Magnetic heads

The INTROS MDK-21 consists of an electronic unit and two or three magnetic heads (Fig. 3). Table 1 shows the specification of the magnetic heads. 

There are three changable sensor units for the MH-24/64 magnetic head as like as for MH-24. The units must be changed when rope diameter changes more than two times. The sensor units of the MH-40 and MH-54 are unchangable. So the MH-40 and MH-64 heads are more releable having no connectors for this. 

The INTROS Flaw Detector is able to inspect ropes moving through the magnetic head at speed 0...2 m/s. Limit of sensitivity to wire brake is 1% of the rope meatallic cross-section area, the LMA measure accuracy is not less than 2%. 

Calibration procedure bases on rope specimens and corresponds to the Standard Pratice ASTM 1574. It takes a piece of the rope under test having a nominal metallic cross-section area (LMA=0) to set zero point of the instrument. Rope section with the LMA value known is used to set the second point of LMA calibration charactiristics. It is possible to use the air point calibration when there is no rope in a magnetic head (LMA=100%). 

Another important application area is the non-destructive defectoscopy of electronic components. Fig.2a shows an X-ray shadow image of a SMC LED. The 3-dimensional displacement of internal parts can only be visualized non-destructively in the tomographic reconstmction. Reconstructed cross sections through this LED are shown in Fig.2b. In the same way most electronic components in plastic and thin metal cases can be visualized. Even small electronic assemblies like hybrid ICs, magnetic heads, microphones, ABS-sensors can be tested by microtomograpical methods. 

Commercial appHcations include substrates, fluidic devices, fine mesh screens, and magnetic head pads. 

O. Kohmoto, "Recent Developments of Thin Eilm Mateiials foi Magnetic Heads," IEEE Trans. Magn. 27(4), 3640 (1991). 

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 ... 

The FAS SAMs on the magnetic heads lead to a considerable improvement on tribological and corrosion-resistant properties, a high water contact angle, and electron charge adsorption-resistant property of the magnetic head. 

Tribology performances and applications of ordered molecular films have been a long-standing research subject in SKLT, the workplace for the authors of this book. Hu and Luo [42] prepared SAMs of fluoroalkylsilane (FAS) and poly-fluorealkylmethacrylate (PFAM) on the magnetic head of computer hard disk drivers. Experiment results show that the molecular films greatly improve the performance of the... 

In order to analyze the dynamic behavior of a magnetic head, time-dependent pressure should be calculated. This can be attained by solving the modified Reynolds equation including a squeezing term, i.e.. 

If we take Aq as the whole contact area of the magnetic head, and calculate the area of the segments in which film... 

Fig. 23—Area ratio Af,/Ao versus h, h is the flying height of the magnetic head Af, is the area where the flying height is below h and Aq is the total area of the head.

Wu, J. K. and Chen, H. X., Operator Splitting Method to Calculate Pressure of Ultra-Thin Gas Film of Magnetic Head/ Disk," Tribology, Vol. 23, No. 5, 2003, pp. 402-405 (in Chinese). 

Huang, R, Wang, H. Z., Xu, L. G., Meng, Y. G., and Wen, S. Z., Numerical Analysis of the Lubrication Performances for Ultrathin Gas Film Lubrication of Magnetic Head/Disk with a New Finite Difference Method, Proceedings of IMECE05, Paper No. IMECE2005-80707,2005. 

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. 1—The formation and measurement of molecular films (a) dipping of magnetic head immersing in solution, and (b) the process of TOF-SIMS to measure the AWA film.

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. 

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

From different solutions, Hu et al. [26,34] made SAMs over DLC films on magnetic heads. The samples were pulled out at different immersing times, cleared using an ultrasonic cleaner in octane solution, and then washed by DI water. After that, the samples dried by blowing nitrogen were annealed in a cleaning box for 30 min at a temperature of 120°C. 

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... 

The FAS SAMs have been grafted on magnetic heads by a robust covalent bond. The thickness, morphology, and the tri-... 

---