Strain insensitive Ni-Co films over a wide composition range

The magnetic properties of vacuum deposited Ni-Co films have been studied as a function of film composition, film thickness, and substrate temperature. The experimental parameters ranged from 400-1000 Å for thickness 17-41-percent Ni for composition and room temperature to 300°C for the substrate temperature. It was found that the magnetoelastic strain coefficient approaches zero in the vicinity of 35-percent Ni in agreement with Tolman's result[1] and remains insensitive to film composition from 30-40- percent Ni. These results are in reasonably good agreement with calculations based on single crystal data and the expression of Callen and Goldberg [10]. The coercive force and anisotropy field are an order of magnitude larger than of nonmagnetostrictive Permalloy films. An unexpected result is an increased coercive field with increasing film thickness while the anisotropy field remains practically constant; the films become inverted at a critical thickness in the order of 750 Å For a wide variation of preparation parameters the crystallite size remained less than 100 Å     

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 prepared2 frac{1}/{2}by1 frac{1}/{4}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.