US2970112A - Ferromagnetic materials with rectangular hysteresis cycle and method for their manufacture - Google Patents

Ferromagnetic materials with rectangular hysteresis cycle and method for their manufacture Download PDF

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US2970112A
US2970112A US577327A US57732756A US2970112A US 2970112 A US2970112 A US 2970112A US 577327 A US577327 A US 577327A US 57732756 A US57732756 A US 57732756A US 2970112 A US2970112 A US 2970112A
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oxide
mixture
zinc
manganese
percentage
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Pierrot Andre
Yves C E Lescroel
Grabowski Bogdan
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Lignes Telegraphiques et Telephoniques LTT SA
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
    • C04B35/265—Compositions containing one or more ferrites of the group comprising manganese or zinc and one or more ferrites of the group comprising nickel, copper or cobalt

Definitions

  • Such materials can be employed in magnetic recording devices known as memory devices, magnetic control members, magnetic amplifiers and the like.
  • materials according to the invention are generally used in the form of toroidal cores or at least of closed magnetic circuits without air-gap.
  • a substantially rectangular hysteresis cycle, plotted for a magnetising field practically reaching saturation is defined in the following terms:
  • fl zratio of remanent fiuxdensity to saturation flux density.
  • H i B zflux density when the field has the value H may be used in connection with a work cycle in which the field varies between'a maximum positive value H and a maximum negative value (H i B zflux density when the field has the value H,,,, in
  • AB -(m and AB *(rn in which AB ahd AH are small variations of the flux density and of the magnetising field in the vicinity of a given point, are respectively the slope of the curve representing the hysteresis cycle when the field passes through zero and the slope of the curve when the flux density passes through zero.
  • the magnetic permeability n is defined as the initial permeability in the demagnetised state.
  • the coefiicient of eddy-current losses F expressed in ohms per henry, referred to the frequency of 800 cycles: per second is measured between 100 and 200 kilocycles per second, for a field of 2 millioersteds and at a temperature of about 20 C. for the circuits, the cross-sec tion of which is about 0.3 square centimeter.
  • the magnetostrictive effect may be defined by the value of the coeflicient of magnetostriction at saturation A, which is obtained by extrapolating, for the demagnetised state, the curve of relative variation Al/l, in the applied field direction, of the length I of the sample, versus this field, plotted for very high field strengths.
  • the response time is defined by considering two windings, having negligible time constant, placed on a t core made of the magnetic material concerned; this core a current pulse the rising time of which is very short (for example, less than 0.1 microsecond) is app ied to one of the windings and causes the magnetising field' to. pass to the value (-H the response time 1 is the time, expressed in microseconds, necessary for the voltage produced in the other winding, starting from zero, to pass through a maximum-and return to 10% of the value of this maximum.
  • the object of the invention is to provide magnetic materials of the ferrite type having on the one hand: substantially rectangular hysteresiscycles with a coefficient of rectangularity ,B at least equal to 0.80; and on the other hand: high electrical resistivities at least equal to 10 ohms-cm, low eddy-current loss coefiicient F,, at most equal to 0.20.
  • i i The rectangularity of the cycle is obtained by starting from materials of the ferrite type with a negative magnetostriction coefficient, which are subjected to strains developed during a heat treatment by means of which a considerable linear shrinkage is produced, of at least 8%, and which may go up to 30%, this being one of the characteristics of the methodof the invention.
  • these materials have negligible eddy current losses, which makes it possible to use them at high frequency with very low response times 1 at most equal to microseconds.
  • the materials according to the invention have inductions at saturation B of the order of 2,500 to 4,500 gauss, at about 20 C., coercive fields H comprised between 1 and 4 oersteds, and coefficients of rectangularity ,B greater than 0.80.
  • the invention provides a method of manufacture of ferromagnetic materials of the ferrite type having a substantially rectangular hysteresis cycle, comprising preparing a homogeneous mixture of fine powders of ferric oxide, with oxides of manganese and cobalt, and if desired oxide of zinc; the molecular proportions of the various oxides in the mixture respectively being 50 to 56% for the ferric oxide; 22 to 47% for the manganese and cobalt oxides and 0 to 25% for the oxide of zinc; the ferric oxide varying between 53 and 56% when no zinc oxide is present and between 50 and 53% when 25 zinc oxide is used.
  • the method further comprises the steps of compressing the mixture into cores and heat treating at a temperature between 1200 C. and 1300 C. in a nitrogen atmosphere containing a small percentage of oxygen, followed by slow cooling carried out in an inert atmosphere.
  • manganese oxide is conventionally referred to the number of atoms of manganese; consequently, in the following description the manganese oxide will be conventionally represented by MnO, although, in practice, it is possible to use different oxides such as MnO Mn O and so forth.
