Saturation magnetic recording process

This review of the saturation magnetic recording process is tutorial in approach. The emphasis throughout is on the development of intuitive understanding as well as the development of a first-order analysis (good to 10-20 percent) of the process. By means of treating two different functional approximations to the magnetization distribution in the medium, linear and arctangent, it is shown that the peak output voltage and half-amplitude pulse width of a transition are nearly independent of the distribution. Thus good estimates of these important system parameters may be made without reliance upon a specific model. It is made apparent that head-to-medium spacing and effective-medium thickness are of dominant importance in system density considerations.     

The WRITE process in magnetic recording

An extension of an earlier model of the WRITE process in saturation recording that accounts for internal fields due to magnetization divergence in the recording medium is presented. It is shown that the initial condition of the medium determines the internal field distribution during WRITE and may lead to appreciable peak shift and WRITE over modulation. The special case of two successive reversals of magnetization for a dc biased recording medium is considered in detail. System design criteria for optimization of the recording medium parameters, the head pole gap, and the WRITE time constant are presented for a system where the remaining parameters are constrained. Calculation for the initial and quiescent magnetization and internal field and the expected signal trace, in addition to experimental data, are presented for an out-of-contact drum system employing a NiZn ferrite WRITE-READ head and a CoNiP plating.     

Geometric effects in the magnetic recording process

A simplified view of magnetic recording is presented in which the effect of head-medium geometry is clearly exhibited. The model is applied to contact recording with a ring head on thick particulate media. Demagnetization fields are neglected and identical particles with angularly invariant switching fields are considered with various orientation distributions in the recording plane. For all orientation distributions symmetric about the longitudinal direction the longitudinal magnetization component vanishes at the head surface and increases with depth into the medium. Conversely, the vertical component is maximum at the head surface and decreases with depth. The resulting recording spectra therefore have greater magnitudes for vertically well-oriented particles and isotropic distributions of particles with biaxial symmetry. At short wavelengths these distributions give approximately 5 dB more output than longitudinally well-oriented media. The depth variation of longitudinal magnetization also provides one explanation for the peak in the short wavelength input-output curve measured on longitudinal media. These conclusions are expected to be dependent on the assumed angular variation of the particle nucleation field.     

Electrographic magnetic stylus recording; A high speed non-impact magnetic printing process

An electrographic magnetic printing process is described which uses magnetically attractable and electronically conductive dry toner material deposited directly onto a dielectric layer in response to electronic current flow from one member of an array of magnetically permeable styli. The imaging process is extremely flexible in imaging speed, dot/mm resolution, continuous grey scale, and materials.     

Models of the longitudinal digital magnetic recording process in thin films

A review of the various mathematical models of the longitudinal recording process in thin-film recording media is given. One of the main focuses of the review is on the arctangent theories of recording, and these are discussed in terms of both their successes and their failures. More recent work shows an increasing trend towards determining the nature of the recorded distributions directly from the calculations.<>     

Perpendicular magnetic recording

This paper describes the recent studies for the magnetic head, the medium and the recording properties on a new perpendicular magnetic recording system. The complemental features between the perpendicular and the longitudinal recording are discussed to establish an efficient magnetic recording system. Superior response in the amplitude and the peak shift characteristics for a digital signal proves that the perpendicular magnetization mode is basically free from the recording demagnetization in high densities and the maximum density has been limited merely by the resolution of the reproducing head. Significant improvement for the recording and the reproducing sensitivities of a perpendicular head has been made by using a composite anisotropy medium composed by double layers of Fe-Ni and Co-Cr thin films.     

Grain size effects on magnetic properties and core process of recording head Ferrites

A study has been made which correlates grain size with magnetic properties so that the proper range of grain size in ferrite materials can be determined for recording head applications. The effects of Ni-Zn and Mn-Zn ferrite grain size on 1) initial permeability, 2)B-Hloop, 3) density of ferrites, and 4) core processing, e.g., lapping and glass bonding, are described. Both experimental results and published research indicate that highly densified ferrites having larger grains are desirable for recording head applications. ASTM grain size Nos. 8-9 are therefore recommended for Ni-Zn ferrite R/W heads.     

