Slave Media Research Articles

Effect of Spacing between Master and Slave Media on Printing Characteristics

The effect of spacing between master and slave media on printing characteristics was investigated in this study by using micromagnetic simulation. The results indicated that the printing characteristics were improved as the spacing decreased. At the optimal printing magnetic field, the effect of the spacing for checker pattern was larger than that for L/S pattern. Decreased in the spacing expanded the tolerance region in which superior printing characteristics were obtained. Moreover, decreased in the spacing also expanded the overlap region between tolerance regions for two patterns.

Micromagnetic study of magnetic printing onto various slave media

In this paper, the micromagnetic analysis of magnetic printing onto various slave media, such as the coupled granular-continuous media (CGC) and exchange coupled composite media (ECC) was carried out. In the single-layered granular medium, the magnetization patterns are printed on the slave medium corresponding to the master patterns, but defects appear in the center of the magnetization pattern in this case. On the other hand, in the CGC and ECC media, there is no defect in the center of the magnetization patterns due to the effect of a capping layer. The bit squareness in ECC medium is superior to those of the other media. It is clarified that the magnetic printing can be applied onto various media.

Perpendicular Anisotropy Master Medium in Magnetic Printing for Writing High-Density Servo Signal

A perpendicular anisotropy master medium (PAMM) has been proposed for magnetic printing, and it is expected to improve the printing characteristics of the servo signal. In this study, we experimentally performed magnetic printing by using the PAMM, which is composed of CoPt magnetic film, with perpendicular magnetic anisotropy and large saturation magnetization. It is clarified that the optimum printing field for PAMM is 3.5 kOe, which is 0.5 kOe lower than that of conventional master medium, and that the output signal from the slave medium printed by PAMM is about twice larger than that of the conventional master medium. Furthermore, the printing characteristics for PAMM can be further improved with thicker magnetic film.

Influence of the Master Pattern Angle on Perpendicular Magnetic Contact Printing Characteristics

The influence of the inclination angle of the master pattern on the edge printing characteristics for writing phase servo patterns on perpendicular magnetic recording media was investigated. Even if the master pattern angle is 40 degrees, the printing characteristics are only 10 percent lower than when the angle is 0 degrees. The influence of the inclination angle of the master pattern on the printing characteristics is also small when the bit length is changed. The contribution of the in-plane component of the recording field to magnetization reversal is large in edge printing. Although the perpendicular component of the recording field decreases markedly as the inclination angle of the master pattern increases, edge printing can be used for writing phase servo patterns on slave media.

Analysis of waveform from perpendicular magnetic printed media

Edge printing is one of the perpendicular magnetic printing methods for writing servo signals with high speed, high accuracy and low cost. Sub-peaks of waveform from edge printed media are concerned as the sub-peaks can cause errors during the read-back process. In this study, in order to reduce sub-peaks, the influence of printing field, bit length and patterned magnetic layer thickness of master medium on sub-peaks is investigated by using a metal-evaporated (ME) tape as a slave medium. The results show that sub-peak to main peak ratio decreases with stronger printing field, smaller bit length and thicker patterned magnetic layer of master media.

垂直磁気転写特性のマスターパターン傾斜角依存性の拡大モデルによる解析

The influence of the inclination angle of the master pattern on the duplication characteristics during the formation of a phase servo pattern on perpendicular magnetic recording media by edge printing was investigated by using an enlarged model. The perpendicular components of both the recording field and the magnetization of the duplicated slave medium decreases as the inclination angle of the master pattern increases. The influence of the inclination angle of the master pattern on the magnetization is small in comparison with the influence on the recording field, and even for an angle of 40 degrees, edge printing on slave media is possible.

Influence of Spacing between Master and Slave Media on Magnetic Duplication Characteristics for Perpendicular Recording Media

There are two methods of writing servo signals with high speed in a perpendicular magnetic recording medium by magnetic duplication: bit printing (BP) and edge printing (EP). In this study, the influence of spacing between master and slave media on duplication characteristics in both BP and EP has been investigated by the three-dimensional finite-element method. The results show that the duplication characteristic in each method is deteriorated with a large spacing. Also, the influence of a small spacing is stronger in BP than in EP.

