Magnetic head surface

Stiction and Friction Properties of Seif-Assembled Monolayer on the Magnetic Head Surface... 

In this chapter, an introduction of experimental and theoretical studies on nanoparticles collision has been made, as nanoparticles impact on an ultra-smooth surface always occur in the ultra-smooth surface manufacturing. Then the development of CMP technology is introduced. And at last, the polishing of magnetic head surface is discussed. 

In addition, efforts have been made to explore the possibility of applying a monolayer as a lubricant to the surfaces of the magnetic head and disk, or both [32-35]. The results indicate ... 

In many cases of traditional tribology, friction and wear are regarded as the results of surface failure of bulk materials, the solid surface has severe wear loss under high load. Therefore, the mechanical properties of bulk material are important in traditional friction and wear. However, in microscale friction and wear, the applied load on the interactional surface is light and the contact area is also under millimeter or even micrometer scale, such as the slider of the magnetic head whose mass is less than 10 mg and the size is in micrometer scale. Under this situation, the physical and chemical properties of the interactional surface are more important than the mechanical properties of bulk material. Figure 1 shows the general differences between macro and micro scale friction and wear. 

This chapter introduces three kinds of surface organic modihcation hlms on a magnetic head that we have studied. These are polyfluoroalkylmethacrylate films, X-1P films, and self-assembled monolayers (SAMs). It also reviews the works of surface lube on a hard disk surface. In the last, the challenges on the development of a magnetic recording system are discussed. 

Fig. 4—The number of CF+ at different positions of the slider surface, (a) air bearing surface (ABS) of magnetic head, (b) CF numbers on different positions of ABS.

Partially fluorinated X-IP has been used for a number of years as an additive in the inert lubricant PFPE film on the surface of a magnetic hard disk to enhance start/stop durability of PFPE lubricants [29,30]. Recently it has been used as a vapor lubricated film on the surface of the disks [31 ]. In order to avoid the PFPE being catalyzed to decomposition by the slider material AI2O3 (refer to Section 3.4), XI -P was also examined as a protective film on the surface of the magnetic heads [25,32]. The results of CSS tests indicate that the thermal stability of the lubricant was greatly improved in the presence of X-1P, and the thickness of X-1P film on the slider surface has an important influence on HDD lubrication properties. 

The electron charge on the magnetic head was measured by a Guzik instrument. The parameter is chosen to judge the level of the surface electron charge of magnetic heads. When the value is close to 1, the electron charge on... 

Luo, J. B. and Yang, M. C., Surface Modification of Computer Magnetic Head, Sino-German Symposium on Micro Systems and Nano Technology, 7-9 Sept., Braunschweig, Germany, 2001. 

Luo et al. [1,153] used a slurry containing ultra-fine diamond (UFD) powders to polish the surface of HDD sliders. The powders are from 3 nm to 18 nm in diameter and 90 % around 5 nm. They are crystal and sphere-like [154]. The pH value of the slurry is kept in the range from 6.0 to 7.5 in order to avoid the corrosion of read-write heads, especially pole areas. A surface-active agent is added into the slurry to decrease the surface tension of the slurry to 22.5 Dyn/cm, and make it spread on the polish plate equably. An anti-electrostatic solvent is also added to the slurry to avoid the magnetoresistance (MR) head being destroyed by electrostatic discharge. The anion concentration of the slurry is strictly controlled in ppb level so as to avoid the erosion of magnetic heads as shown in Table 5. The concentration of UFDs in the slurry is 0.4 wt %. 

Figure 12 A magnetic head slider flying over a disk surface (slider located on the position 1.25 in. from the disk center rotating in 7600 rpm) compared with an aircraft flying in 560 mile/h over ground with a close physical spacing.

R. M. Crone, M. S. Jhon, B. Bhushan, and T. E. Karis, Modeling the flying characteristics of a rough magnetic head over a rough rigid-disk surface, J. Tribol. 113, 739-749 (1991). 

Shield design optimization for the CF-SPT head shows that critical dimensions such as shield gap length and shield height are expected to be in the order of a few tens of nanometers, as shown in Fig. 8.12. It is difficult to realize such a small shield structure using normal head fabrication techniques. However, the fabrication of a shielded CF-SPT head by a unique process has been demonstrated [17]. This process is as follows a soft magnetic material is deposited on the head surface followed by focused ion bead (FIB) milling to form the shield gap, as depicted in Fig. 8.13. Improvement in writing resolution was actually obtained for the fabricated shield head. 

This chapter provides experimental data for the magnetic head material removal rate and surface finish. These two parameters were considered as the important factors for the magnetic head manufacturer as it reflects the needs of the customers. In this step, where we super polish the magnetic heads, we are trying to obtain a direct relationship between slurry type and material removal rate. Other characteristics to be included are particle size, concentration, and amoimt more parameters will be included in future experiments. 

The first approach toward super polishing of magnetic heads attempts to provide qualitative and quantitative analysis of the resulting surfaces of the magnetic heads and the material removal rate of the process. Keeping other parameters as constant as possible and changing only the slurry t)q)e, we are able to determine the best choice to cover the customer needs in terms of production volume, economy, and surface quality. This fact will help the related industries to make appropriate suggestions to their customers needs. 

Image of a nonlapped magnetic head showing the topography of the surface. 

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