Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/562—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F10/00—Thin magnetic films, e.g. of one-domain structure
  • H01F10/08—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers
  • H01F10/10—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition
  • H01F10/12—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being metals or alloys
  • H01F10/14—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being metals or alloys containing iron or nickel
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
  • H01F41/24—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids
  • H01F41/26—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids using electric currents, e.g. electroplating

Definitions

• the present invention relates generally to an improved magnetic fi-lm particularly adapted for use as a memory element in a data processing system, and more particularly to an improved technique for electrolytically depositing magnetic films of this type which consist essentially of a ternary alloy of nickel-iron-molybdenum.
• the films exhibit properties which permit switching at the lowest reasonable energy requirement possible, the energy level being consistent with the stability of the memory film or core. It is also generally desirable that the film have a composition which provides for a minim-a1, if any, magnetostriction, and in addition it is generally preferable that the magnetocrystalline anisotropy be substantially zero. It has been found that memory films having a very low or substantially zero co-eificient magnetostriction are desirable from the standpoint of stability, consistency, and uniformity in switching, and it has been further found that there is more freedom of physical arrangement of film devices if the magnetocrystalline anisotropy is zero.
• the optimum values of H normally lie between 1.0 and 2.0 oersteds, this value permitting rotational switching of the core at a relatively low magnitude of energy with the entire switching operation being accomplished with a lower overall energy requirement than would otherwise be necessary with films having significantly higher H values.
• the H values are sufiiciently high so that the films are not readily disturbed by stray magnetic fields of modest or moderate intensity. The system aspects are accordingly not adversely affected.
• the H values are likewise important, this figure relating to the coercive field of the film.
• the value of H should be somewhat less than value of I-I the range of the H /H ratio values preferably being 0.5 and 1. With this particular ratio range, and with presently available switching equipment, switching techniques utilized and the like, it has been found that the switching characteristics of a film having these characteristics are very useful. When the films are inverted, that is, the value of H exceeds that nited States atent value of H the films produced have been found to generally exhibit poor rotational switching characteristics. In addition, it has been generally found that poor dispersion exists in inverted films,
• an improved electroplating technique for the formation of thin nickel-iron-molybdenum films.
• the most important feature of the invention is the provision of a critical range of current density values which may be employed in order to prepare the improved nickel-iron-m-olybdenum films, these films having low and controlled values of H, together with optimum values for the ratio of H
• the resultant magnetic members have been found to have unusually high H values, these values being substantially higher than those achieved in connection with the present invention and ranging up to about 5 oersteds.
• a plating solution is prepared including nickel sulfate, ferrous sulfate, together with sodium molybdate, these materials being included in an acid plating bat-h along with certain conventional plating bath additives.
• These additives including the citric acid, saccharin, sodium lauryl sulfate, and sodium chloride are considered as conventional additives only, these being utilized in order to enhance the plating characteristics of and to control the ultimate plating of the film, and to otherwise control or modify various characteristics of plating.
• These additives are conventional in the planting art and do not in and of themselves provide a part or portion of the present invention, and it will be appreciated that other specific plating additives may be employed in order to achieve the results of the present invention.
• the current density employed ranges from bet-ween 6 and 1 2 ma./cm. and preferably is about 7 to 10 ma./cm. While the current density has been found to essentially control the rate at which the deposit is formed upon the substrate, it has been further found that the magnitude of current density has an affect upon the values of H along with the values of the ratio H /H Utilizing the techniques of the present invention, films are formed which have appropriate values of H and H making them partic ularly adaptable for use as magnetic memory elements in data processing systems.
