Overwrite and track edges in high-density tape recording - simulations and analysis

In this work the study of digital information storage on tape takes a central place. Hereby a current is applied to the inductive head, which generates a magnetic field at the head gap. Depending on the field direction, the medium can be magnetized in a direction (anti)parallel to the tape motion. In this way it becomes possible to write a specific signal on a magnetic coating. The tendency to realize higher information storage densities in a smaller area, draws the attention of system designers strongly at the study of the parameters influencing the write and read process. In this thesis we more closely look at these parameters. The emphasis lies on the overwrite behavior. Herewith is meant the extent to which residues of the original signals, after it has been overwritten with new information, influence the new information. Further, track edges of partially overwritten tracks on a particulate and thin-film tapes have been studied. This analysis is of high importance for the understanding of the recording behavior at high track density. A limiting factor for high track density is the bad track edge definition. The thesis consists of two parts. The first part gives a recapitulation of the experimental and theoretical environment around which this research took place. In the second part (chapter 5 – chapter 9) the results are shown. After a general introduction a treatise is given of most important facets of recording theory. This is followed by a description of the experimental methods in chapter 3. Chapter 4 gives a synopsis of the model used, which is equipped with a hysteresis model, called the Moving-Preisach Stoner-Wohlfarth model. In chapter 5 a particulate tape is analyzed with respect to signal output and overwrite behavior. Modulation of the new signal (l = 0.5 mm) by the original signal and residual signals in deeper layers of the magnetic coating are responsible for the overwrite behavior. These two effects are closely linked to each other. Applying larger currents to the inductive head result in larger write fields, which penetrate the magnetic coating more deeply. This effects in improvement of overwrite behavior. The wavelength dependence on overwrite shows that long wavelengths are more difficult to overwrite than short ones. Reduction of the (magnetic) coating thickness improves also the overwrite behavior. Furthermore, by modeling the influences of particle orientation, switching field distribution, coercivity, magnetization in the magnetic coating, the head-medium spacing, and gap length have been studied.