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