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This paper reports perpendicular magnetic recording (PMR) circumstances and the results based on the reference published by NEC. The PMR flexible disks using Co–Cr–Ta films were investigated. Pass wear durability of Co–Cr–Ta film strongly depends on the base film surface roughness and Young's modulus values of Co–Cr–Ta films. Pass wear durability, more than 10 million passes, was confirmed under a high temperature (60 °C) and a high humidity (80% RH) condition, as well as a low temperature (5 °C) condition. The read/write characteristics for double-layered PMR media were examined by using a combination of a single-pole-type (SPT) write head and a magnetoresistive (MR) read head, and a conventional merged ring type inductive (ID) write head/MR read head. By differential equalization of the reproduced voltage, the bit error rate less than 10 −6 at 3 Gb/in. 2 was obtained for the SPT/MR head combination. The antenna effect for PMR realization was analyzed using the merged ring type ID/MR head. In order to increase the magnetic circuit resistance from the ID head pole to the soft underlayer, we developed the sendust (FeAlSi) soft underlayer with low magnetic permeability. We confirmed that the recorded signal has better stability under the ID/MR head-loaded condition than the SPT head-loaded condition. These results show that there are the head and media solutions to realize PMR. We had confidence that we could use the basic structure of the commercial ID/MR head for the PMR head.

This paper describes a new type of power amplifier (PA) module with a predistortion function and can be applied to a N-CDMA (narrow-band CDMA system defined in IS-95B Standard) handset terminals. Distortion compensation technology to improve the efficiency of the PA is discussed, quantitatively. Various parameters to be considered in designing are investigated in detail. The predistortion technology proposed is based on the lookup-table method using the input and output signal envelopes and can operate independently from the baseband block. By omitting adaptative predistortion for amplitude/phase modulation and integrating the main controlling functions on a single CMOS integrated-circuit chip, the predistortion capability has been realized in a PA module. The PA module has a power-added efficiency (PAE) of 48% at an output power of 27.5 dBm. This PAE is very high in comparison with that of the conventional PA module for N-CDMA.

Track-edge noise in a written track and a partially dc-erased track was analyzed to clarify the edge noise properties of a side-erased band. It was found that the track-edge noise power and its noise components in a partially erased track are equal to those in a written track. The track-edge noise power in a side-erased band is the summation of the transition-edge noise power of old track, the overwritten track, and the bit-edge noise power.

The effects of recording heads on off-track noise characteristics were examined. It was found that an FeTaN head with a narrow gap and high Bs was very effective for decreasing both on-track noise and off-track noise, in com- parison with a NiFe head with a narrow gap or a merged- type NiFe head with a wide gap. It was also confirmed that, according to readback waveform analysis and MFM images observation, the fluctuations of the magnetic transition in track-edge regions for magnetic patterns recorded by the FeTaN head were much smaller than for those recorded by the merged-type NiFe head with a wide gap. It will become increasingly important to improve recording heads as their track width becomes narrower.

This paper describes the relation between pass-wear durability and medium tribological factors, including surface roughness, mechanical and chemical properties of CoCr and overcoat layers, lubrication and medium flexural rigidity. CoCr and overcoat layers were sputter deposited on various base films. Pass-wear durability was evaluated by using a single-sided 3.5″ flexible disk drive. CoCr wear strongly depends on the surface roughness and mechanical strength. The wear resistance is proportional to the tensile strenght of the CoCr films, in accordance with Archard's adhesive wear theory. The pass-wear durability is improved by surface treatments, including lubrication and overcoat application. A surface active agent is effective to increase the pass-wear durability, because lubricant affinity to the overcoat surface is improved. Furthermore, pass-wear durability is strongly influenced by medium flexural rigidity. By optimizing these tribological factors. sufficient pass-wear durability for practical use (more than 10 million passes) can be obtained.

The effect of remanent magnetic flux density (B/sub r/) and magnetic layer thickness (/spl delta/) on offtrack noise characteristics in Co-Cr-Ta alloy thin films is investigated. It has been found that decreasing the value of B/sub r/ is a more effective method of improving offtrack noise characteristics than decreasing the value of /spl delta/. Offtrack noise is shown to be due to the fluctuations in the amplitude of readback waveforms, fluctuations which are caused by fluctuations in magnetic transition amplitude. It was observed, using a magnetic force microscope, that lower B/sub r/ media had sharp boundaries at the track edge regions and the magnetization was more uniform, compared with those of higher B/sub r/ media.

Media noise characteristics of CoCrTa/FeSiAl perpendicular magnetic recording media were investigated to clarify the effects of underlayer characteristics such as crystalline orientation, surface roughness on the medium noise of double-layer media. A strong correlation was found between maintaining a smooth underlayer surface and attaining a low level of medium noise. Insertion of a Cr layer between the glass substrate and the FeSiAl underlayer and sputtering the underlayer at low Ar-gas pressure are effective in maintaining its surface smoothness. These measures reduce medium noise.

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.

Subjects for recording densities of 10Gbt/in2 - 30Gb/in2 are discussed, for longitudinal and perpendicular recording. Read-write specifications are estimated for their high recording densities. Reproducing outputs above 1mVpp/μm for magnetic heads are required. Correlation between magnetic media properties and recording densities are calculated for 10 - 30 Gb/in2 densities. Noise characteristics subjects and thermal instabilities are discussed for longitudinal recording media and perpendicular recording media.

