Recording performance and magnetic characteristics of sputtered cobalt-nickel-tungsten films

Sputtered films of various CoNiW compositions were evaluated as to magnetic properties. These evaluations indicate the existence of an optimum tungsten content (25% by wt.) for maximum coercive force of 650 oe at a thickness of 750 Å. The hysteresis squareness (Mr/Ms) and coercivity squareness (S*) were 0.78 and 0.93, respectively, and were not altered by tungsten additions at or below 25%. A selected CoNiW composition was evaluated relative to basic digital recording performance and compared to current oxide coatings. The CoNiW films exhibit approximately 15 dB SNR improvement relative to gamma Fe2O3coatings. The recording performance of sputtered discs based on areal density capability is at least 3 times that of current oxide coatings; i.e.. 1.02 × 10⁶bits per cm²and 3.66 × 10⁶bits per cm²for oxide and sputtered metal films, respectively.