Continuous Fabrication and Perpendicular Recording Characteristics of Co-Cr Magnetic Tape
A new sputtering source (named an SPT target) was modified so as to enable high-rate deposition and continuous fabrication of Co-Cr composite perpendicular recording media. In order to improve the orientation and crystallinity of the Co-Cr layer and the permalloy backlayer, the aperture position was optimized and a magnetic return path plate was added to the target. The Co-Cr tape medium deposited on a 9 m thick polyimide film using this modified sputtering source showed good high-density recording performance.
Self-epitaxial Co-Cr media: Preferable for fabrication by roll coater sputtering system
A roll coater system was investigated for establishment of a mass production system for Co-Cr perpendicular magnetic recording media. Improvements of the crystal orientation and the magnetic properties of Co-Cr films with new seed layers of Co-Cr itself are first described. In the light of these results, a Co-Cr film with a composition gradient in the growing direction but without any seed layer is proposed and its properties are discussed. It is found that the anisotropy field Hk can be remarkably increased for the film with a composition gradient over that of films with uniform composition. It is concluded that the newly developed Co-Cr film is very suitable for mass production by a roll coater because of its simplified process which requires no sputtering of any seed layers.
The Invariance of the Vacuum is the Invariance of the World
The following theorem is demonstrated: If the vacuum is invariant under the group generated by the space integral of the time component of a local vector current, then the Hamiltonian is invariant also. A similar theorem holds for the group generated by the space integral of a space component of a local axial-vector current.