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The magnetic anisotropy of CoPtCr-SiO2 perpendicular recording media, including higher energy terms, was studied as a function of film composition and seed layer materials. All series of CoPtCr films with various Cr content, deposited on Ru seed layers, show maximum values of total anisotropy Ku at 25-30 at%Pt. The maximum value for CoPt(Cr = 0) films reaches ∼ 15 × 106 erg/cm³. The addition of SiO2 to the CoPtCr films reduces the grain Ku, however the grain Ku maintains a large value of 8 × 106 erg/cm³ even when 10 at% SiO2 is added to (Co90Cr10)80Pt20, for instance, which indicates the high-potential thermal stability. Theoretical calculations for media designs of 400 Gbits/in² revealed that the ratio of the high-energy anisotropy term Ku2 to Ku1 (Ku = Ku1 + Ku2) is required to be 0.2-0.35 to enhance the energy barrier for the remanent state, without a notable change in switching field. The films deposited on Ru seed layers were found to show negligibly small Ku2 values, however, the values of Ku1 and Ku2 vary significantly with the seed layer material used. Ku1 decreases almost linearly as the Ku2 value increases. It is concluded that CoPtCr films have a sufficient potential in the values of Ku1 and Ku2 for high-density perpendicular media. [ABSTRACT FROM AUTHOR]

An implicit locally 1-D body-of-revolution finite-difference time-domain method is efficiently implemented using a fundamental scheme. The formulation with dispersion control parameters is performed in convenient matrix-operator-free forms in the right-hand sides of resultant basic equations. The Higdon absorbing boundary condition is also incorporated. Modification to the calculation procedure reduces memory requirements for auxiliary variables, compared with the original fundamental scheme. The usefulness is discussed through the analysis of a fiber Bragg grating. [ABSTRACT FROM PUBLISHER]

The first and second order energy terms of uniaxial magnetic anisotropy, Ku1 and Ku2, of CoPtCr-SiO2 perpendicular recording media were studied as a function of film composition and film structure. Moreover, the fabrication of CoPtCr-SiO2 media having ade- quate values of Ku1u1 and Ku2 for high recording density was preliminarily studied. An analysis of CoPtCr films with various kinds of seed layer materials revealed that the values of Ku1 and Ku2 varied significantly with the seed layer material used, probably due to epitaxial growth of CoPtCr on the seed layers. Ku3 increased, accompanied by a reduction in Ku1 as the c/a ratio of the hcp-CoPtCr lattice increased. Moreover, experimental results suggest that a high stacking-fault density enhances the Ku2 values, especially in the high Pt content region. The addition of SiO2 reduces the total anisotropy, Ku1 + Ku2, but no significant change in the ratio of Ku2/Ku1 was observed. The fabrication of CoPtCr-SiO2 media with adequate values of Ku1 and Ku2 was successfully demonstrated, although more intensive efforts to enhance grain isolation are required to confirm the advantages conferred by the Ku2 term. [ABSTRACT FROM AUTHOR]

Hard/soft-stacked perpendicular recording media were proposed in order to imp rove recording writability without notable changes in thermal stability and noise performance. A preliminary study on stacked media consisting of a 10-nm magnetically hard CoPtCr-SiO2 layer underneath a soft NiFe-SiO2 layer (0-4 nm) was performed. Transmission electron microscope images revealed that NiFe/CoPtCr stacked grains were well isolated by SiO2 at grain boundaries, similar to the isolation of single layer CoPtCr-SiO2 media. No change was observed in the slope of the hysteresis loop on stacking the NiFe-SiO2 layer, suggesting there was no significant change in intergranular magnetic coupling. The switching field decreased by 2 kOe as the NiFe-SiO2 layer thickness increased from 0 to 3 nm, without a notable reduction in the stabilizing thermal energy barrier. Moreover, the angular dependence of remanence coercivity indicates that magnetization reversal occurs by coherent rotation in (CoPtCr/NiFe)-SiO2 stacked media as predicted theoretically, and no significant difference in switching mechanism from single layer CoPtCr-SiO2 media was observed. We successfully demonstrated that the hard/soft-stacked media show a better recording writability with no notable change in signal-to-media-noise ratio or thermal stability. [ABSTRACT FROM AUTHOR]

