The coating consists of magnetic particles, a binder to contain and disperse the particles, and lubricants to ease the motion of the tape and abrasives to reduce the wear of the tape. The magnetic particles are acicular (elongated) with a typical dimension of 250 nm in length and 50 nm in width and are of single domain particles, which can be easily magnetized parallel to their long axis. This arrangement is mainly used in conventional longitudinal magnetic recording, as shown in Figure 1.3a.

(a)

Figure 1.3: Schematic diagrams of arrangments of acicular magnetic particles for (a) longitudinal and (b) perpendicular magnetic recording tapes .

However, the areal densities are limited in the longitudinal magnetic recording. Hence, efforts have been made to fabricate tapes for perpendicular recording in which the long axes of the particles are aligned perpendicular to the surface as shown in Figure 1.3b. This arrangement provides high recording densities despite several difficulties which have been not addressed in the development of perpendicular magnetic recording.

(b)