J. Z. Shi

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.

Grain size reduction in CoCrPt:SiO2 perpendicular recording media with oxide-based intermediate layers

CoCrPt–SiO2 perpendicular recording media containing an oxide-based intermediate layer have been studied in order to minimize the grain size in the recording layer. A RuCr alloy thin film deposited in an argon and oxygen reactive atmosphere was found to produce finer grains in the intermediate layer. When the recording layer was deposited on such an intermediate layer, the grain size of the recording layer was also observed to be smaller (about 6.4nm center-to-center distances). The results indicate that the introduction of RuCr-oxide-based intermediate layers is a possible approach to reduce the grain size in perpendicular recording media.

Advanced perpendicular recording media structure with a magnetic intermediate layer

CoCrPt–SiO2 perpendicular recording media containing a CoCr-based magnetic layer as an intermediate layer was studied. CoCr film deposited on a growth control layer such as Ta could grow with a hcp[0002] out-of-plane orientation, which could induce the desired perpendicular easy-axis orientation for the CoCrPt:SiO2 magnetic layer. It was observed that the growth of an intermediate layer based on Ru between the magnetic intermediate layer and the magnetic recording layer is crucial to reduce the noise. Recording performance of disks with a magnetic intermediate layer was comparable or better than that of conventional perpendicular media indicating the potential of the proposed structure.

Palladium-based intermediate layers for CoCrPt–SiO2 perpendicular recording media

CoCrPt–SiO2 perpendicular recording media containing Pd and Ru based intermediate layers have been studied. A Pd thin film with a face-centered-cubic (fcc)[111] orientation perpendicular to the film plane can induce a Ru hexagonal close packed (hcp) [0002] perpendicular orientation, which can subsequently induce a vertical Co hcp [0002] orientation for the perpendicular recording. It was observed that certain growth control layers (GCLs), such as Ta and CrTi, help in improving the growth of Pd significantly with a fcc[111] orientation perpendicular to the film plane. With the addition of such layers, the full width at half maximum (Δθ50) of the rocking curves was reduced from more than 11° to about 4°. Moreover, with a CrTi GCL, the intermediate layer could be as thin as 15nm. Recording performance of disks with CrTi GCL was better than that of disks with Ta GCL. The results indicate that the identification of a suitable GCL for Pd is a path to reduce the Δθ50 further.

Magnetic and Microstructural Properties of CoCrPt:Oxide Perpendicular Recording Media With Novel Intermediate Layers

Novel recording media layer structures for reducing the spacing between the soft magnetic underlayer and the writing head have been studied. In this paper, the kink in Kerr loops at zero fields is explained to arise from the depth-sensitive Kerr effect. Novel intermediate layer structures with two (RuCu) or three elements (RuCr:Oxide) are also proposed to reduce the grain size in the intermediate layer. This would, in turn, lead to a reduced grain size and grain size distribution in the CoCrPt:SiO2 recording layer

Experimental Study of Lubricant Depletion in Heat Assisted Magnetic Recording

Heat assisted magnetic recording (HAMR) is a promising choice to overcome the superparamagnetic limit in magnetic recording and further increase the areal recoding density of a hard disk drive. However, HAMR brings about serious lubricant depletion problems on the disk surface due to the high temperature in the heat assisted writing process. Experimental studies of the lubricant depletion under HAMR conditions are still very limited so far. It is essential to do experimental studies under real HAMR conditions or under equivalent conditions if a stand-alone laser is used to emulate the HAMR system. In this work, a self-developed HAMR tester is introduced. A method to control the repeatability of laser heating temperature is explained. Lubricant depletion, accumulation, loss, the percentage of accumulation to depletion, and the depth of depletion are determined quantitatively. The effects of laser power, total laser-on-time and laser-off-time in one laser heating and cooling cycle on lubricant depletion are studied experimentally with the HAMR tester. From the experimental studies, it is found that lubricant accumulation at the edge of the lubricant depletion track takes a considerable percentage of the lubricant depletion and the lower the laser heating temperature, the higher the percentage is. Furthermore, media cooling time plays a significant role in lubricant depletion for the media without a heat sink layer and on glass substrate.

Microstructure Control of

The FePt-C granular films for HAMR application have been developed by using the in-line sputter system. The microstructure development of the FePt-C granular films with different C contents was investigated. It was found that both the grain shape and the grain aspect ratio varied with increasing C content. The desired microstructure of FePt based granular film with well-isolated columnar grains was obtained for FePt granular film with 60 vol.% C doping. The mean grain size is nm and the grain aspect ratio is larger than 1. The developed FePt-C granular film with well-isolated FePt grains has the potential to be used as the recording media for HAMR application.

L1_{0}

The FePt-based granular films for heat-assisted magnetic recording (HAMR) application have been developed by using the in-line sputter system. The microstructure development of the FePt-based HAMR media as a function of different doping elements and film thicknesses was investigated. The microstructure of the FePtC-Ag granular film showed a nonuniform grain size distribution. FePt-C granular films with small and uniform grains were obtained at different film thicknesses. It was found that the grain size slightly increased with the increasing film thickness. The well-isolated FePt grains with main grain size of 6.4 nm ± 0.6 nm and 6.86 ± 0.8 nm were obtained for 6 and 10 nm FePt-C granular films, respectively. The developed FePt-C granular film with well-isolated FePt grains has the potential to be used as the recording media for HAMR application.

Ordered FePt Granular Film for HAMR Application

The role of substrate bias during the sputter deposition of various layers of double-layered CoCrPt−SiO2 perpendicular recording media has been investigated in order to understand the physical mechanisms behind the various effects observed. Perpendicular recording media with dual Ru intermediate layers were investigated using several magnetic and microstructural characterization techniques. It was observed that, in general, the application of a bias voltage during the deposition of the seedlayer (Ta) and the first intermediate layer (Ru) is helpful in reducing the c-axis dispersion of the recording layer. For the other layers, application of bias voltage leads to deterioration in the magnetic properties. It was also observed that the application of a bias voltage during the deposition of the first intermediate layer (especially Ru) may not enhance the preferred growth of Ru hexagonal-close-packed (00.2) planes parallel to the disk surface, as predicted before. However, the bias voltage on the Ru layer sti...

In-Line Sputter System Prepared

We report on the recording performance of discrete track patterned media fabricated by focused ion beam (FIB). We investigated performance over a small area by spinstand read/write testing. Discrete track patterned regions show smaller magnetic track width and better signal separation between adjacent tracks and therefore higher track density than that of nonpatterned continuous media as a result of reduced side fringe effect and edge noise. We found that, at a designed groove depth of 4-8 nm, the shallow FIB etched grooves already provide good isolation between adjacent tracks, indicating the superiority of ion beam induced modification of magnetic properties in film media over physical modification of disk surface topography. This has implications for discrete track recording and media fabrication.