Write Heads

Inductive magnetic write (recording) head consists of three main structural parts  

Most (thin-film) inductive magnetic heads have a magnetic core and coil fabricated by electrodeposition using 

After the bottom pole and insulator, a microwinding Cu coil is electrode-posited [121]. The insulator has to be prepared for the electrodeposition of Cu. This preparation involves the deposition of Cr/Cu bilayer by sputtering or evaporation. First, a thin layer (10 nm) of Cr is deposited onto the insulator. The function of the Cr layer is to provide a bonding layer between the insulator and Cu. A thin (50-100 nm) layer of Cu seed layer is then sputter deposited on Cr layer to provide sufficient electrical conductivity for subsequent electrodeposition of Cu. Cu is electrodeposited using deposition-through-mask technique. After electrodeposition of Cu coil, an insulator layer is deposited between the coil and the top pole layer. The top Permalloy pole is electrodeposited in the same way as the bottom pole layer, on thin sputter-deposited Permalloy underlayer (50-100 nm). The top and bottom pole layers are in contact. Finally, Cu interconnect pads, about 25-pm thick, are electrodeposited. The entire structure, poles and coil, is protected by an overcoat, usually sputtered AI2O3. The dimensions 

Pole materials in new write heads should have the following properties [100, 121-124]  

Saturation induction (saturation flux density) Bs 2.0 T (/i well above that 

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Magnetooptic Materials. The appHcation of magnetooptic effects to optical memory systems, such as for laser beam writing and magnetooptic read, has been the subject of much research. Magnetooptic storage media offer the potential of storing over 120 Mbit/cm of information without contact of the read/write head which would thus be very competitive to floppy disks and tape. 

A high quahty version of a dye-sublimation printer has been developed specifically for color proofing. This device uses a laser writing head, rather than the typical thermal printhead, to produce higher resolution images. The device is capable of tme halftones, providing an accurate rendition of a printed page. It is, however, expensive both in equipment and materials cost. 

Figure 7 SFM image of a thin-fiim read-write head showing magnetic poles (dark rectangles) recessed 200 A.

Fig. 5 Schematic of the read/write head-magnetic disk interface.

The Fe-N /Ti-N nano-multilayers were prepared by using the magnetron-sputtering technique [34]. Si (111) wafers are used as the substrate. The multilayers have a total thickness of about 500 nm with alternately Fe-N and Ti-N layers (shown in Fig. 38). The Fe-N layer was the outermost layer and the Ti-N layer was the iimermost layer. The thickness of each layer was strictly controlled by the sputtering time. Table 4 shows the thickness of each layer of the samples. Because the multilayer sample was supposed to be used as the magnetic write head, the thickness of the nonferromagnetic Ti-N layer was not changed. 

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 %. 

Actually, read/write heads in combination represent somewhat older technology it should thus be remembered that in newer technologies, there is a clear trend toward using separate heads for reading and writing (2). 

The second contribution spans an even larger range of length and times scales. Two benchmark examples illustrate the design approach polymer electrolyte fuel cells and hard disk drive (HDD) systems. In the current HDDs, the read/write head flies about 6.5 nm above the surface via the air bearing design. Multi-scale modeling tools include quantum mechanical (i.e., density functional theory (DFT)), atomistic (i.e., Monte Carlo (MC) and molecular dynamics (MD)), mesoscopic (i.e., dissipative particle dynamics (DPD) and lattice Boltzmann method (LBM)), and macroscopic (i.e., LBM, computational fluid mechanics, and system optimization) levels. 

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