Double-layered Media Research Articles

Magnetic Recording Characteristics of Perpendicular Media with a Thin Soft Backlayer Using Merged MR Heads

The recording characteristics of single- and double-layer perpendicular media without and with a thin soft magnetic backlayer were investigated by using merged MR heads. In single-layer media, even a thin soft back-layer with a thickness of 10 nm increased the low-density output and the overwrite property by nearly 4 dB at magnetic spacings of less than 47 nm. In double-layer media with a 10-nm-thick backlayer, no degradation of the recording density was observed.

Effect of Medium Thickness in Perpendicular Magnetic Recording Using a Double-Layered Medium

The effect of the medium thickness in perpendicular magnetic recording on double-layered media is discussed. It was found that the thickness of the medium significantly affected the recording capability of the medium. By improving the coercivity of medium, we obtained high flux density on the surface of a comparatively thick medium.

Double-Layer Perpendicular Recording Media using Fe-Si-Al underlayers

Double-layer media with single pole heads are the ideal way of perpendicular magnetic recording. However, unstableness of recorded magnetization originating from magnetic domains of underlayers have not been settled. We investigated signal stability of the media using NiFe underlayers and the media using FeSiAl underlayers, which take the diferent magnetization process from NiFe underlayers. The results show that the media using FeSiAl showed better stability of recorded magnetization than those using NiFe.

Fabrication and Recording Characteristics of a Single-Pole Flying Head

We fabricated a novel single-pole head on a flying slider for perpendicular magnetic recording. By using three film-conductors to energize a main pole at its end, a high recording sensitivity of 0.03 ATP-P and a very low inductance around 10 nH were obtained. A D50 value of 135 kFRPI was confirmed, almost the same at that of a bulk coil songle-pole head in sliding contact recording. This head provides an idea of a practical single-pole head for a double-layered perpendicular medium for high-frequency applications.

Off-Track Overwrite Characteristics of a Single-Pole Flying Head

A submicron track width of 0.4μm was observed by measuring an MFM image with a combination of a single-pole head and a perpendicular double-layered medium. Because of its sharp head field distribution, this combination is considered capable of obtaining a very narrow track-pitch. By measuring the off-track overwrite profiles with a thin-film single-pole flying head, we found that the erase band width was around 25 nm, which was acceptable for merged MR head and perpendicular double-layered medium.

Influence of a Single-Pole Head on Output-Time-Decay in Perpendicular Double-Layered Media

In measurements of time decay in perpendicular double-layered media, a large output decay was observed when a regular single-pole head was used for both writing and reading. Investigation of this phenomenon revealed that the demagnetization of the media was caused by the instability of the domain wall of the main pole film and stray field concentration by the main pole during the reading process. Several countermeasures were proposed.

Resolution of unshielded and shielded MR heads for perpendicular magnetic recording

To achieve the recording technology over 10 Gb/in 2, quite short bit cells have to be written and read probably by an MR head. The resolutions of unshielded and shielded MR heads were estimated for perpendicular and longitudinal recording. Moreover, we designed and fabricated some samples of the MR/Inductive heads that have been developed for perpendicular magnetic recording, and evaluated them with a double-layered medium. The shielded MR head offered high D50 of 170 kFRPI and high-density readback signal of 500 kFRPI. However, when the recorded bit length became shorter than the MR-to-shield gap, the shield had little effect and the output of the shielded head was no longer roughly equal to that of the unshielded head. Even unshielded MR head has good high-density recording characteristics in case of the combination with a perpendicular medium.

A Multitrack Coding Scheme Designed for Perpendicular Recording Using Double Layer Medium and MR Head

A new multitrack coding scheme is proposed as a preferable use in perpendicular recording using a double layer medium and an MR head. The coding uses combinations of three codes in 8 orthogonal codes based on Hadamard matrix elements. The new coding method has a high code rate and reliability because of the multilevel correlation detection due to simultaneous reading of three tracks. The performances are investigated by theoretical calculations, simulations and experiments.

Microspore Culture of Winter Oil Rapeseed (Brassica Napus): II. Embryo Conversion, Plant Regeneration and Double Haploid Production of Brassica Napus L.

ABSTRACTSomatic embryos obtained via microspore culture of Brassica napus have been used for study plant regeneration and double haploid production. Two mode of plant regeneration were observed: direct embryo germination and secondary adventitious buds formation. Different number of plants have been obtained for studied genotypes. Improved direct embryo development was achieved when ABA in concentration 10 μmol for 14 days at 15°C was applied. Plants were successfully colchicine treated in in vitro rooting stage by double layer media. Colchicine solution in 0.1% concentration added as a second layer for 24 hours was optimal for double haploid production and did not suppress significantly plant development. Colchicine treatment of pot plants by cuttings or roots delay 3–4 months seeds harvesting. Sufficient number of double haploid plants for breeding purposes have been obtained.

Quantification of Perpendicular Magnetic Recording with Double Layer Media

A quantitative calculation of the readback performance of shielded MR heads is performed for high density perpendicular magnetic recording, and compared with that from longitudinal recording. An analytical expression of the head field of the MR head with doule layer media is given to be used in a reciprocity calculation. Conditions to achieve a half-height pulse width, PW50' of 115 nm and 70 nm are presented. With these results and SNR estimations, issues of the read/write system to obtain areal densities of 20 Gbpsi and higher are discussed.

