Thermally assisted magnetic recording (TAMR) is one of the novel technologies that are employed for achieving magnetic recording densities higher than 1 Tb/in 2 . With regard to this novel technology, it has been suggested that there exists a critical head-disk interface (HDI) issue associated with the use of ultrathin liquid lubricant films on the disk surface. This problem is attributed to the fact that these films are heated to high temperatures by using laser beams in order to reduce magnetic coercivity. In this study, a fundamental research on the lubricant depletion caused due to laser heating in TAMR systems was conducted. That is, the effect of lubricant film materials on lubricant depletion was investigated. In this experimental study, four types of lubricant film materials-Zdol2000, Zdol4000, Ztetraol2000, and A20H2000-were used, and the differences in the characteristics of lubricant depletion for each tested lubricant film were investigated. The effect of the molecular weight as well as the end group of the lubricant on the lubricant depletion was discussed and clarified by analyzing the obtained experimental results. In addition, it was found that the depletion characteristics of ultrathin liquid lubricant films could be explained by using experimental results obtained from the thermogravimetric analysis for each bulk lubricant material.Index Terms-Hard disk drives, laser heating, lubricant depletion, perfluoropolyether lubricant film, thermally assisted magnetic recording systems, thermogravimetric analysis (TGA).

A new magneto-optical (MO) disk. which consists of magnetic double layers. for super resolution readout was developed. We developed a new characteristic GdFeCo film as a readout layer whose magnetization direction changes from in-plane to perpendicular as a temperature rises. Using such a GdFeCo film combined with a DyFeCo recording film. higher linear density and track density than those of the conventional MO disks were achieved without an external magnetic field for readout and with a conventional optical head.

The 3D-MO (3-dimensional Magneto-Optical Recording) national project ended with a great success of achieving 100 Gb/in2 areal recording density with a new scheme of Double-MAMMOS1) (double recording layer MAMMOS, MAMMOS :magnetic amplifying magneto-optical recording system). A high performance write and read (W/R) tester equipped with a newly developed optical flying head (OFH), a low noise wide band photo detector IC (PDIC), and a high speed beam access system was developed. First surface (FS) MAMMOS disks for short wave length (405 nm) and high NA (0.9) optical system were also successfully developed and succeeded in a W/R test at 52 Gb/in2 areal density. Key words; magneto-optical recording, three dimensional recording, magnetic amplifying MO system (MAMMOS), optical flying head (OFH), high numerical aperture, short wave length (405 nm)

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