The effect of the residual magnetic flux density (Br) on the media noise in Co-Cr-Ta alloy thin films has been investigated. Longitudinal media with higher Br and thinner magnetic layer have superior media noise to signal ratio compared to media with lower Br (below 2,000 G) and thicker magnetic layer under the constant Br δ, where δ is the magnetic layer thickness. It was revealed that media noise is proportional to fluctuations in the magnetic transition region according to analysis of the readback waveform. Furthermore, ferrite media exhibits an excellent possibility for use as a low noise media at high recording densities.

The recording noise of sputtered Co alloy media at high recording density was studied with readback waveform. High noise power of longitudinal recording media at high recording density was correlated to the fluctuation of magnetic transition region. In perpendicular recording media, in contrast, the fluctuation of magnetic transition region was small even at high recording density, which leads to low noise power.

This paper describes the relation between pass-wear durability and medium tribological factors, including surface roughness, mechanical and chemical properties of CoCr and overcoat layers, lubrication and medium flexural rigidity. CoCr and overcoat layers were sputter deposited on various base films. Pass-wear durability was evaluated by using a single-sided 3.5″ flexible disk drive. CoCr wear strongly depends on the surface roughness and mechanical strength. The wear resistance is proportional to the tensile strenght of the CoCr films, in accordance with Archard's adhesive wear theory. The pass-wear durability is improved by surface treatments, including lubrication and overcoat application. A surface active agent is effective to increase the pass-wear durability, because lubricant affinity to the overcoat surface is improved. Furthermore, pass-wear durability is strongly influenced by medium flexural rigidity. By optimizing these tribological factors. sufficient pass-wear durability for practical use (more than 10 million passes) can be obtained.

A new method of observing external bit fields emanating from recorded media is proposed. Fields are magnetically transcribed to a magnetic film located some distance from a recording surface and are observed by means of Lorentz microscopy. Some observed field patterns are shown, and the magnetic flux flows are analyzed.

Magnetic anisotropies were investigated for CoCr perpendicular magnetic films on grooved structure substrates (pitch length 2.1 mu m) prepared by CF/sub 4/-reactive-ion etching. Perpendicular magnetic anisotropy decreases in the region where groove depth GD >650 A. The reduction is due to the inclination of the crystal growth axis on the groove surface. In-plane magnetic anisotropy, K/sub u///, strongly depends on GD and saturation magnetization M/sub s/. In a region of large GD and large M/sub s/, Ku/sub /// is mainly due to shape anisotropy. In a region of small GD and small M/sub s/, K/sub u/// is caused by perpendicular magnetic anisotropy, in addition to shape and magnetorestrictive anisotropy. >

Bit shift characteristics are important parameters for perpendicular recording by ring heads on single-layer Co-Cr media. Bit shift dependences on media characteristics are studied experimentally. A simulation model of recorded magnetization transitions is presented to clarify the dependences under the following assumptions: 1) Media magnetization has a perpendicular component only and is constant through the thickness. 2) Media hysteresis is given by a rectangular loop, determined by H c and M s with no minor loop. It was found that bit shift differs only slightly with media thickness, and for a given bit shift, high recording density is obtained with low H c media.

Noise characteristics in Co‐Cr and Co‐Cr/Ni‐Fe perpendicular recording media were theoretically analyzed, based on an uncorrelated particle magnetization model. The analyzed results were compared with experimental results. Marked differences in noise spectra were found between single layer and double layer media, especially in the long wavelength region. The measured noise and signal spectra in a Co‐Cr/Ni‐Fe double layer medium were close to the numerically analyzed values for perpendicular magnetization, rather than for longitudinal magnetization. This indicates that the magnetization in the Co‐Cr layer is directed almost perpendicularly. Furthermore, the measured noise power decreased with increasing the medium perpendicular anisotropy, which is closely related to the medium crystal orientation. As a conclusion, noise from Co‐Cr perpendicular recording media is attributed to the medium grain magnetization direction dispersion, where the magnetizations are almost perpendicular to the medium surface.

The temperature effect on overwrite (OW) characteristics for magnetic recording, using various heads and media, has been examined. Overwrites depend linearly on the difference (T2−T1) between overwrite temperature T2 and previous recording temperature T1. Their gradients vary from −0.10 to 0.43 dB/deg, depending on head‐media combinations. The gradients are proportional to the difference (αBs−αHc), between temperature coefficient for head saturation magnetic flux density Bs and that for media coercivity Hc. Therefore, temperature dependence of overwrite is reduced by selecting a mead‐media combination with a small ‖αBs−αHc‖ value. This relation is explained by temperature variation in recording depth.

Magnetic properties and crystalline structures for sputtered FeTi films (0-40 at% Ti in composition), have been examined. The film structures were divided into three regions, bcc phase, transition region from bee to amorphous phase, and amorphous phase. In the transition region (15-18 at% Ti) from bcc to amorphous phase, FeTi films with perpendicular magnetic anisotropy were found. Saturation magnetization, magnetic anisotropy field, and perpendicular coercivity for a typical FeTi film (16.8 at% Ti) prepared in the transition region were 300 emu/cc, 2.7 kOe, and 710 Oe, respectively. Crystalline microstructures for FeTi films with perpendicular magnetic anisotropy are composed of amorphous phase and isolated pillar or pin-like crystalline grains (200-500 A) with bcc phase surrounded by the amorphous phase. Therefore, the origin of perpendicular magnetic anisotropy on FeTi films is mainly attributed to the grains shape anisotropy.