蒸着テープを用いた垂直磁気転写解析

The duplication characteristics of perpendicular magnetic media were analyzed by using metal evaporated (ME) tape as a slave medium. In the case of bit printing (BP), the best duplication characteristic was obtained at a duplication field of 4 kOe, about 2 times higher than the coercivity of the ME tape. On the other hand, in the case of edge printing (EP), duplication characteristics were saturated when the duplication field was more than 3kOe. When the duplication field was strengthened, in the case of BP, the peak position shifted towards the outside of the magnetic layer of the master, whereas, in EP, the peak position shifted towards the center of the magnetic layer. The calculated MFM output waveform obtained by using computer simulation almost coincided with the experimental result, and the cause of the sub-peak could thus be explained. It was concluded that EP has better duplication characteristics than BP.

Influence of Soft-under-layer in Perpendicular Recording Media on Recording field of Magnetic Duplication

The magnetic field distributions around slave media with and without SUL were calculated by using the finite element method to estimate what influence a soft-under-layer (SUL) in a double-layered perpendicular medium had on magnetic duplication characteristics. As a result, we found the SUL enhanced duplication characteristics for any bit length and track width. The SUL in bit printing influences the duplication characteristics more than that in edge printing. The influence of SUL on duplication characteristics in bit printing increases as the strength of the duplication field increases. However, in edge printing, there is a duplication field that maximizes the influence of SUL on duplication characteristics. Moreover, the influence of SUL on duplication characteristics decreases with both bit and edge printing as bit the length of the magnetic pattern decreases, and also decreases as the track width decreases. These dependencies can be explained by taking the demagnetization coefficient of SUL and the total amount of magnetic charge appearing in SUL and magnetic patterns into account.

垂直磁気記録媒体への磁気転写シミュレーション

The characteristics of magnetic contact duplication for perpendicular magnetic recording media are investigated by using the three-dimensional finite element method. In order to magnetically duplicate a servo signal on perpendicular recording media, there are two methods of applying a duplication magnetic field. One is method to apply a magnetic field in a direction perpendicular to the disk plane (perpendicular field application, PFA), and the other is to apply a field in the disk plane (in-plane field application, IFA). In PFA, the dependence of the duplication performance on the field strength has an optimum value which is around the coercivity of the slave medium. In IFA, the duplication performance is improved by increasing the duplication field up to a certain field strength beyond which the strength the performance is saturated. Duplication characteristics of the slave media change a little even though the track width decreases in the case of PFA, while it decreases with decreasing track width in the case of IFA. The results of simulation show that IFA is more advantageous than PFA for duplication of perpendicular magnetic recording media.

スレーブ媒体磁化困難軸方向に対するマスターパターンの傾きが磁気転写特性に及ぼす影響

Magnetic contact duplication is proposed as a method for forming phase servo patterns on hard disks. In a phase servo pattern, the magnetic field used for duplication is applied diagonally across the master pattern. This work clarifies the influence of the master pattern angle θ against hard magnetization direction of the slave medium on the magnetic duplication characteristics. In the case where θ= 30°, the output signal voltage decreases and the half-value width of the signal becomes broad compared with that for θ= 0°; that is, the magnetic duplication characteristics deteriorate as θ increases. Even if the duplication field is made strong for large θ, the magnetic duplication characteristics are not improved.

磁気転写特性に及ぼすマスター・スレーブ間スペーシングの影響

In the patterned master magnetic contact duplication technique, the spacing between master and slave media seriously affects the duplication characteristics. When a slave medium with coercive squareness S* of 0.43 was duplicated by using a master medium with a pattern width L of 2.5 μm and a magnetic layer thickness of 1 μm, it was found from experiments and simulation that the spacing loss factor K is about 30 dB. The reason for this small value is that the recording demagnetization in the duplication process is very weak. It is shown by simulation that a higher S* value in slave media is advantageous for the patterned master magnetic contact duplication.

