Recording characteristics of electroless-plated perpendicularrecording flexible disks with a perpendicular head

Perpendicular magnetic recording using a main-pole-driven perpendicular head was tested using electroless-plated flexible disks. Soft magnetic NiFeP films, also produced by electroless plating, were used as an underlayer of a perpendicular recording medium in this test. Two types of flexible double-layer media, composed of an electrodeless-plated CoNiReP film with two types of NiFeP underlayers with a coercivity of 2 and 5.5 Oe, were fabricated, and their recording characteristics were measured. A recording density value of 75 kFRPI was obtained for the medium with the softer magnetic 2-Oe underlayer, about twice as high a value as that for the medium with the 5.5-Oe underlayer     

Kerr effect microscopy imaging of recorded domains on perpendicularmagnetic recording media

Recorded domains on perpendicular recording double-layer media were imaged by magnetooptical Kerr effect microscopy. The reversal domains were observed at the edge of tracks by a head whose leading pole is wider than its trailing pole. It was found that the perpendicular magnetic field of a trailing pole overwrites the domains written by that of a leading pole     

Recording on perpendicular anisotropy media with ring heads

This paper reports experimental studies directed at the application of ring head structures to a perpendicular recording system. The media tested were sputter deposited films of CoCrTa alloys. Ferrite heads were studied, but the thin film head was chosen for evaluating roll-off, overwrite, and superposition. The data presented in the paper demonstrates the potential of high density recording with a single layer medium with perpendicular magnetic anistropy and a thin film head separated by 0.20 micrometers.     

Properties, preparation, advances and limitations of materials andmedia for perpendicular recording

The trends in perpendicular magnetic recording research are discussed, with emphasis on clarifying the trend of research on recording media, their materials, and head materials. Among numerous proposed perpendicular recording media materials, barium ferrite powder and evaporated Co-Cr films seem to lead in practical applications, since their mass production seems to be very successful. There still exist crucial points in their development. However, improvements are continuously taking place. Other candidate perpendicular recording media for a device which has a ring head are also discussed. It is concluded that, for future high-density magnetic recording, utilizing fully the perpendicular component of media magnetization will furnish the key to success     

Perpendicular magnetic recording with a composite anisotropy film

For a recently proposed perpendicular recording system, a composite anisotropy medium has been developed to improve the recording sensitivity of the perpendicular recording head. The medium is composed of a Fe-Ni soft magnetic film and a Co-Cr perpendicular anisotropy film, which are successively deposited on a base by an r. f. sputtering. By using the new double layer medium, an extremely high recording sensitivity could be obtained, compared with the single layer Co-Cr medium. The recording current needed to saturate the double layer film decreased to one-tenth of that for the single layer Co-Cr film. Although the Fe-Ni layer was soft magnetic material, neither deterioration of the frequency response nor peak shift was observed for the double layer film. The reproduction with a perpendicular head was also investigated, and a high output voltage and a high signal-to-noise ratio were obtained.     

Media for high density magnetic recording

Longitudinal recording is limited at high bit densities by recording demagnetization, self-demagnetization, and adjacent-bit demagnetization, which occur during the writing-demagnetization processes. To minimize these adverse effects it becomes necessary to resort to extreme scaling of the media parameters and their thickness, with the consequence of greatly increasing the difficulty of fabrication and the cost of such optimized media. Pure perpendicular recording circumvents these writing and demagnetization problems because of the strong head coupling of a single pole head with a double layer medium, positive interaction between adjacent bits, and low self-demagnetization at high bit densities. Therefore, it does not require any extreme scaling of the media magnetic parameters and their thickness. Of great interest, at least for the next several years, are the quasi-perpendicular particulate media which can support perpendicular magnetization. These include the isotropic, high-squareness media, and oriented perpendicular media employing particles with uniaxial crystalline or shape anisotropies. The attractiveness of these media derives from their excellent recording performance and from the fact that they preserve the existing head/media interface and they utilize existing coating facilities which should reflect favorably on their cost. In this paper the advantages and disadvantages of the various media under development for high density magnetic recording are compared, and predictions are made for their potential application in future systems.     

The effect of magnetic interaction between medium and head on perpendicular magnetic recording characteristics

The high density recording characteristics of perpendicular magnetic recording using a single-pole head are affected by the magnetic interaction between the medium and the head. By decreasing the relative thickness of the Co-Cr layer in the double-layer medium to that of the main-pole of the head, and increasing the saturation magnetization of the Co-Cr layer, the high density recording characteristics are enhanced. When requisite conditions are realized, the reproduced voltage vs. bit density characteristics are improved considerably for a thinner main-pole of the single-pole head.     

Extremely high bit density recording with single-pole perpendicular head

Since perpendicular magnetic recording is free from recording demagnetization, high-density recording up to the intrinsic limit of a recording medium is possible. This prediction was verified experimentally in a flexible disk system using a single-pole head and a Co-Cr/Ni-Fe double-layer medium. We could record and reproduce signals up to 680KFRPI. The recording bit length at the highest density was of the order of the Co-Cr columnar diameter.     

