High recording performance of Co–Cr medium sputter-deposited at high Ar pressure and high substrate temperature

Abstract

Co–Cr films were prepared by sputter deposition at a high Ar pressure of 70 Pa with elevated substrate temperatures up to 400 °C. Films of 100 nm thickness were deposited using a 19 at. % Cr–Co target onto a well c-axis oriented Ti underlayer prepared on glass disk substrates. The perpendicular coercivity, Hc⊥, of the films increased from 660 to 1940 Oe with increasing temperature. The films with high Hc⊥ exhibited a dense fine microstructure with distinct grain boundaries. The recording performance of the disk samples were measured by using a metal in gap type ring head, comparing with that of conventional Co–Cr films deposited at a low Ar pressure of 0.2 Pa. It was found that the high pressure deposited Co–Cr film exhibited higher output by more than 2 dB at the densities below 320 kFRPI (flux reversals per inch) compared with the conventional film with the same high coercivity. The D50* of as high as 250 kFRPI and the highest recordable density of over 600 kFRPI were confirmed for the new type of Co–Cr film deposited at 70 Pa and at 400 °C. The noise level of the film, however, was slightly higher than that of conventional method films, disagreeing with the suggestion of the microstructure.