Optimum Write Head Structure for Perpendicular Magnetic Recording Focused on the Write Field

The optimum structure of a recording head for a double-layer perpendicular medium has been studied by calculating the head field and the stationary recorded magnetization with a magnetic recording simulation program. The perpendicular field gradient of the thin film ring head is the same shape as that of the Single Pole Type (SPT) head. However, because of the magnetic saturation of the medium under-layer, the field distribution of the thin film ring head changes drastically with the change of write current. A wider gap length reduces this change of the head field, therefore the wide gap thin film ring head is able to be used with a double-layer perpendicular medium. It is confirmed that the thin film coil type SPT head reduces the influence of the magnetic saturation of the medium under-layer and writes a sharp transition.

Perpendicular Magentic Recording using Single-pole Head

Perpendicular magnetic recording using a single-pole head and a double-layered medium is still keeping the champion data on the writable and readable highest linear bit densities over 500 kFCl. In this paper, the feature of perpendicular magnetic reording and the design principle of the heads and media, the hot data of the recording characteristics, the problems for developement, and the future of magnetic reording are decribed.

A comparison of culture methods for tobacco (Nicotiana tabacum) anthers

Three different anther culture methods for the South African tobacco cultivars C11 × WOSB and CDL 28 were tested. The yield of haploid plantlets produced using a solidified or double-layer medium was significantly higher than with the use of a liquid culture medium. The former two media showed no significant differences. Important considerations which must be taken into account when deciding on the optimum culture method for anther cultures are also discussed.

Thermal Relaxation in Perpendicular Recording with Single Pole Head and MR Head

Thermal relaxation is becoming more and more significant as bit sizes are decreased to achieve high recording density. In this paper a separate read and write system, replacing the low read sensitivity single-pole head with a MR reproducing head and a regular SPT writing head, was used for experiments to measure the reproduced output reduction in double-layered media. The influence of the single-pole writing head during the reproducing process is brought out. Then, some simulation results associated with a curling switching model are also discussed.

Write Characteristics of Simple Structured Single Pole Head

The write head design for a merged MR head needs to be optimized to obtain a good write performance for a perpendicular magnetic recording application. We fabricated a write-only single pole head with the simplified structure which consists of a main pole and a thin film coil without a return yoke. The write performance of the single pole head with double-layered media was evaluated by using an MR read head. The O/W value obtained was less than -35dB, and the PW50 value obtained from the differentiated curve of the readback waveform was 0.20μm. The small PW50 from the recorded bits attributes to the sharp magnetic transitions.

The solution of unsteady coupled electromechanical problems for multilayered media

A rigorous formulation of the unsteady coupled electromechanical problem of the interaction of a massive electrode with a multilayered piezoelectric medium is given, and a general formulation of a method of solving it is proposed. As an example the problem for a massive strip electrode, which interacts with a single-layer, double-layer and triple-layer piezoelectric medium with unsteady loading is considered. The effect of the electroelastic properties of different materials (classes 6 mm of the hexagonal system) on the displacement of the electrode and the potential is pointed out.

R/W Characteristics of Perpendicular Magnetic Recording

The read/write characteristics of a double-layered perpendicular magnetic recording medium were examined by using a combination of a single-pole-type write head and a magnetoresistive read head (SPT write / MR read), and a conventional merged ring type inductive / MR head (RT write / MR read). By differential equalization of the reproduced voltage, the STP/MR head combination had high density recording capability, compared with the RT/MR head. Bit error rate through PR(1) signal processing was evaluated for the SPT/MR head combination and the RT/MR head. It is clarified that bit error rate for the SPT/MR head combination and the RT/MR head. The bit error rate less than 10-6 at 3 Gb/inch2 was obtained for the SPT/MR head combination.

Effects of Improved Background Pressure on the Deposition of Co-Cr Perpendicular Anisotropy Films

The effects of improved background pressure on the deposition of Co-Cr perpendicular anisotropy films were investigated. To obtain a high vacuum, an aluminum alloy chamber was used, whose inside wall was subjected to the EL process ro reduce outgassing from the chamber. The background pressure reached 4×10-8 Torr after chamber baking. The pressure was changed by the addition of nitrogen to the atmosphere. In spite of the nitrogen addition, the percentage of H2O in the atmosphere was greater than that of N2. As a result, we were able to obtain a high perpendicular coercive force and a high crystallinity for the deposition of Co-Cr at a low background pressure. As regards the recording performance, a perpendicular double-layered medium with the Co-Cr recording layer deposited in a high vacuum showed larger output than one deposited in a low vacuum.

Bit Density Dependence of Thermal Relaxation in Perpendicular Magnetic Recording

Thermal relaxation in perpendicular double-layered media was examined by simulation and experiments, using a single-pole writing head and an MR flying head. A new FEM simulation with a curling switching model is expanded in association with the exponential relaxation theory. The simulation indicates that the relaxation is less at high densities than at low densities. Only a 2% output deterioration due to thermal relaxation was actually confirmed experimentally for about 105 seconds at 5 kFRPI, and there was almost no deterioration at 130 kFRPI. In contrast to longitudinal recording, less output reduction is observed for higher linear densities; this is well explained by the nature of the demagnetization field in perpendicular magnetic recording.

Side-writing of Merged Type Head for Perpendicular Double-layered Media

Availability of a standard thin film ring head merged to MR sensor was investigated for perpendicular double-layered media. It was found side-writing or erasure by the wide upper shield of the head took place under unsuitable writing condition which is harmful for high track density. Since a merged type thin film ring head acts like a single pole head with return path of upper shield, the side-writing by the upper shield appears at excess writing current. However the influence was found to be negligible by optimization of the recording MMF and head pole structure.