Growth Mechanism and Structure of Obliquely Evaporated Co–CoO Tapes

Abstract

The growth mechanism that determines the microstructure of obliquely evaporated Co-CoO tapes has been investigated. A preferred orientation relation hcp-Co 001 CoO 111 is found in the neighboring grains when the hcp-Co grains grow on top of the CoO. However, no preferred orientation is observed in the lower to middle part of the magnetic layer when the CoO grains grow on top of the hcp-Co. The structural properties of the Co-CoO tapes can be explained accordingly based on the preferred orientation relation.

Metal Evaporated Media

“…Within the columns, several Co crystallites gather to form chains aligned with the columnar shape, although there exist isolated crystallites too. The c-axes of the hcp-Co crystallites are not all parallel but tend to be aligned with the columnar direction (Ito et al, 2002(Ito et al, , 2004. This work also clearly shows the evolution of the microstructure through the film thickness.…”

“…In the upper part, the crystallites are thinner and shorter, and the Co chains branch off. The crystallite c-axis orientation also tends to be more random toward the top of the medium (Ito et al, 2004). Such evolution of microstructure through the film thickness is related to the continuous varying incidence deposition process.…”

“…The CoO underlayer promotes the growth of a smaller columnar structure and a better orientation of the Co crystallites (Ito et al, 2004;Maezawa et al, 1999). The latter has been explained by a preferred crystallite orientation relation between the Co and CoO grains, at the interface with the CoO underlayer (Ishida et al, 2000;Ito et al, 2004). A CoO underlayer, therefore, proves efficient in providing a barrier to undesired oxidation from the polyester substrate, and in improving the film columnar structure and the orientation of the Co crystallites.…”

“…However, the recording performances were consistently improved with a reduction of the medium thickness (Arisaka et al, 1991;Xu et al, 2001). With thicknesses increasing above 100 nm, the grain switching field distribution (SFD) significantly increases compared to thinner films (Arisaka et al, 1991), which might be associated to a degradation of the crystalline orientation of the Co crystallites at the surface of thick media (Ito et al, 2004). Thin magnetic layers are required for high density magnetic recording media.…”

“…It was found that the presence of the CoO underlayer does not alter the film saturation magnetization, but significantly increases the coercivity. The CoO underlayer promotes the growth of a smaller columnar structure and a better orientation of the Co crystallites (Ito et al, 2004;Maezawa et al, 1999). The latter has been explained by a preferred crystallite orientation relation between the Co and CoO grains, at the interface with the CoO underlayer (Ishida et al, 2000;Ito et al, 2004).…”