Thin films of a ternary Ni‐Fe‐P alloy suitable for use in computer memories have been electrodeposited from a sulfate bath containing sodium hypophosphite. Glass coated with conductive vacuum evaporated layers of chromium and gold was used as a substrate. Essentially nonmagnetostrictive films, 1200Aå thick and 3×3 in. in area, with coercivities of 2 oe and anisotropy fields of 3.5 oe were prepared reproducibly. The effects of hypophosphite ion in the plating solution on the deposit composition, cathode potentials, and magnetic properties of the films are discussed.

Thin films (1000-2000A) containing 6-20% lee, 1-15% As, balance Ni were electrodeposited from mixed nickel-ferrous sulfate solutions containing sodium arsenite. Arsenite concentration and ferrous sulfate concentration in the solution were related to the film composition and the magnetic properties.The effects of As in Ni-Fe films was found to be similar to those of P, i.e., Hc and Hk values were lower and switching times were much more rapid in the ternary films than in similarly prepared binary films. Quarternary alloy films of Ni-Fe-As-P are also described.This work is an outgrowth of earlier studies on the Ni-Fe-P and Ni-Fe-Mo film alloy systems which have already been reported (1,2). Electrodeposited thin films in the alloy system Ni-Fe-As have been investigated and evaluated as magnetic elements for computer memory use, and results are described. A limited amount of work in the quarternary system NiFe-As-P is also discussed.The objective of the over-all program has been the development of the electrodeposition method for preparation of films having controllable and reproducible magnetic properties.Experimental The substrates were 3 by 3 in. microcover sheet, 0.002-0.010 in. thick, coated with vacuum-evaporated layers of chromium and gold. Corning 7059 glass, 1 by 2 by 0.032 in. was also used. The depositions were carried out in rectangular Lucite cells which were fitted with removable cathode holders, permitting accurate alignment of the cathode to the cell. A uniform magnetic field of 30 oe surrounded the cell. Anodes were of nickel sheet. No agitation was used. The current density was normally 6 ma/cm 2 delivered by a constant-current power supply. The films were electrodeposited at room temperature from nickel and ferrous sulfate solutions of the Watts type, containing boric acid, sodium chloride, saccharin, and sodium lauryl sulfate.The compositions of the electrolytes are shown in Table I. Arsenic was introduced as sodium arsenite. Two series of solutions were made up. In one, the sodium arsenite concentration was varied, and in the other, the ferrous sulfate concentration was varied.Films were chemically analyzed as follows: A known film area is dissolved in 1:2 HNO~ and diluted to volume. Arsenic is determined on one aliquot colorimetrically by the molybdenum-blue method after lowtemperature evaporation of HNO3. Spectrophotometric measurements at 820 m~ were made on a Beckman DU. The method was calibrated with standard solutions in the range from 0.006 to 0.3 mg/100 cc. Dissolved film samples 1 by 2 in. in area, containing about 5% As, commonly gave readings in the 0.04 rag/100 cc range. Accuracy in the 5% As range is believed to be +-0.5%.Nickel and iron are determined on other aliquots colorimetrically as nickel dimethylglyoxime and iron Table I. Composition of plating solutions for the deposition of Ni-Fe-As alloy thin films Component Composition of Plating Solutions Concentration, (g/l) Series N Series P solutions solutions Preferred NiSO~ . 6H,20 218 218 218 FeSO4 9 7H_~O 3.0-8.1 6.0 6.0 NaAsO~ 0...