Influence of master medium structure on magnetic contact duplication performance

In the magnetic contact duplication technique using lithographically patterned master media, when the master media have magnetic films not only in the protrusion parts but in the dent parts, the depth of the dent parts affects the duplication performance. For the master media with a pattern width L of 2.5 μm, both experimental and simulation results show that even though there are magnetic films at the dent parts, if the depth of the dent d is 0.5 μm, the degree of magnetization reversal at transitions of duplicated slave media is much the same as that for the master media without magnetic films at the dent parts. It is inferred from simulations that for the master media with L of 0.1 and 0.4 μm, if d is 0.1 and 0.2 μm, respectively, magnetic films at the dent parts have no influence on the duplication performance.

磁気転写による記録状態のシミュレーション

A finite element 2D simulation of recorded magnetization on a slave medium with patterned thin films on a master medium was performed by solving the Poisson equation for the magnetic printing system. As a result, the following conclusions were drawn: (1) The printing field decreases drastically in the central region of two magnetic films as compared with that at the film edges. (2) When the printing field is weak, the magnetization in the central region cannot be switched under the printing field, and the output voltage waveform is severely distorted. (3) When the printing field is too strong, the peak of the output voltage waveform shifts in the film edge direction, although the magnetization can be switched completely. (4) The optimum printing field depends strongly on the distance between the films.

パターニングされたマスター媒体を用いた磁気転写

A magnetic contact duplication technique using a lithographically patterned master medium was investigated in order to write a servo signal on hard disks and floppy disks at high speed and low cost. In this technique, the coercivity of the master medium is low, and a dc magnetic field is applied to a slave medium in contact with the master medium. Experimental and computer simulation results show that the degree of magnetic duplication becomes better and then saturates as the magnetic layer thickness of the master becomes thicker. Magnetic duplication performance improves with the increase of Ms of the master.

A novel magnetic contact duplication technique for servo-writing on magnetic disks

A novel magnetic contact duplication technique is proposed in order to write a servo signal on hard disks and floppy disks at a high speed and a low cost. In this technique a magnetic layer of a master disk is lithographically patterned in accordance with a servo signal, having low coercivity, and dc magnetic field is applied to a slave disk contacted with the master one. A computer simulation using finite element method shows that the pattern of the master disk can be duplicated on a slave. The possibility of duplication by using this technique is confirmed from experimental results in which a Bitter pattern of a duplicated slave medium is clearly observed.

Magnetic printing of data from soft magnetic patterns

A technique of magnetic printing utilizing a master with soft magnetic pattern has been developed to answer the need for printing data on magnetic media in large quantities. In such a master, sections of highly permeable magnetic materials are deposited according to the data pattern to be printed onto the slave media. The soft magnetic master is then placed in close contact to the slave media and a magnetic field is applied to induce a field sufficient to record on the slave media, from the discontinuities in the master. The soft magnetic master and printing station are designed with the help of a computer simulation of the process. Optimization of the printing method was carried out empirically. It is shown that this method enables signals from printed media to be comparable to those from directly recorded data. The method has an advantage, in that the soft magnetic master can be used repetitively on media with a wide range of coercivity without damaging the magnetic properties of the master.

The magnetic transfer process

The transfer of information from a magnetic surface master to a magnetic surface slave when they are brought in to intimate contact in the presence of an external magnetic field is discussed. The only effective component of the transfer field was found to be the component in the plane of transfer and collinear with the recorded magnetization. Steady fields were found to be only slightly inferior in transfer efficiency to alternating fields, and the optimum amplitude for both is equal to the remanence coercivity of the slave medium. The basic mechanism of the magnetic transfer process is shown to be the establishment of a relatively large susceptibility in the slave by the transfer field, thus rendering it a good receptor of the flux emanating from the magnetization gradients in the master. Under certain conditions it was found that digital information could be transferred from a high resolution master onto thick or low coercivity media with a significant improvement in resolution over what could be achieved by direct recording with conventional transducers on the same media.