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Fe-Pt-Ag-SiO2 and Fe-Pt-Ag-C granular recording media with an L10 ordered structure were fabricated using an in-line sputtering system with full-surface alloy targets. To understand the degree of ordering, the x-ray diffraction intensity ratio of a superlattice peak to a fundamental peak was measured for various samples. Some samples showed large intensity ratios despite having low anisotropy energy. This can be explained by the simple theory that the relative intensity at a low diffraction angle increases for samples with weaker preferred orientation. That is, the intensity ratio is affected not only by the degree of ordering but also by the crystalline texture quality. The larger intensity ratio of Fe-Pt-Ag-C media than that of Fe-Pt-Ag-SiO2 media was interpreted as the degraded Fe-Pt(001) texture of Fe-Pt-Ag-C media. Thus, good Fe-Pt(001) texture needs to be achieved without deteriorating the well-isolated granular structure in Fe-Pt-Ag-C media.

A novel method of analyzing the switching field distribution (SFD) and magnetic correlation length of perpendicular magnetic recording media that uses major and minor magnetization loops is proposed. By applying the analysis to a series of capped perpendicular media, we found that a thick capping layer with a low saturation magnetization effectively reduced SFD without rapidly increasing the magnetic correlation length. Transmission electron microscope observation suggests that the SFD is narrowed by the increased uniformity of intergranular exchange coupling via the thick capping layer. Evaluations of recording characteristics demonstrated a close correlation between narrower SFDs and improved recording performance. Reducing exchange coupling dispersion is a clear solution for improving the performance of recording media.

The effect of the magnetic and structural properties on recording performance was investigated. Well grain-isolated media were obtained by adding boron and oxygen into the [Co/Pd]n multilayer and cooling the substrate. We found that the recorded bit size could be decreased by reducing the magnetic cluster size. Twenty-flve-nm bits were successfully recorded on the improved media with a magnetic cluster size of about 30 nm.

To evaluate properties of an initial growth layer for CoCrPt-SiO 2 perpendicular recording media, an initial growth layer has been investigated by micromagnetic simulation with initial layer model. It was found that with the initial growth layer, the in-plane magnetization Min shows a small jump at 0-field, leading to an additional peak around 0-field in 4 pi dMin/dH curve. The (additional) peak height increases with the increase in inter- lower subgrain exchange areal energy densities wi and thickness of the initial layer and also decreases in the anisotropy energy for the initial layer. Considering the change of the average anisotropy energy as a function of the thickness of recording layer, wi for a CoCrPt-SiO2 perpendicular recording medium with Ru/Ru-SiO2 intermediate layer is in the range from 0.5 to 0.6 erg/cm2 and roughly 30% smaller than those with a Ru intermediate layer

CoB/Pd multilayer films with a PtB/Pd/MgO intermediate layer were deposited on a soft-magnetic underlayer or on seeded substrates. A TEM analysis revealed that the multilayer films have a well-separated columnar structure just above an MgO layer. This structure may be initiated by the difference in the wetting nature of nonmetallic MgO and metallic Pd, and may be enhanced by the PtB layer. These boundaries were found to act in reducing the exchange coupling, resulting in an improvement in recording performance.

An intermediate layer for double-layer perpendicular media was investigated to weaken the intergranular exchange coupling of the CoCrPt alloy recording layer and to reduce the medium noise. When the intermediate layer was composed of an ultrathin Ta layer formed on an MgO film, the coercivity, thermal decay characteristics, and signal-to-noise ratio improved. The required average thickness of Ta layer was within 0.1 to 0.3 nm. The result suggests that the ultrathin Ta layer has an isolated island shape and plays the role of a template for the magnetically isolated grain growth of the recording layer.

In this study, we investigated the effects of PtB/Pd/MgO intermediate layers on the magnetic and recording characteristics of CoB/Pd multilayer media.

