Magnetic and recording characteristics of CoCrTa/Cr thin film media prepared by FT sputtering

Magnetic properties and media noise in CoCrTa/Cr longitudinal magnetic recording media prepared by facing targets (FT) sputtering were studied. All CoCrTa magnetic films in this study were deposited at an Ar gas pressure of 2 mtorr, and they were 500 Å in thickness. The coercivity of a film deposited on a substrate at room temperature depended strongly on Cr layer thickness and Ar gas pressure. The film with a Cr underlayer deposited at an Ar gas pressure as low as 0.2 mtorr in the thickness range from 100 to 1000 Å exhibited higher coercivity than one at Ar pressure as high as 10 mtorr. The coercivity of the film abruptly increased from 400 to 1100 Oe as a result of annealing at 400°C even for a time as short as 15 min. Media noise normalized according to the amplitude of an isolated pulse signal of a magnetic disk with CoCrTa/Cr films has been evaluated. Normalized media noise also depended on Ar gas pressure and the thickness of the Cr underlayer. Reduction in the media noise of films prepared at high Ar gas pressure with an increase of the Cr underlayer thickness seems to be due to the decrease in coupling force among ferromagnetic grains due to clear column formation in the microstructure of the Cr underlayer