• an electroplating bath is prepared having a composition range as is indicated herembelow:
• composition of the films prepared in accordance with this specific example was typically as follows:
• the anion of the nickel and iron salt and the cation of the molybdate salt is not particularly critical, it being appreoiated that the ratios of the materials in the bath are critical.
• the *Fe++/Ni++ concentration ratio ranges from between about 0.03 up to about 0.06, based upon the normalities of these ions in solution.
• the ratio M0O -/Ni++ ranges from between about 0.016 up to about 0.036. It will be appreciated that the various concentration ranges set forth herein will normally enable one to obtain the electroplated thin films in accordance with the present invention, these films having the desirable properties of magnetic thin films for memory applications.
• a one N solution of Fe++ includes one-half gram-molecularweight of the salt, for example, FeSO a one N solution of nickel Ni++ includes one-half gram molecular-weight of the salt, for example, NiSO a one N solution of MoO rincludes one-half gram-molecularweight of the salt, for example, Na MoO While the molybdenum is ultimately reduced from an oxidation state of 6 to the free metal, the normalities as expressed herein do not take account of the ultimate plating reaction through which the molybdenum goes. In other words, the term normality as used herein relates solely to the concentraction of the various ions of the individual salt solutions with sole reference being to the salt ions per se.
• any of the alkaline earth metals such as sodium moly-bdate, potassium molybdate, or the like may be utilized.
• the status of the pH of the bath has been indicated hereinabove. It will be observed that the bath is mildly on the acid side, this being desirable for plating the film-s in accordance with the technique of the present invention.
• the temperature range is not particularly critical, and it will be appreciated that good results may be achieved with holding the bath at substantially or near room temperature.
• the range of between 6 and 12 ma./cm. has been indicated. It will be appreciated that if a current density substantially lower than the minium indicated is employed no deposition Will occur. If, on the other hand, a current density is employed which substantially exceeds the maximum indicated hereinabove, films having high coercivity with distorted loops will develop. Accordingly, the range indicated is a preferred range, and in particular, a current density of about 6 ma./cm. is preferred.
• the substrate employed is preferably an insulating substance such as glass or plastic, ordinary micro-slide glass being preferred.
• the surface of the substrate is initially cleaned of all contaminants and is preferably polished to present a smooth plating surface.
• the substrate is then coated with a layer of gold or chromium-gold, the latter including a pair of layers wherein an initial layer of chromium is applied followed by the aplication of a layer of gold.
• the substrate surface treated may employ a plurality of individually spaced circular plated areas of a combined coating of about A. of chromium followed by 100 A. of gold.
• Conventional evaporative techniques are employed to coat the substrate.
• the film be produced in the presence of an external magnetic field, this field being applied during the plating operation.
• the application of such a magnetic field enhances the uniaxial anisotropy characteristics of the film.
• the field will be applied to the film being plated along the plane of the film.
• the field preferably is a strong field having a strength of about 25 to 35 oersteds.
• An aqueous acidic plating bath for preparation of electrolytically deposited nickel-iron-molybdenum films having the composition in the range 60-77%, 13- 24% and 10-46%, respectively, said bath consisting essentially of from about 0.45 N up to about 0.06 N in Ni++, from about 0.018 N up to about 0.029 N in Fe++, and from about 0.01 N up to about 0.017 N in M0O.f
• the plating bath as set forth in claim 3 being particularly chracterized in that the pH is between about 3 and 6.
• the pH range of said bath is maintained between about 3 and about 6, the current density employed in said bath ranges from about 6 ma. up to about 12 ma. for each cm. of plating surface and wherein an external magnetic field is applied to the film being plated along the plane of the film.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Power Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Electroplating And Plating Baths Therefor (AREA)

Priority Applications (6)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (5)

Cited By (5)

Citations (3)

• 0
  • BE BE638863D patent/BE638863A/xx unknown
  • NL NL299924D patent/NL299924A/xx unknown
• 1962
  • 1962-10-31 US US234518A patent/US3271274A/en not_active Expired - Lifetime
• 1963
  • 1963-10-15 DE DES87869A patent/DE1241226B/de active Pending
  • 1963-10-18 GB GB41225/63A patent/GB1039797A/en not_active Expired

Patent Citations (3)

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