Integrated magnetic recording heads

A new type of integrated magnetic recording head has been developed. The head is made completely from thin films by vacuum deposition through a mask. This technology enables us to make many heads in one vacuum cycle. A special study has been carried out on the geometrical forms and on the anisotropic magnetic material. The demagnetizing fields require that we make magnetostatic coupling layers for each magnetic leg of the head. Also, the results indicate that the heads can be used for writing and reading.     

Switching time of single magnetic particle and maximum recording frequency of perpendicular magnetic recording

We investigated the switching time of a magnetic particle-which may impose limits on magnetic recording frequency-by computer simulation. We found that the difference in switching time between low and high temperatures decreases with increasing the angle /spl xi/ between the applied field and the easy direction, and scarcely changes with temperature if the angle is larger than a few degrees. This can be explained by considering the energy contour and locus of magnetization in switching. The switching times derived by using divided models, in which the particle is divided into 2/spl times/2/spl times/2 or 4/spl times/4/spl times/4 cells, are smaller than those derived by using an undivided model. But the difference between the switching times derived with the divided and undivided models is less than 1% if the angle /spl xi/ is larger than 1/spl deg/. We derived equations to express the switching times of the particle for the divided models at /spl xi/=0, and we used the equations to estimate the maximum recording frequency in perpendicular recording.     

Possibilities of perpendicular magnetic recording

The potential of perpendicular magnetic recording using a single-pole head and a double-layered medium has been investigated theoretically by computer analysis and compared with that of longitudinal magnetic recording. In conventional longitudinal recording, a recording demagnetizing loss due to the change of magnetization mode from semicircular to circular shapes occurs with increasing recording level at high bit density. In perpendicular magnetic recording, the perpendicular magnetization mode is maintained regardless of recording level even at an extremely high bit density of 571 kFRPI. This indicates that the perpendicular recording medium has a very high recording resolution, where a single bit size approaches several diameters of the microcrystalline particles of the Co-Cr layer. An ultrahigh density at which the recording area for 1 bit will reach 1 μ² at present and 500 Å₂ in future should be possible     

Barium ferrite magnetic recording media

Barium ferrite particulate media have generated a lot of interest for advanced magnetic recording applications because they offer the potential to combine high recording densities with relatively low manufacturing cost. They consist of small (sub-tenth micron) plateletshaped particles with competing orthogonal anisotropies (crystalline and shape) of comparable magnitude. These anisotropies, along with the quasi-perpendicular characteristics of the barium ferrite coatings impart to them many subtle and surprising properties, requiring a careful and judicious choice of parameters for each application. The choices include the aspect ratio of the particles, their coercivity, the particle-to-binder loading, and the degree and direction of magnetic orientation. The problem areas include dispersion and orientation of the particles, overwrite characteristics of the coatings, thermal coefficients of the magnetic parameters and maintaining media coercivities at moderate levels. I this paper, we discuss the effect of the particle and coating parameters on the ensuing magnetic and recording properties of the media, and the types of choices that should be made to minimize the impact of some of the potential problems mentioned above.     

Humidity effects in magnetic recording

Humidity effects in magnetic recording are reviewed. We highlight the progress made toward quantifying water adsorption on lubricated overcoats, leading up to the present understanding of humidity effects on magnetic recording tribology. Recently, it was found that moisture is also absorbed by hygroscopic atmospheric contaminants to form liquid nanodroplets on the overcoat. Rheological and dielectric measurements were performed to investigate the properties of the nanodroplets. Solutions of 1 wt% to 10 wt% water in Ztetraol are gel like and highly viscous. Dissolved water increases the low-frequency permittivity and conductivity, and shortens the dielectric relaxation time, relative to dry lubricant.     

Co-modified pigments in magnetic recording

This paper surveys the physical properties and storage performance of the class of 650 Oe pigments, which are presently mainly being used for home video, high-quality audio and will in the future be intended for high-density digital storage applications. The temperature dependence of coercivity, the change of coercivity by annealing of a sample in a magnetic field and various aspects of the switching field distribution are shown up in detail. The different data are discussed within a newly developed comprehensive model of Co-modified particles. The model correlates morphological and chemical data with physical properties and storage performance, especially print-through data and erasability effects.     