Magnetic properties and recording performance of thin CoPtCr-SiO2 media were examined in relation to thermal stability. Magnetic anisotropy Ku of {(Co90Cr10)80Pt20}89-(SiO2)11 media maintains a constant value of around 5.5 × 106 erg/cm³, even at film thickness of 4 nm. This Ku value corresponds to the anisotropy energy of the grains Kuq calculated by taking account of the volume fraction of about 8 × 106 erg/cm³, indicating a high potential to resist thermal agitation. The high Ku derives a high remanence corcivity Hr of ∼ 4 kOe, even at film thickness of 8 mit, resulting in a loop squareness of nearly 1. The ratio of magnetic anisotropy energy to thermal energy Ku Vact/kT maintained a value of more than 70, even at this thickness. The media noise at low recording density increases with decreasing film thickness below 8 nm, probably due to the thermal agitation. The recording resolution D50 showed a broad maximum of ∼420 kFCI at around this thickness. The reduction in film thickness improves recording resolution; however, it is likely that the large thermal agitation in the thin-film region degrades the recording resolution, resulting in an optimum thickness to show the highest recording resolution. [ABSTRACT FROM AUTHOR]

Optimization of the SiO2 content for high-density recording was discussed for {(Co90 Cr10)80Pt20}100-z-{SiO2}z perpendicular recording media. The grain size Dgrain decreases significantly from 8.8 to 5.4 nm as the SiO2 content Z increases from 0 to 14.4; however, no significant difference in c-axis orientation was observed. Magnetocrsytalline anisotropy of grains maintains a large value of nearly 8 × 106 erg/cm³, even at 10 at % SiO2 addition, indicating a high potential of perpendicular anisotropy Ku to resist thermal agitation of magnetization. The coercivity Hc increases significantly as the SiO2 increases, which is coincident with the reduction of the slope of magnetization curve α = 4π(dM/dH) due to the enhancement of grain isolation. The Hc shows a maximum at around 11 at % SiO2 (nearly 30 vol % SiO2). A further increase of SiO2 reduces the value of Hc significantly, although the a maintains a constant value of nearly 2, due to thermal agitation of magnetization. The media noise reduces significantly as the SiO2 increases; however, the addition of SiO2 beyond about 13 at % leads to a slight increases in media noise probably due to a significant increase of thermal agitation. The recording resolution D50 shows a broad maximum of ∼ 420 kFCI at around 11 at % SiO2, Suggesting that the D50 is related to the media noise performance Experimental results indicate that there is a tradeoff to be made between the thermal stability and media noise performance as a function of SiO2 composition. [ABSTRACT FROM AUTHOR]

The perpendicular magnetic anisotropy Ku of CoPtCr films deposited on Ru seed layers is discussed as a function of film composition. Moreover, the change in Ku by the addition of Sio2 is examined in light of thermal stability of CoPtCr-SiO2 media. The Ku of Co-10 at % Cr shows a high value of ∼ 5 × 106 erg/cm³, which is much higher than that reported by Bolzoni et al. The addition of Pt to the Co-10 at % Cr film results in a further enhancement of Ku A maximum Ku of nearly 10 × 106 erg/cm³ is observed at 25 ∼ 30 at % Pt. All series of films with various Cr contents show maximum values of Ku at 25 ∼ 30 at % Pt. The maximum value for Copt (Cr = 0) films reaches ∼ 15 × 106 erg/cm³. The value of magnetocrystalline anisotropy of grains Kug, calculated by talking account of the volume fraction of CoPtCr grains, decreases as the 5102 content increases. -However, the Kug maintains a large value of more than 7 × 106 erg/cm³, even at 10 at % SiO2 in addition to (Co90 Cr10)80Pt20, which indicates a high potential of CoPtCr-SiO2 media to resist thermal agitation of magnetization. [ABSTRACT FROM AUTHOR]

The magnetic cluster size D[subcluster] of perpendicular recording media, which is a main factor in media noise, is discussed in terms of demagnetizing field of magnetic clusters, remanence coercivity, and magnetization switching. It was shown that the values of remanence coercivity obtained by subtracting thermal agitation effect H[sub0] are ∼70% of those calculated using the Stoner-Wohlfarth model taking account of the c-axis distribution, H[supS-W][subr], even in CoPtCr-SiO[sub2] media with well segregated grains. Demagnetizing field of magnetic cluster H[subd] is calculated as a function of the ratio of D[subcluster] to film thickness, δ. An intrinsic remanence coercivity H[supint][sub0] was obtained by compensating the H[sub0] value by the H[subd](H[supint][sub0] = H[sub0] + H[subd]). The H[supint][sub0] values are very close to those of H[supS-W][subr] especially in media with well-segregated grains. This result means that the magnetization reversal of these media is mainly determined by coherent rotation of magnetization; however, the demagnetizing field of magnetic cluster, besides thermal agitation effect, reduces the value of H[sub0]. [ABSTRACT FROM AUTHOR]

Presents a study which examined the microstructure and magnetic properties of cobalt platinum chromium-silicon oxide perpendicular magnetic recording media. Background information on cobalt chromite-based perpendicular media; Experimental procedure; Results and discussion.