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Effect of thickness ratio and interlayer exchange coupling on time-evolutional magnetization reversal process in stacked media with high coercivity was investigated by utilizing micromagnetic simulation. Regardless of the layer thickness ratio, for each stacked medium the magnetization reversal process is divided into three regions, namely the spin-flop rotation, the incoherent rotation and the coherent rotation along with increase of the interlayer exchange coupling constant Ainterlayer. In order to get the incoherent rotation region which is suitable for the recording media, it is required that the Ainterlayer is between about 1.3×10-7 and 2.2×10-7 erg/cm for the media with the layer thickness ratio of 1 : 3 and 3 : 1, and that one is between about 1.8×10-7 and 2.5×10-7 erg/cm for the media with the ratio near 1 : 1.

Influence of recording filed direction on transition noise of stacked media was investigated by using magnetic printing for recording and MFM images. Stray field fluctuation along the cross-track direction in the transition area and dispersion of the transition position of the recorded medium decreased as the applied field angle increased from the perpendicular direction. This shows that the transition noise decreases with increasing in-plane component of the recording filed. On the other hand, in the transition area domain size which corresponds to half of the period of the stray field fluctuation was fixed near 50 nm regardless of the applied field direction.

The relation between thickness and domain structure of Co80Pt20 perpendicular magnetic anisotropy films was investigated through experiments and micromagnetic simulation. The films with thickness over 10 nm exhibited clear maze domain structure, while for the films thinner than 10 nm the domain structure abruptly changed from maze domain to irregular and large domain as the thickness became thinner. The irregular domain had narrower domain wall width than maze domain.

Effect of interlayer exchange coupling on time­evolutional magnetization reversal process in ECC media with high coercivity was investigated by utilizing micromagnetic simulation. In the case of intermediate value of the interlayer exchange coupling, during the application of printing field, magnetization in the soft layer initially reverses and magnetization in the hard layer follows that of the soft layer. Furthermore, after removal of printing field, magnetization in the soft layer is reversed again according with that in the hard layer.

The effect of interlayer magnetostatic interaction on the domain structure of CoPt (3 nm)/Pt (δPt nm)/CoPt (10 nm) stacked films having perpendicular anisotropy is investigated. The domain structure of the demagnetized CoPt stacked films is observed using magnetic force microscope. The Co80Pt20 stacked films with Pt interlayer thickness δPt less than about 20 nm have the maze domain similar to that of the film with δPt of 0 nm. This is because the top and bottom layers are connected by the magnetostatic interaction and the magnetization distribution of both layers is integrated. The domain structure of the films with δPt around 25 nm is mixture of the maze and irregular domains. For the films with δPt over about 30 nm, because the interaction between the top and bottom layers decreases, the irregular domain which is observed in the 3 nm thick CoPt single layer film appears. In the region where the domain structure changes from the maze domain to the irregular one, domain size steeply increases with increase of δPt. [ABSTRACT FROM AUTHOR]

Domain structure of stacked media demagnetized with perpendicular or in-plane demagnetization field is investigated using MFM. For a demagnetized medium (sample A), the domain size is approximately 50nm regardless of demagnetization field direction, while the contrast of the MFM image for the in-plane demagnetized sample is lower than that for the perpendicularly demagnetized sample. The domain of sample B where the cap layer was etched from the sample A is similar to that of the sample A in case of perpendicular demagnetization, which shows the domains of the cap and granular layers are integrated. Meanwhile, in case of in-plane demagnetization, the domain of the sample B is hardly observed, which suggests the domains of the cap and granular layers of the sample A are not integrated, and it is probable that the sub-domain structure is formed in the cap layer. The domain of sample C demagnetized in-plane after etching the cap layer from the stacked medium is hardly observed like the sample B, which shows that the domain of the granular layer of the sample A is not affected by the cap layer. [ABSTRACT FROM AUTHOR]

Servo pattern printing (SPP) is recognized as a candidate for the future high resolution and high throughput servo track writing method. In terms of the application to perpendicular magnetic recording (PMR) media, there are two methods of SPP, 'edge printing (EP)' and 'bit printing (BP),' which use horizontal and vertical external field during printing process, respectively. Comparing between EP and BP, EP has higher potential for the PMR application, because of the properties of a dc-free signal, a higher signal-to-noise ratio (SNR) and smaller repeatable run out (RRO) from 8th to 19th order than a conventional head writing method. In the simulation, the less write-fringe of the recorded bits was confirmed as the benefits of EP. The most recent experiment demonstrated 55-nm bit length (BL) with adequate read back signal and EP is considered to have adaptability to the areal density beyond 48 Gbits/[cm.sup.2] (300 Gbpsi). Index Terms--Hard disk drive, magnetic printing, patterned master, perpendicular magnetic recording media, repeatable run out (RRO), servo track writing.

The magnetization patterns of slave media duplicated by using patterned master media are examined. The duplicated magnetization reverses at transitions and changes between transitions for bit lengths of more than several mu m whereas the magnetization reverses at transitions and is found to be uniform between transitions for bit lengths less than several mu m.

A study was conducted to analyze the angular dependence of the coercivity for vacuum evaporated Co-O films with oblique anisotropy in an in-plane and in a normal plane to examine the magnetization reversal mechanism. Experimental results indicated that the magnetization reversal mechanism at the films is the incoherent rotation. Moreover, the interaction among the grains is different in both planes.

In this study, the effect of the magnetostatic interaction in the bilayer nanowires with perpendicular magnetic anisotropy and low saturation magnetization on the current-induced domain wall motion has been investigated by using micromagnetic calculation. The bilayer nanowire, which consists of continuous layer (CL) and granular layer (GL), is used, and the saturation magnetization in each layer is varied. As a result, domain walls in CL and GL move together as the domain wall structure and the velocities vary. The domain wall motion in bilayer nanowires can be divided into two modes. In one mode, the velocity of domain wall varies when the domain wall structure switches between Bloch and Néel walls. In the other mode, the velocity of domain wall varies when the domain wall structure switches between 90° and 270° of Néel walls. Moreover, the critical current velocity, which corresponds to the spin transfer velocity in the bilayer nanowires, increases with increasing saturation magnetization of the continuous layer and the granular layer. This is because the total energy difference which is the energy difference between two extreme values in total energy as a function of magnetization angle at wall and is proportional to the hard-axis anisotropy energy increases with increasing saturation magnetization of the continuous layer and the granular layer. [ABSTRACT FROM AUTHOR]

The influence of the magnetic films formed at the dent parts of the master media on the duplication performance is discussed. The duplication performance for the lithographically patterned master media with and without magnetic films at the dent parts is presented.

The change in magnetization at the transition and the transition noise of the stacked media recorded with a single pole head without a trailing shield (SPH) and a head with a trailing shield (TSH) were investigated by using micromagnetic simulation. As a result, it was found that the linearity of the transition was higher and the transition noise was lower for the medium recorded with the TSH as compared with the medium recorded with the SPH. This is because stronger in-plane recording field of the TSH caused many small reversed domains. The relation between the magnetization distribution of the transition area and the direction of the recording head field reflected the relation between the domain structure of demagnetized media and the direction of the demagnetizing field. [ABSTRACT FROM AUTHOR]

We observed the readback signal from a floppy disk (FD) media prepared by a novel magnetic contact duplicated method. The signal amplitude, PW50, and CNR were nearly same as that using the traditional method. It was confirmed that this technique has the high potential to write servo signals in high Hc media. Index Terms--Magnetic contact duplication, servo-writing, floppy disk.

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 one. 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. Index Terms--Magnetic contact duplication, servo-writing, hard disk, floppy disk.