Ru Underlayer Elimination for CoPt-Based Sputtered Tape With Perpendicular Recording Toward 330 TB per Cartridge Product

A sputtered tape that uses a CoPt-based granular recording layer was developed for practical application in the next generation of large-capacity magnetic tapes. 1) First, disk media were prepared by depositing films onto glass substrates using an inline disk sputter machine in which the substrates were stationary facing the target, and the ability to control the crystalline orientation, the magnetic isolation, and the magnetic anisotropy of the recording layer, which are the important functions of the underlayer, was investigated. As a result, it was found that the medium with Co
₆₀
Cr
₄₀
(45 nm)/Co
₆₀
Cr
₄₀
-15 vol.% TiO
₂
(5 nm) as the underlayer has the same properties as the medium with the Ru underlayer. 2) Next, a sputtered magnetic tape with Co
₆₀
Cr
₄₀
(25 nm)/Co
₆₀
Cr
₄₀
-SiO
₂
(25 nm) as the underlayer deposited on a polymer film was prepared using a roll-to-roll sputtering machine. The ability to control the crystalline orientation and magnetic isolation of the magnetic recording layer was evaluated, and from the results it was found that a magnetic film with a granular structure was formed on the sputtered magnetic tape in which the c-axis of the magnetic crystal grains is oriented in the direction perpendicular to the film and the magnetic crystal grains are separated by the SiO
₂
amorphous phase. 3) Furthermore, when the recording properties of the sputtered magnetic tape with a Co
₆₀
Cr
₄₀
(25 nm)/Co
₆₀
Cr
₄₀
-SiO
₂
(25 nm) underlayer were compared with those of a magnetic tape for a linear tape-open (LTO) format eighth-generation tape cartridge (LTO 8), it was confirmed that the broadband signal-to-noise ratio of the sputtered tape with a Co
₆₀
Cr
₄₀
/Co
₆₀
Cr
₄₀
-SiO
₂
underlayer is 4.2 dB higher than that of the LTO 8 tape at a linear density of 300 kfci.