Recording density

Current research aims at high efficiency PHB materials with both the high speed recording and high recording density that are required for future memory appHcations. To achieve this aim, donor—acceptor electron transfer (DA-ET) as the hole formation reaction is adopted (177). Novel PHB materials have been developed in which spectral holes can be burnt on sub- or nanosecond time scales in some D-A combinations (178). The type of hole formation can be controlled and changed between the one-photon type and the photon-gated two-photon type (179). 

Since the increase in recording density has been by a factor of 1000. Based on this trend, an areal density of more than 300 Gbit/in. is predicted to... 

Fig. 29 —Head media space with recording density.

Seismic techniques, the reflection and refraction of sound or shock waves propagated through the earth, are also used to reveal details of the structure and interrelationship of various layers in the subsurface. The shock or sound waves record densities in the earth s surface that may indicate an oil or gas reservoir. Explosive charges or vibration devices are used to impart the required shock wave. 

Near-held optics, in which recording density depends only on the size diameter of the probe tip aperture ... 

The sliders are free to move vertically around their load point (i.e., point of attachment) and can also rotate about the pitch and roll axes, as illustrated in Figure 1.5(a). As the HDI spacing is reduced to a nanometer scale, novel slider shapes, as shown in Figure 1.5(h), are necessary to maintain HDD reliability. This will remain a major design problem for sliders having ultrahigh recording density capabilities. 

H. Takano, Y. Nishida, A. Kuroda, H. Sawaguchi, T. Kawabe, A. Ishikawa, H. Aoi, H. Muraoka, Y. Nakamura, and K. Ouchi, A practical approach for realizing high-recording density hard disk drives , paper CA-01, MMM/Intermag 2001, San Antonio, TX, January 7-11. 

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