Particulate double-layer tape samples with magnetic underlayers have been investigated by performing magnetic recording measurements and by computer simulation. The presence of soft-magnetic underlayers resulted in decreased signal output and better overwrite behavior. Hard-magnetic underlayers showed the opposite result.

MFM images of tracks written in ME and MP tape have been obtained. The analysis of the images concentrated on the track edges. A track written with signals of 0.5μm wavelength overwrites a part of a track written with a wavelength of 1μm. The sharpness of the edges was derived from MFM results. It can be seen that the MP sample shows smaller changes in sharpness of the edge with an increasing write current than ME tape. In ME tape, the region between the λ=0.5μm and the λ=1μm parts of the track is much wider than the original λ=1μm edge.

Since the first experiments on magnetic recording by Valdemar Poulsen in 1898 the use of this technology has grown tremendously and magnetic storage is used in almost every home in the world. A special challenge was the recording of video signals which need a high bandwidth. In the 1950s, television broadcasts had started which created a need for storage in the broadcast world. The first broadcast recorder was the Quadruplex from Ampex in 1956. Later solutions were found for application in the consumer market. Better mechanics, magnetic tapes and recording heads allowed the mass production of a cheap consumer recorder. The size and weight decreased tremendously and portable camcorders are very common. Recording of broadcasts, video rental and home movies are now very popular. The factors which contributed to the maturing of this technology will be reviewed in this paper.

A thin MP tape is modeled to study the overwrite behavior as a function of increasing head field. For the simulation we use a moving-Preisach and Stoner–Wohlfarth hysteresis model which is implemented in a numerical recording model. A measurement at the optimum current of the overwrite ratio (OWR) shows a perfect reproduction of its value in the simulation. A layer-by-layer depth analysis is performed to investigate the origin of the residual signal. The model can also explain the decreasing trend of the OWR versus the head field.

DigaMaxTM thin film heads have been used with advanced tapes to estimate the performance improvement that is possible with respect to Co–γFe2O3 900Oe coercivity tape. The use of high sensitivity magneto-resistive read heads allows signal and media noise measurements at relatively low tape speeds with minimal interference from the electronics noise. This measurement method shows that although the absolute signal from advanced tapes has increased tremendously in recent years, the signal-to-media noise ratio has increased at a much smaller rate. Nevertheless, the best commercial metal evaporated tape of today shows a 4–5dB improvement in signal-to-noise ratio when compared to 900Oe tape.

The performance of ME tape has been studied by assuming a certain morphology of the magnetic layer. The effects of a non-uniform magnetization throughout the depth and an easy-axis out-of-plane are studied and their influence on the recording behavior are investigated. For this purpose a self-consistent recording model is used, in which a Moving-Preisach Stoner–Wohlfarth hysteresis model is implemented. Decreasing the magnetization from the top to the bottom layer could possibly improve the recording characteristics.

Digital tape recording systems show the same trend as hard-disk drives: a large increase of storage density with time. The use of advanced media and highly sensitive thin-film heads with magnetoresistive (MR) readout will increase the storage density dramatically. Key improvements are narrower tracks, more sensitive MR elements attained by applying the giant magnetoresistance effect, high-saturation flux density pole materials, advanced metal powder tape, intimate head-to-tape contact, and accurate tracking. By increasing the number of channels in the multitrack thin-film head, high data rates can be obtained as well. The basics of digital magnetic recording are discussed and a short historical overview is given of the Philips activities on thin-film heads for tape recording. An outlook on future improvements is given.

The multichannel servo writer and the data read/write heads of the new DigaMaxTM tape storage system are discussed. These heads enable a storage capacity of 13 GB (uncompressed) on 300 m of 72 kA/m tape using prerecorded buried servo information for dynamic track following during reading and writing of data

Differences between the recording characteristics of thin MP and ME tape are studied. The effect of the thickness reduction of MP tape is also investigated. When thin MP tape (with thickness 140 nm) is compared with ME tape (with thickness 150 nm), we observe a better signal and overwrite response for the ME tape. Through simulations the influence of an easy axis out-of-plane and a different reversal mechanism in ME tape is related to overwrite behavior

Quantitative comparisons of experiments and the predictions of various models of overwrite phenomena are presented; For the range of wavelengths (/spl lambda/) and write current amplitudes (I) used in this work we find that the residual signals present after overwrite can be described within the context of a single physical process which is described in the rewriting model. The rewriting model is found to give rise to both the overwrite induced bit-shift, and the depth-of-recording phenomena which we observe. The experimental results indicate that variations in the head properties (efficiency and head field gradient) do not contribute significantly to the residual signals following overwrite, for the head and frequency range we used. Finally, we present the first spatial-domain measurements of spatial phase sensitive overwrite induced bit-shift in thick media.

Thin metallic films are the first choice for media in advanced rigid disk systems. For helical scan tape recorders thin metal films have become more important. The high signal-to-noise ratio per unit of track width allows very high densities. The preparation techniques and materials properties of the thin-film coating of metal evaporated (ME) are described. Important aspects are the size of the grains, the geometry of the columnar structure and the associated anisotropy. The consequences for the recording process are explained. Tribological and corrosion properties also help to determine the usefulness of a recording tape. Corrosion, wear, protection layers and lubricating organic films are briefly discussed.

The influence of an offset in the write current on the recording process in metal particle (MP) and metal evaporated (ME) tapes has been studied. The resulting bit-shift (the leading order effect) was measured experimentally using two techniques. The influence of the offset was also studied using numerical simulations of the recording process.

Numerical simulations of the recording performance of metal particle (MP) tapes as a function of improvements in the geometric (head-to-tape distance and tape thickness) and magnetic properties (saturation magnetization and coercivity) of the tapes have been performed. For the tapes considered significant improvements are possible. A total improvement relative to existing MP tapes of 6.9 dB at a wavelength of 0.5 μm is predicted.