Patterning of FePt for magnetic recording

Higher areal density for magnetic recording is needed to provide larger storage capacities on harddisk drives. However, as the recording bit size of traditional magnetic recording materials (such as Co/Cr) approaches 10 nm, the magnetic direction of each recording bit would become unstable at room temperature due to thermal fluctuation. To solve this problem, efforts have been made using two methods: one method is to replace the disk media with new materials possessing higher magnetic anisotropy which would lead to better thermal stability; and the second one is to employ different configurations for the recording layer. FePt with patterned media configuration is a combination of these two methods. In this paper we review some novel and interesting methods of patterning FePt for magnetic recording, including thermal patterning, self-assembly patterning, and lithography patterning.     

Hygroscopic properties of magnetic recording tape

Relative humidity has been recognized as an important environmental factor in many head-tape interface phenomena such as headwear, friction, staining, and tape shed. Accordingly, the relative humidity is usually specified in many applications of tape use, especially when tape recorders are enclosed in hermetically sealed cases. Normally, the relative humidity is believed regulated by humidification of the fill gas to the specification relative humidity. However, this study demonstrates that the internal relative humidity in a sealed case is completely controlled by the time-dependence of the hygroscopic properties of the pack of magnetic recording tape. Procedures for the humidity conditioning of sealed cases must be established on the basis of the tapes' hygroscopic properties, and not on humidification of the fill gas. Without taking the tape into account, the final, stabilized, relative humidity can be significantly different from the specification requirement. Additionally, this same study finds differences in the hygroscopic properties of the same brand of tape, which apparently results from aging, and which may have significance on the long-term humidity-regulating behavior in a sealed case, and on the occurrence of head-tape interface phenomena from the long-term use of the tape. This article presents results on the basic hygroscopic properties of tape, its humidity-regulating behavior in a sealed case, and includes a theoretical commentary on the relative humidity dependence of head-wear by tape.     

Wavelength response of perpendicular magnetic recording

From the measurements of the surface field of a recording medium, it was obtained that an almost ideal step change distribution of magnetization is formed in perpendicular recording for digital signals. The fact represents that the upper limit of usable recording density is determined only by the resolution of a reproducing head. Therefore, the reproduction by a perpendicular head was successfully analyzed by using the reciprocity theorem. By introducing thickness loss of main pole of the head, the satisfactory coincidence was obtained between the calculated and the measured results in the wavelength response even at the densities of more than 150 kMRPI. In reproducing process, the magnetic interaction between the main pole and the medium acts so as to decrease the effective spacing between them.     

Optimizing tape‐burnishing/wiping process of magnetic recording media through Taguchi method

For the ever‐increasing recording density in hard disk drives, ultra‐low gliding height media are required. It is an immense challenge for the tape‐burnishing/wiping process of media to reduce the asperities effectively and efficiently while no scratches occur. The purpose of this paper is to characterize and then optimize the tape‐burnishing/wiping process as so to minimize the asperities without leaving any scratches on the media surface. A Taguchi experiment design method is adopted to analyze the data and acquire an optimal level combination of process parameters. The resulting optimal combination is practically implemented in tape‐burnishing/wiping the several magnetic recording media, which reveals that the average pass ratio of 5 nm glide avalanche testing increases nearly doubly to a level of 96%. Copyright © 2008 John Wiley & Sons, Ltd.     

超高密度磁存储的展望

磁性存储是最常用的海量存储技术,其记录密度越来越高,发展也越来越快。本文通过对信息记录、读出和存储三个过程的分析,对比了硬磁盘记录、垂直磁记录和磁光记录的优缺点,指出了采用垂直记录模式、非晶结构合金薄膜或铁氧体薄膜介质是实现超高密记录的方向,光辅助磁记录是很有希望的记录技术。同时,还指出量子磁盘技术是未来高密记录的方向。