Particulate Magnetic Media Research Articles

Analysis of AC type magnetization processes in particulate recording media

This paper presents an experimental and theoretical analysis of a number of AC-type magnetization processes similar to those encountered in magnetic recording (AC-biased, DC-biased, partial anhysteresis) on particulate magnetic media. The modeling of these magnetization processes was performed with a scalar generalized moving Preisach (GMP) model. The experimental results obtained for a SVHS tape sample are compared with the theoretical ones. A robust identification method for the parameters in the GMP model was used. This method exploits the main static magnetization curves (major hysteresis loop, isothermal remanent magnetization, DC demagnetization, first magnetization curve), and the integral generalized /spl Delta/M curve, which is sensitive to the value of the moving parameter and to the standard deviation of the interaction field distribution. The agreement between the simulated and measured curves is discussed.

Behaviour of lubricant migration in particulate magnetic recording media

The effect of the recovery speed of lubricant on the durability of particulate magnetic media is presented in this paper. The use of newly synthesized perfluoropolyethers (PEPEs) in particulate media allows us to evaluate the amount of surface lubricant and the migration by X-ray photoelectron spectroscopy (XPS). The migration rate of the lubricant is evaluated as the change of the XPS peak area after argon etching to remove the surface lubricant. A recovery speed depends on the kind of lubricant and way of coating. Furthermore, lubricant of higher recovery speed has better stability of friction coefficient.

A study of the mechanical and magnetic performance of metal evaporated tape

There are substantial gains to be made in terms of recording density and frequency response if the particulate magnetic media is replaced by a continuous thin metal film. Very thin metal evaporated coatings applied to thin, flexible substrates present a unique set of contact problems, particularly when the recording head is in intimate contact with the tape and in helical scan formats. Some of these contact problems have been addressed in this work where we report on the identification of specific wear mechanism of metal evaporated tape. Mechanical, physical and chemical changes in the surface of the two commercially available ME tapes have been correlated to recording error and signal degradation measurements.

Delta-H plot evaluation of remanence behavior in barium ferrite tapes and disks

Remanence studies in recent years have used the characteristics of the Henkel plot and the delta-M plot in the interpretation of interaction field effects in particulate magnetic media. Studies of these two plots in ordered BaFe coatings, however, indicate that both plots give inadequate description of interaction field effects. An alternative to the delta-M plot is the delta-H plot in which, essentially, the (normalized) susceptibility curves for the isothermal remagnetization and dc demagnetization processes are differenced horizontally (rather than vertically as in the delta-M plot). It is shown here that the delta-H plot is a more direct way of examining the interaction fields. Simulated delta-H plots are presented based on a recent mean field model by Che and Bertram and are compared with measurements made on oriented BaFe coatings.

Particulate Magnetic Media Contamination: Large Defects

Participate magnetic media is widely used throughout the computer industry for data storage. Particle contamination is a major source for head crashes in magnetic disk drives. Bit size, track width and flying heights are decreasing because of the demands for greater storage density. As a result, the interfacial phenomena between the head and the disk are becoming critical. Particles generated during the operation of a magnetic disk drive or introduced through the defects in the filtering system, can cause a Head/Disk Interference (HDI) and/or result in a total system failure due to a head crash.Interaction between the head and the particle becomes responsible for HDI or head crashes. The HDI occur either from the head impacting and shattering the particle as shown in Figure 1 or the particle is dragged across the disk surface by the head as shown in Figure 2. The particle, marked by the arrow, in Figure 2 has been pushed into the substrate.

Sputtered carbon on particulate media

The application of a thin, amorphous, carbon film to the surface of particulate magnetic media has been demonstrated as an alternative to liquid lubrication, eliminating the problems such as stiction, lube retention, and loss associated with traditional liquid lubricants. It also eliminates the necessity of nonmagnetic, load-bearing, alumina particles. The carbon has been deposited onto disks by DC magnetron sputtering from a graphite target. Extensive functional tests, including start/stop, stiction, accelerated wear, and pin-on-disk, have shown that carbon overcoat performs well on various types of particulate media and under a wide range of environmental conditions. The surface topography and chemistry of the particulate media uniquely enhance the tribological behavior of sputtered carbon on its surface, unlike ultrasmooth, thin-film magnetic media with carbon overcoat, which have been shown to be very sensitive to environmental conditions. >

Temperature dependence of magnetization time decay in particulate magnetic media (abstract)

We report on magnetization time decay (MTD) data on several commercial and experimental tapes, γ-Fe2O3 (as a function of packing fraction), Co-doped γ-Fe2O3, and CrO2, measured from 2 to 400 K between 1 s and 104 s. We have found that the decay of the magnetization with time, for a given temperature, does not follow a simple log t relation. At each temperature we analyze our data with an empirical model,1 which relates values of coercive field, Hc, obtained with a 60-Hz B-H looper to that measured with a slow VSM field cycle (i.e., over ten orders of magnitude of time). Particular emphasis will be given to the nature of the MTD in these samples when extrapolated to zero temperature. These data will be compared to that previously reported,2 and the role of possible nonthermal mechanisms will be discussed.

Switching behaviour of interacting magnetic particles

The magnetostatic properties of particulate magnetic media depend strongly on the packing density because of the magnetic interactions of the particles. To investigate the influence of these interactions we considered two models. One was a dipole model consisting of anisotropic dipoles and dealing with only one component of the magnetic moment. The other model consisted of two interacting Stoner-Wohlfarth particles, where the magnetic moments might rotate. We observed that in the latter model the coercive force decreases under practical conditions with the strength of the interaction, while in the first model it increases.