An electroplated 84Fe-5Ni-11Cu isotropic thin film for the cubic waffle-iron

The information storage media in the cubic waffle-iron memory is a square loop, isotropic, medium coercive force planar film called the overlay, which is placed in contact with ferrite posts. An 84Fe-5Ni-11Cu alloy has been developed to meet the requirements of the waffle-iron overlay. The film is electrodeposited on a specially prepared by by 0.040 inch copper substrate. The basic waffle-iron cell has an area of 30 mils by 30 mils, yielding a storage density in the film of 1100 b/in². The film has a coercive force of 10 Oe, 0.9 squareness ratio, 7000-Å thickness, and 0.52 Oe-μs switching coefficient. The preparation technique of the substrate has resulted in a 75-percent yield of films in which every bit output exceeds a level of 5 mV. Operational data has shown output uniformity to be maintained within ±10 percent. A corrosion study at 95°F and 90-percent humidity of eight protective coatings has resulted in the choice of Acryloid lacquer as the protective coating for the iron-rich alloy. This coating, which is applied evenly by a controlled dipping process, also provides electrical insulation between the film and the drive windings. Preliminary results of a six-month aging study at 60°C show no significant change in the hysteresis loop of the films.