Tham khảo tài liệu '21st century manufacturing episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 254 Computer Manufacturing Chap. 6 Inductive write head MR read element Figure Magnetoresistive head operation. This multilayer sandwich arrangement is shown in Figure . The copper write coil is shown at the top of this figure and the MR read element is further down the stack. The write coil is copper. It is laid down by the same photolithography and plating steps as described earlier. However now that it only has to perform the write function it is much thinner and easier to make than a head that must perform both the write and the read functions. The head requữes fewer copper coils material layers photolithography steps and tolerance controls. This in itself also leads to fewer complications in manufacturing and a better yield. The read element is nickel iron and is laid down by sputtering. The NiFe alloy exhibits a change in resistance as it passes over a magnetic field this is the MR effect. Shielding layers protect the element from other magnetic fields. One shield is shown to the left of the MR sensor in Figure . The other shield is actually merged with and part of the write coil. Further developments in the material itself lead to the giant MR effect. The pickup sensor is a multilayer sandwich with a thin metal interlayer able to respond to even smaller magnetic fields. As before an inductive write element writes bits of information to magnetically biased regions within radially concentric tracks on the disc. When it is necessary to read the data back the MR sensor is used rather than another inductive head. The MR sensor picks up this magnetic transition or flux reversal between bits causing the magnetization in the MR sensor to read current is indicated inFigure620. This rotation is detected as a resistance change by a precision amplifier which then produces a stronger signal to the disc drive output. Management of Technology 255 Figure 6-20 Magnetoresistive head design. MANAGEMENT OF TECHNOLOGY The Culture and History
