Bioactive glass, an osteoproductive material, has received considerable attention as a bone graft substitute in the treatment of bony defects. Bioactive CaO-SiO2-P2O5 glass was prepared using the sol-gel method, and mineralization behaviour in vitro was investigated by soaking it in simulated body fluid (SBF). Cellular cultivation in vitro, MTT (3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide) and Von Kossa assays were conducted to evaluate the osteoblast response to the bioactive glass. A calcium phosphate carbonate hydroxide (HCA) layer was formed on the bioactive glass after soaking for 3 days in SBF, which indicated that the mineralization on the surface of bioactive glass could progress spontaneously. The osteoblast response results demonstrated that bioactive glass had no cytotoxicity, and it might not be harmful to the morphology of the osteoblast. The growth and proliferation of the osteoblastic cell could not be inhibited. Nodule formation was also observed in conditioned medium containing dissolution bioactive glass and these nodules were shown to be mineralized by Von Kossa staining, which indicates that bioactive glass shows good biocompatibility.

In vitro degradation experiments of poly-L-lactic acid (PLLA) and bovine bone (BB) composites were carried out in a phosphate-buffered solution (PBS) at 37 degrees C with a pH of 7.4. The influence of BB content on pH value of PBS, water uptake, molecular weights, molecular weight distributions, weight losses, mechanical strengths, and morphologies of PLLA/BB was investigated with degradation times. The results indicated that the presence of the BB modified the degradation of the PLLA matrix. The degradation rate of PLLA in the PLLA/BB composite was slower than the degradation rate of the sole PLLA material. Furthermore, the degradation rate of the composites became slower with the increasing content of BB in PLLA/BB composites.

Continously and discontinuously exchange coupled capping layers were deposited onto a CoPtCrO recording layer. The magnetic and recording characteristics of CoPtCrO media with these various capping layers is reported.

The permeability of the magnetic soft underlayer (SUL) was systematically varied through SUL structure change, and its effect on wide area adjacent track erasure (ATE) and media overwrite (OW) was studied. Results suggest that ATE decreases with SUL permeability, and it involves only a finite thickness of the SUL. OW increases with SUL permeability as well as SUL thickness. In addition, ATE is less affected by magnetic spacing than OW. Antiparallel coupled SUL (APS) improves ATE. A double-APS structure with a permeability gradient is proposed to optimize OW and ATE performance.

We discuss a method of ac-demagnetizing an entire disk using permanent magnets and compare the demagnetized states of perpendicular media with different levels of intergranular exchange. The method consists of applying a large field perpendicular to the media recording layer anisotropy direction. This bulk ac-erasure technique provides a background noise that is lower than that which can be achieved by ac-erasing with a write head. Highly exchange-coupled media exhibit low dc noise but increased ac-erased background noise. Magnetic force microscopy data show increased magnetic roughness in the ac-erased state with exchange-coupling strength. For the media with least coupling the dc noise is similar to the ac noise.

The effect of magnetic "preconditioning" on the recording performance of perpendicular media is investigated. Furthermore, the dependence of the magnetic write width (MWW) of shielded-pole heads (SPH) on soft-underlayer (SUL) type and thickness (t/sub SUL/) and the recording performance of perpendicular media with thin SULs are examined. The MWW dependence on SUL structure is influenced by the pole-to-trailing shield spacing. For a wide-gap (/spl sim/80 nm) SPH, thick single-layer, SULs are preferred. For a narrow-gap (/spl sim/50 nm) SPH, MWW is less sensitive to the SUL type. For both narrow and wide-gap SPH and for media with an antiferromagnetically-coupled SUL, MWW is reduced for t/sub SUL/<100 nm. Comparable performance is achieved relative to media with t/sub SUL//spl sim/150 nm.

Antiferromagnetically coupled (AFC) media and conventional media (CM) were compared side to side over a wide range of orientation ratios (OR). For both AFC and CM, oriented media outperform isotropic media. AFC and CM show similar signal-to-noise ratios (SNR) throughout the entire range of OR. CM exhibit good SNR performance even at M/sub r/t<0.33 memu/cm/sup 2/ but with unacceptable thermal decay. When the coercivity is increased to match that of AFC at M/sub r/t<0.30 memu/cm/sup 2/, the SNR of the CM deteriorates and the thermal stability is still worse than the AFC. AFC offers some advantages in SNR roll-off in the isotropic media but not in the highly oriented media.

The effect of oxygen incorporation on the crystallographic, magnetic, and recording performance of perpendicular magnetic recording (PMR) oxide media was investigated. The media were prepared by dc-magnetron sputtering of CoCrPt-SiO/sub 2/ targets in an Ar/O/sub 2/ gas mixture. X-ray photoelectron spectroscopy (XPS) detected Cr-O peaks in the sputtered film, whereas no strong evidence of SiO/sub 2/ is seen. Moderate oxygen incorporation in the film (/spl sim/15 at%) promotes Cr-O formation in the grain boundary and results in a dramatic increase of coercivity H/sub c/ and signal-to-noise ratio (SNR). However, as the O/sub 2/ content is further increased, oxide incorporates into the core of the grains, resulting in decreased H/sub c/, magnetization and SNR.

