Cr underlayer

Go Binary and Ternary Alloyed Thin Films. Most of the thin-film media for longitudinal and perpendicular recording consist of Co—X—Y binary or ternary alloys. In most cases Co—Cr is used for perpendicular recording while for the high density longitudinal media Co—Cr—X is used X = Pt, Ta, Ni). For the latter it is essential to deposit this alloy on a Cr underlayer in order to obtain the necessary in-plane orientation. A second element combined with Co has important consequences for the Curie temperature (T ) of the alloy, at which the spontaneous magnetisation disappears. The for... 

Optimizing the Cr layer also controls the crystal size and morphology. It was reported in 1986 (89,90) that the Cr underlayer thickness has a great influence on the coercivity of the Co—Ni—Cr layer. In most of the Hterature it can be found that with increasing Cr thickness the increases. Under ideal conditions and the right material combinations coercivities above 240 kA/m have been prepared. 

The ECL reaction can occur at room temperature in aqueous buffered solutions and in the presence of dissolved 02 or other impurities. To provide the electric field for ECL to occur at the detector region, a pair of connecting floating Pt electrodes (50 pm wide, 50 pm apart, and 100 nm thick) has been used. To improve the adhesion of the Pt layer, a Cr underlayer was used. Unfortunately, Cr was corroded in the presence of CL [725]. 

Lubricani Carbon overcoat CoPtCrb magnetic layer 6 A ruthenium layer CoPtCrb magnetic layer Cr underlayer... 

Concerns about the corrosion of thin films resulted in the evaluation of Co—Pt alloys. Sputtered Co—Pt magnetic thin films containing 25% Pt and 500 A thick have a coercivity of 1700 Oe [154]. A co-ercivity higher than 3000 Oe was obtained with Co—Cr—Pt—B sputtered media [155] on 3000 A thick Cr underlayer (no intermediate layer is required). Boron, the fourth element, is added at an amount of about 3 to 7 at%. A coercivity of 4200 Oe was obtained for sputtered Co—Cr—Pt alloys for a thickness range between 100 and 350 A. These films require a Cr underlayer and a special intermediate layer composed of Co or Co—Cr—Ta [156]. 

Structure of a longitudinal thin film recording medium consists of a substrate, typically a borosilicate glass or an Al-Mg alloy about 1-2 mm in thickness, coated with an amorphous non-magnetic layer of NiP that is 5 10 m in thickness, a Cr underlayer approximately 100-150 nm in thickness, a CoGrTaPt magnetic layer approximately 20-30 nm in thickness and a carbon overcoat approximately 10-20 nm thick. Such a structure is depicted schematically in Figure 1.22 which represents a typical cross-sectional view of the layered structure of a hard disk medium. 

---