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 (M
r
/M
s
) 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 Fe
2
O
3
coatings. 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 × 10
⁶
bits per cm
²
and 3.66 × 10
⁶
bits per cm
²
for oxide and sputtered metal films, respectively.