Yew Seng Kay

Influence of dual-Ru intermediate layers on magnetic properties and recording performance of CoCrPt–SiO2 perpendicular recording media

CoCrPt–SiO2 perpendicular recording media containing dual-Ru intermediate layers have been studied. The bottom Ru layer deposited under a higher mobility condition, i.e., low Ar gas pressure and bias on substrate, helps to achieve a good crystalline texture, and the top Ru layer under a lower mobility condition, i.e., high Ar gas pressure, promotes the formation of a columnar microstructure. Three kinds of grain boundaries have been observed. The nucleation field and the coercivity as a function of the thickness and dc bias of the bottom Ru layer have been investigated. Medium noise reduction has been observed for dual-Ru intermediate layer media (dual-Ru media) in comparison with that of single intermediate layer media (single-Ru media). This is mainly attributed to the optimization of the physical grain segregation.

Antiferromagnetically Coupled Patterned Media and Control of Switching Field Distribution

Switching Field distribution (SFD) is one of the critical issues for writing in bit patterned media (BPM) for high areal densities. It is believed that the magnetostatic interaction is one of the several factors that contribute to the SFD. With the antiferromagnetically coupled (AFC) structure, the magnetostatic interaction can be tailored to understand/reduce SFD. In this study, AFC patterned media is studied with emphasis placed on the effect of the top layer coercivity, which will determine the Mr and hence the magnetostatic interaction. For this study, nanodots with a size and space of 60 and 40 nm respectively were fabricated with electron beam lithography (EBL). Remanent hysteresis curves for the nanodot arrays were obtained by counting the number of reversed dots in magnetic force microscopy (MFM) images at remanent state. The narrowest SFD at a pressure of 1 Pa for top layer was observed possibly because of good crystaline texture and reduced magnetostatic interaction.

Microstructure and magnetic properties of CoCrPt–SiO2 perpendicular recording media with synthetic nucleation layers

Thermally stable, highly textured CoCrPt–SiO2 perpendicular magnetic recording media with ∼6nm size exchange decoupled grains and tight grain size distribution were prepared on synthetic nucleation layers. The media structure consisted of 14nm thick CoCrPt–SiO2 recording layer on one Ru intermediate layer. For these films, insertion of a synthetic nucleation layer directly under the recording layer was seen to reduce the grain sizes from 6.7to6.2nm and grain size distribution from 17% to 14%. Significant reduction in the intergranular exchange coupling interactions could be achieved while improving magnetic properties. The crystallographic texture of the recording layer remained strongly (00⋅2) oriented with the dispersion Δθ50 below 3.7°. Isothermal remanence magnetization and thermal stability behavior were studied. A model that describes the role of the synthetic nucleation layer in affecting the grain growth and magnetic properties of the recording layer is presented to understand these observations.

Influence of synthetic nucleation layers on the microstructure, magnetic properties, and recording performance of CoCrPt–SiO2 perpendicular recording media

The performance of CoCrPt–SiO2 perpendicular recording media, which incorporate synthetic nucleation layers for inducing grain size control, was evaluated with regard to the crystallographic, microstructural, magnetic, interfacial, and recording properties. The media structure consisted of a 14 nm thick CoCrPt–SiO2 recording layer sputtered on two stacked Ru intermediate layers. When a submonolayer thick synthetic nucleation layer was inserted between the two Ru intermediate layers, the grain size and grain size dispersion were significantly reduced in both the upper Ru layer and the recording layer. An average grain size of 5.8 nm with 20% dispersion was achieved for the recording layer. The crystallographic growth of the Co (00·2) perpendicular texture remained unaffected with the Δθ50 at ∼4.4°; the coercivity was ∼2800u2002Oe and the coercivity squareness was ∼0.6. The roughness of the interface between the synthetic nucleation layer and the upper Ru intermediate layer did not significantly change, and the...

Effect of RuCoCr-oxide intermediate layers on the growth, microstructure, and recording performance of CoCrPt–SiO2 perpendicular recording media

The crystallographic growth, magnetic properties, microstructure, and recording performance of CoCrPt–SiO2 perpendicular magnetic recording media on RuCoCr type of intermediate layers were systematically investigated. Excellent Cou2009(00•2) crystallographic texture with dispersion Δθ50 as low as 3.2° could be obtained on the RuCoCr as the grain isolation layer, whereas the Δθ50 on the pure Ru grain isolation layer was 3.9°. Upon injecting oxygen into the RuCoCr layer via reactive sputtering and at high sputter pressures, grain center-to-center distance as small as 5.9 nm with a distribution of about 13% was achieved. The Δθ50 deteriorated on the RuCoCr-oxide type of intermediate layers, however, it remained comparable to that on the pure Ru layers. Signal-to-noise ratio also increased on the RuCoCr-oxide grain isolation layers due to the decreased grain sizes. The effectiveness of the RuCoCr-oxide type of intermediate layers toward grain size reduction and in improving the performance of perpendicular magnet...

Novel planarizing scheme for patterned media

A novel planarization scheme, consisting of compression of a low glass transition temperature (Tg) and low viscosity poly(methyl methacrylate) (PMMA) polymer into grooves of patterned recording media using a surface with flat morphology, has been proposed and investigated. Si (100) surface was used as the smooth surface for pressing PMMA onto the patterned media. Patterned samples prepared with such a planarization method showed very smooth topography of roughness as small as 3 A (which is comparable to present hard disk media based on continuous film) by atomic force microscope. A magnetic sacrificial layer is proposed in addition as a solution to etching or polishing issues.

Antiferromagnetic iridium-manganese intermediate layers for perpendicular recording media (invited)

Current generation of cobalt-oxide-based perpendicular magnetic recording media uses single or dual ruthenium intermediate layers in order to grow crystallographically textured, and magnetically isolated granular media. In this work, the potential advantages of an antiferromagnetic iridium-manganese intermediate layer directly under the recording layer are highlighted. Owing to its close lattice matching with hexagonal cobalt, iridium-manganese which has the L12, or AuCu3-type crystal structure, can support the heteroepitaxial growth of the cobalt-based recording layer. In one of the media schemes described here, (111) textured iridium-manganese thin film was grown on 7.5 nm thick ruthenium layer. On the iridium-manganese as segregation layer, the Co-oxide-based magnetic recording layer showed perpendicular texture with Δθ50 below 4°, coercivity of over 4000 Oe alongside magnetic exchange decoupling, average grain sizes of 6 nm with distributions under 14%, and improved thermal stability. Measurements of ...

Low-Noise Crystalline Soft Underlayer for CoCrPt:SiO

In this paper, a crystalline soft underlayer with chemical formula (Fe₁₅Co₈₅)₉₄Cr₃Ta₃ for CoCrPt:SiO₂-based perpendicular media is studied. Three kinds of approaches are used to successfully reduce the noise from the soft underlayer. X-ray diffraction is used to study the effect of the preparation parameters on the orientations of the soft underlayer and the recording layer. The mechanism for the noise reduction is discussed