Ferrite 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. 

A solution to eddy-current problem is the fabrication of heads with a combination of materials instead of a massive metallic body, there is only a metallic thin film in the gap of a ferrite head. Fig. 6.34. The magnetic flux produced by the ferrite ring is strongly enhanced in the most important area of the head by a thin film of a metallic alloy with high saturation magnetisation. Eddy currents are therefore limited by the film... 

Surface roughness of several polymeric materials was measured and compared with coefficients of friction of these materials with themselves, magnetic tape, and a Ni-Fe ferrite head. " Surface roughness from this data is important but not decisive parameter influencing the coefficient of friction. " ... 

Magnetic materials can be classified into two groups metal and alloy materials, and metal oxide materials represented by ferrites. We here describe the Mn-Zn ferrites, which are used, for example, as the magnetic heads in magnetic recording, focusing on the preparative processes and physical properties, which are closely related to the oxygen non-stoichiometry. 

In order to use Mn Zn ferrites as magnetic head materials, the materials have to show the following characteristics ... 

For high quality audio and v ideo recording where the recording medium is CrO or Co impregnated p-Fcyf.)-.. sputtered Scndust alloy films (9.ft wt < Si. 5.4 wl Al. balance Fe see also Table 61 and ferrites are used as head matenals. 

Parylene is used in the manufacture of high quality miniature stepping motors, such as those used in wristwatches, and as a coating for the ferrite cores of pulse transformers, magnetic tape-recording heads, and miniature inductors. 

Because of the size and the pressure of the vessel, austenitic stainless steel could not be used throughout, but must be applied on the inner surfaces of the ferritic material. This has been done by explosion plating of a 4 mm cladding on the base material prior to rolling the cylinder and forming the hemispherical head. For the flat cover and the sealing faces weldcladding was applied. 

Zeiss [48] describes a method for measuring sections of milled ferrite powder. The powder was mixed in 40 60 volume ratios with epoxy resin using a homogenizing head rotating at 25,000 rpm. The mixture was then poured into a 0.5 in diameter mold and cured at 60°C and 1000 psi to eliminate air bubbles. The casting was then polished in a vibratory polisher using 0.3 and 0.5 pm alumina in water. A photomicrograph of the polished section was used for subsequent analysis. 

Kakizaki, K., and Hiratuka, N., Magnetic properties and crystal structures of acicular barium ferrite particles, J. Magn. Soc. Jpn., 22(suppl. SI), 129, 1998. Lemke, J.U., Ultra high density recording with new heads and tapes, IEEE Trans. Magn., 15, 1561, 1979. 

The most important application of cubic ferrites, quantitywise, is the manufacture of coil- and transfomier-cores. In terms of numbers, recording and erasure heads for tape recorders, ferrite antennae for the frequency range 0.5 to 1.5 MHz and other components for high frequency technology are also important. 

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