High-energy Co-Cr thin films sputtered on glass disks forperpendicular recording

The authors have developed high-energy Co-Cr thin-film perpendicular recording media for rigid disks. They obtained high perpendicular coercivity (Hc⊥) exceeding 2000 Oe with Co-Cr films sputtered on glass disks. They examined recording characteristics obtained with double-layered media and single-pole heads. Readout voltages were proportional to Hc⊥ up to 2000 Oe and not dependent on saturation magnetization. The authors explain the experimental results using the hysteresis curve of the Co-Cr film and the permeance factor determined by the magnetic reluctance of the head and medium. Using a magnetic circuit model, they clarify the effect of the difference in the operating point on the hysteresis curves of rigid- and flexible-disk systems     

Fundamental properties of perpendicular magnetic recording

A two dimensional computer simulation model of the magnetic recording process has been, developed to assess the fundamental properties of perpendicular magnetic recording. It was found that vertical anisotropy media are well suited to abrupt and closely spaced magnetic transitions. The demagnetizing fields support short transitions in the perpendicular mode as opposed to degrading transitions in the longitudinal mode. However, gapped heads may have difficulty in delivering high intensity vertical fields to saturate the medium. Novel write head designs might be required.     

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.     

FePt纳米薄膜研究进展

由于FePt在超高密度磁存储材料方面的广阔应用前景及其局限性,研究人员对FePT薄膜进行了大量的研究及改性.根据国外近期在此领域的研究现状,综述了单相、复相及掺杂FePt薄膜的制备以及对结构和性质的影响.复相或掺杂主要是通过结构的改变来降低L10晶相转变温度和FePt颗粒的大小,通过其耦合作用来影响FePt薄膜的磁学性能,使其成为超高密度存储器材料.     

Theory of playback process with soft magnetic underlayer

Based on the Tsuboi-Fushida-Wallace spacing loss law, reciprocity principle, and the principle of an image plane, a two-dimensional, head independent theory of the playback process has been developed for perpendicular magnetic recording (PMR) media with a soft magnetic underlayer (SMUL). An assumption that the reversible magnetic permeability of the recording media is equal to one gives results in a simple form. The article, while not addressing the effect of underlayer on write performances, demonstrates complications caused by the presence of the underlayer during readback.     

Structure, morphology and magnetic properties of Fe-B-Si-Nb glassy alloy thin film prepared by a pulsed laser deposition method

With the aim of applying to a soft magnetic underlayer of the double-layered perpendicular magnetic recording media, an Fe_74.9B_17.5Si_2.5Nb_5.1 alloy thin film was fabricated on Si substrate by a pulsed laser deposition method. The Fe-based alloy thin film of 200 nm in thickness was confirmed as a glassy structure. The thermal properties of the thin film have similar features to those for the melt-spun glassy alloy ribbon. The glassy alloy thin film exhibits good soft magnetic properties, i.e., high B_s of 1.2 T and in-plane low H_c of 134 A/m. The Fe-B-Si-Nb glassy alloy thin film is expected to be suitable for the soft magnetic underlayer material in the double-layered perpendicular magnetic recording media.     

Spectral response nulls for single-pole heads in perpendicularrecording

This letter discusses the dependence of the nulls in the spectral response function of a single-pole head, used in perpendicular magnetic recording with a double-layer medium, upon the pole thickness and the distance between the pole and the underlayer. Exact results from a two-dimensional model are used to produce approximate but accurate relationships, and are compared with previously published theoretical and experimental results where full data are available     

Challenges in the practical implementation of perpendicularmagnetic recording

The storing of recorded bits in a perpendicular orientation holds great promise for high linear density recording systems. However, the most common embodiment of perpendicular recording (the probe head/double layer media) has several unresolved issues complicating its integration into commercial disk drives. The major issues include media relaxation, head induced media erasure, resolution limitations due to head-to-underlayer spacing constraints, and extreme sensitivity to stray magnetics fields, which are complex and highly interrelated. It is concluded that the realization of perpendicular recording in commercial disk drives will require new transducer and media designs that solve these problems     

Magnetization transitions obtained by deconvolution of measured replay pulses in perpendicular magnetic recording

Magnetization transitions in perpendicular magnetic recording have been calculated from measured replay pulses by a deconvolution algorithm using an analytical expression for the field of a probe head (PH). The transitions appear to be asymmetric whereby a pronounced magnetization peak occurs whose shape depends on the medium coercivity. For the experiments double layer media with double sided probe heads have been used. For the deconvolution only perpendicular head field and medium magnetization components are considered.     

FePtAg-C纳米颗粒薄膜的制备及表征

采用磁控溅射法在硅基片上生长FePt纳米颗粒薄膜。在硅片表面生长MgO籽层用来引发FePt合金薄膜的fct织构,加入C来减小其颗粒尺寸,加入Ag来增强其L10有序度。采用X射线衍射仪（XRD）、超导量子干涉仪（SQUID）和高分辨率透射电镜（TEM）对FePt薄膜进行表征。结果表明制备的薄膜样品具有优良的L10相结构,其M-H曲线表明方形度很好,垂直矫顽力HC有2467 kA/m,颗粒大小为10.4 nm。该薄膜非常适合用做下一代高密度磁存储媒质,可有效提高信息存储密度。     

Comparison of reproduction performance of a single pole head and a ring head

The reproduction pulse amplitude of a single pole head from double-layer perpendicular media has been analyzed. We derived an analytic expression to relate the pulse amplitude to the head and medium parameters. Experimental data are also presented to verify the calculated results. The reproduction performances of a single pole head and a ring head are theoretically compared and found to be comparable when both are normalized to the same head inductance.     

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