A systematic investigation of the structural, magnetic, and recording properties of CoPtCrO media with different intergranular exchange coupling and anisotropy orientation dispersion is performed. Reduced exchange coupling between grains results in lower media transition jitter and nonlinear transition shift. By narrowing the Co anisotropy orientation dispersion, a substantial reduction of both transition and DC noise is achieved. Media with high squareness, coercivity, nucleation field, low exchange and narrow Co c-axis dispersion have been fabricated. Such media exhibit excellent recording performance and are promising for high-density perpendicular recording.

Compositionally graded magnetic multilayer (CGM) structures were investigated to improve media signal-to-noise ratio (SNR) as well as thermal stability. The medium structure consists of multiple magnetic layers that play an important role in determining the crystallographic texture as well as magnetic activation volume. Low medium noise is achieved while retaining high resolution, as the number of layers is increased. The CGM media offer a magnetic anisotropy gradient from the top to bottom layers, which enhances head writability at high frequencies without affecting thermal stability. Improved magnetic and recording properties such as high K-u V/kT, SNR, and overwrite are obtained with CGM media, suitable for high areal density recording.

A promising soft magnetic under layer (SUL) structure consisting of anti-parallel coupled soft layers (APS) is investigated to improve the performance of high-density perpendicular recording media. CoCrPt-O recording media with average grain diameter /spl sim/6 nm, coercivity of 5 kOe and nucleation field of -2 kOe is fabricated on both conventional SUL and APS. Wide-area adjacent track erasure (ATE) is observed for conventional SUL, which increases at lower interlayer spacing (t/sub IL/). APS structure enables the suppression of ATE even up to t/sub IL/=10 nm. Moreover, APS leads to reduced dc erase noise and improved signal to noise ratio particularly for SUL thicknesses <100 nm.

The surface morphology, thin film microstructure, and crystallography of sputtered longitudinal media were examined by atomic force and transmission electron microscopy. It was found that surface features along the texture lines in addition to the line density affect the measured orientation ratio. In addition, c-axis alignment along the texture line direction was established. These results point to magnetocrystalline anisotropy associated with the c axis as a major contributor to a high orientation ratio in these materials.

A superparamagnetic CoCrRu alloy is proposed for the intermediate layer (IL) between Ru/M2 in a typical antiferromagnetically coupled media structure M1/Ru/M2 (M2: recording layer). With the presence of the IL, the exchange coupling energy (Jex) initially increases from ∼0.09 to ∼0.10 erg/cm2 and asymptotes to ∼0.056 erg/cm2 when the IL thickness reaches 11 A. Due to its superparamagnetic nature, the CoCrRu IL does not introduce extra medium noise, in contrast to the ferromagnetic CoCrPtTa IL. The vibrating sample magnetometer thermal stability ratio (KV/kT) increases from 52 to 58 with a ∼7 Å CoCrRu IL, in agreement with the improved spin stand signal decay. X-ray diffraction scans indicate an improved epitaxial growth in the M2 layer when a CoCrRu IL is present.

A recording density of 130 Gb/in/sup 2/ was achieved using thermally stable conventional CoCrPtB longitudinal media. The high in-plane orientation ratio (OR) of the media resulted in an excellent recording performance due to a narrow switching field distribution as well as a high thermal stability caused by narrow energy barrier distribution. The low noise is attributed to the fully isolated fine grains with a narrow size distribution. A good in-plane c axis crystallographic texture was achieved by using an optimum multilayered structure of underlayer and magnetic layers. A detailed study of high OR media is reported by characterizing the magnetic, microstructural, and read/write properties.

We report on the recording performance and thermal stability of antiferromagnetically coupled (AFC) media with varying top and bottom layer thickness as compared with those of highly oriented conventional longitudinal recording media. AFC media offers the expected merit of low Mrt designs such as narrow pulse width (PW50), while maintaining good thermal stability. However, the magnetostatic field resulting from thicker total magnetic thickness in AFC media results in poor overwrite (OW) and a degradation in nonlinear transition shifts (NLTS). Thermal stability of AFC media is mainly determined by intrinsic coercivity of the top layer plus the AF exchange field and the magnetostatic field acting on the top layer through a Ru layer. Low noise conventional media with high orientation ratio (OR) can be produced with an acceptable thermal decay equivalent to AFC media at Mrt values above 0.25 memu/cm2.

Summary form only given. The complete presentation was not made available for publication as part of the conference proceedings.