CoCr-alloy perpendicular magnetic recording media have been investigated, as the Cr segregated structure in the CoCr-alloy recording layer is suitable for obtaining low noise properties. Recently, the grain size of the recording layer is required to be very small for high-density recording, therefore the thermal stability of the recorded bit is becoming a critical issue. The magnetic anisotropy should be improved to keep the thermal stability of the recording layer which consists of small grains. The addition of the Pt element and a decrease of Cr content are required in the CoCr-alloy. This, however, results in higher medium noise due to increasing inter-granular exchange coupling. In this paper, the effects of Cr content on the magnetic and recording properties in post-annealed CoCrPt-alloy perpendicular media were investigated. The post-annealing treatment is expected to enhance Cr diffusion into the CoCrPt grain boundary from a nonmagnetic CoCr intermediate layer.

L10-ordered FePtAg-C granular media capped with an FePtAg-SiO2 layer were fabricated in order to obtain stable flyability performance on a spin-stand tester. The post-annealed FePtAg-SiO2 was more suitable for the cap layer than an FePt alloy without segregants, since it formed a continuous structure on the well-isolated FePtAg-C layer. By using the optimized post-annealed FePtAg-SiO2 capped medium, the surface roughness (Ra) was reduced to 0.45 nm, thereby enabling stable flying at a glide height of 6 nm.

FePtAg-SiO2 granular films were fabricated using an in-line sputtering system with a composite alloy target. Two heating methods were investigated in consideration of practical manufacturing processes. Structural analyses showed that the FePtAg-SiO2 film had better L10 ordered structure and clearer grain boundaries when deposited on the preheated substrate than when annealed after deposition. Adding Ag improved both the L10 ordering and the face centered tetragonal (001) texture. Torque magnetometry indicated that the FePtAg-SiO2 film had a uniaxial perpendicular anisotropy of 1.4 × 107 (erg/cc) at an ordering parameter S of 0.72.

We have investigated the role of the Ru underlayer for the segregated structure formation of CoCrPt-SiO2 granular thin film to improve the recording performance of CoCrPt-SiO2 perpendicular magnetic recording media. The coercivity of the granular film decreases with decreasing Ru layer thickness, which comes from the change in the segregated structure. Formation of an oxide grain boundary is needed to obtain higher coercivity. According to a morphology analysis, the Ru layer roughness is closely related to the coercivity. The results indicate that the oxide grain boundary formation of the granular layer is enhanced by the roughness of the Ru underlayer. The shapes of the Ru grains probably serve as a template in CoCrPt grain growth and oxide grain boundary formation. As one of the methods for enhancing the roughness of the Ru underlayer, an island shape growth on the low surface energy materials is applicable. The roughness of the Ru layer was increased using a Pd/MgO/Pd seed layer and high coercivity was successfully obtained even when the Ru layer thickness was 3 nm.

We developed a [Co∕Pt]n multilayer film for fabricating a perpendicular recording film with an ultrahigh coercivity (Hc). Adding boron into each Co layer and further introducing O2 during deposition yielded a high Hc of 1200kA∕m. Transmission electron microscopy and magnetic measurements suggested that the intergranular exchange coupling was reduced to the level of conventional CoCrPt-oxide granular films. The [CoB∕Pt]n+O multilayer film is applicable to a hard magnetic layer in exchange-coupled composite media as well as energy-assisted magnetic recording media.

A Ru–SiO2 intermediate layer was introduced between the Ru and recording layers to reduce the intermediate layer thickness of CoCrPt–SiO2 perpendicular recording media. A structural analysis revealed that the Ru–SiO2 intermediate layer enhanced the oxide segregation in the initial growth region of the recording layer. A micromagnetic simulation and magnetic property measurements indicated that the Ru–SiO2 intermediate layer reduced the intergranular exchange coupling in the initial growth region of the recording layer without magnetic anisotropy degradation. We reduced the intermediate layer thickness down to 9.1nm by using the Ru–SiO2 intermediate layer while maintaining the signal-to-noise ratio.