Inductive head

Metal in gap (MIG) or ferrite heads are produced with a combination of machining, bonding, and thin-film processes. Thin-film inductive heads are manufactured using thin-fihn processes similar those of semiconductor 1C technology (discussed in Chapter 19). The thin-film head production process is rather unusual, as it involves both very thin and very thick films. We choose to present here a detailed summary of the fabrication process of thin-film inductive heads with a single-layer spiral coil. This may serve, once again to, illustrate the centrally important role of electrochemical deposition in connection with modem information technology. 

Mr = remanent magnetization, 6 = layer thickness, d = head-to-medium spacing, Q = a value related to the field gradient of an inductive head ( -0.75),... 

An important application of soft materials is inductive and magnetoresistive recording heads [9]. The function of inductive head materials is to realize flux closure for reading and writing on recording media. Typical... 

Most thin-film inductive heads employ multilayer spiral coils to achieve large read back signals. This means that the copper plating and the hard cured photoresist steps must be repeated. Electrical coimection between the neighboring coil layers must also be implemented. Naturally, these steps greatly add to the complexity of the thin film head production. 

A magnetic recording head that uses magnetic flux flowing from and into the coil for read-write operations, is called an inductive head . Figure 6.4 shows a schematic illustration of an inductive head. 

Tsang C et al (1990) Gigabit density recording using dual-element MR inductive heads on thin-film disks. IEEE Trans Magn MAG-26 1689-1693... 

Magnetic read/write elements have evolved from wire-wound ferrite inductive heads to microfabricated thin-film structures. Today, separate read and write elements are used, with a thin-fihn inductive element for writing and magnetoresistive element for reading. The quest for ever-increasing read head sensi-... 

Thin-film inductive heads may be used for reading processes also. When used in the reading process, read heads intercept the magnetic field from the recorded magnetization pattern in magnetic recording medium and convert it into electrical signals, which are then detected and decoded. 

The structure of thin-film inductive recording heads results in the exposure to the environment of small areas of metal, often permalloy (Ni-20Fe), which is a relatively corrosion-resistant alloy. In fact, in-service corrosion of permalloy is not a problem and thin-film inductive heads have no history of corrosion-induced field failure. However, corrosion of permalloy can occur during manufacturing, leading to yield losses. 

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