  • hardening element any oxide of bivalent metal capable of forming with an oxide of trivalent metal, more particularly with iron oxide, a ferrite with a magnetostrictive coefficient of relatively high but negative value and, if necessary, modifying in an appreciable manner the constant of anisotropy K of the relatively soft ferrite in which it is in solution.
  • the invention will be more particularly described in the following on ferrites prepared from mixtures whose starting compositions correspond to the formula xFegO uMnO, vCoO, sZnO where x, u, v and s are the molecular percentages which satisfy the following relations and The Curie points 0;, of the final product obtained, are always higher than 150 C.
  • compositions indicated are starting compositions before the mixture of oxides-is reduced to. powder by grinding.
  • manganese and, if desired, zinc, cobalt oxide may be substituted for a portion of the manganese oxide.
  • the relatively soft ferrites in which the substitution mentioned above is made have a practically zero magnetostriction coefficient a In a ferrite of manganese- Zinc for which A is zero, it is necessary for a certain quantity of ferrous iron to be formed so that the ferrite Fe O may have a sufficient positive magnetostriction coefficient to cancel those of the other ferrites.
  • the constant of anisotropy of the ferrite is substantially increased, which results in an increase of the coercive field H
  • the formed ferrite has, on the other hand, a definitely negative magnetostriction coefficient which is a necessary condition in order that, after suitable treatment and determined consecutive shrinkage, it may have a substantially rectangular hysteresis cycle.
  • the relatively high iron content has two interesting consequences: on the one hand, an increase of the Curie point 6 and a better stability of the characteristics as a function of the temperature, and on the other hand, the saturation flux density is rather high, usually reaching values comprised between 2,500 and 4,500 gauss.
  • Figure 1 represents a practically rectangular hysteresis cycle.
  • a Figure 2 represents the molecular percentages of ferric oxide, as a function of the molecular percentages of zinc oxide, of a material in accordance with the invention.
  • Figure 3 represents the characteristics of a. material, in accordance with the invention, as a function of its content of cobalt oxide.
  • Figure 4 represents the same characteristics ina material of another composition.
  • Figure 5 represents the characteristics for another material as a function of its content of ferric oxide.
  • Figures 6, 7' and 8 respectively represent the hysteresis cycles corresponding to materials of different .com'positions.
  • cobalt in the mixture of oxides used in the preparation of a material in accordance with the invention are rather critical; especially for a particular content of zinc oxide, the content of ferric oxide must not differ from the optimum value by more than 3%.
  • a hatched zone is shown limited by the two curves C and C the points inside this zone indicate the contents of ferric oxide to be introduced into the starting mixture of oxides for a predetermined content of zinc oxide. I a.
  • Figure 2 shows that when the molecular percentage of zinc oxide is of the order of 20%, the most suitable molecular percentage of ferric oxide is close to 52.5%, whileit should be about 54% when there is no zinc oxide.
  • This optimum content of ferric oxide may vary slightly according to the molecular percentage of cobalt oxide which is present; in any case, the possible scope of variation of the molecular percentage of ferric oxide available is approximately 3%.
  • Figures 3 and 4 show the influence of the substitution of a certain number of C molecules for an equal number of MnO molecules upon the characteristics of e H B fora cycle corresponding to a field H, of 5 oersteds.
  • Figure 3 shows, for example, that p passes through a 52.5% F6203, 28.3% MnO, 19.2% ZnO when 4 C00 molecules are substituted therein for 4 MnO molecules. Then, the maximum value of 18,, is near 0.90.
  • the same characteristics B H ,8,, taken for a cycle corresponding to a field H of 5 oersteds, are plotted as a function of the contentof CoO molecules .which have been substituted for an equal quantity of iMnO molecules in the ferrite prepared from a mixture of the following composition:
  • the curves of Figure 5 represent as a function of the content x of Fe O the variations of the characteristics B H p for starting compositions comprising con- ;stant contents of cobalt oxide and zinc oxideand respec- .jtively equal to 4% and 10%; themaximum of fi is equal to 0.87 and occurs for a value of x equal to 53.5;
  • the curve for 3 is rather sharp and p is higher than 0.80 for x comprised between 53.3 and 54.2; the fiux density corresponding to a field H of 10 oersteds passes through a maximum at the same time as fi METHOD OF MANUFACTURE Composition and nature of oxides employed .;For the mixtures, ferric oxide (Fe O saline oxide of manganese (Mn O oxide of cobalt of zinc (ZnO) are used.
  • impurities are L meant products such as silica (SiO sulphur, alltali jmetals (Na, K), and so forth.
  • the ,black industrial cobalt'oxide must be preliminarilytreated, at 900 C., in order to eliminate its impurities and its humidity, and to bring it to a state near CoO.
  • G nd pifl The mixture of oxides is ground'or milled in anfapf intestinal device such as an iron grinder, with steel balls, usually for 12 to 48 hours, with a weight of distilled water equal to about twice the weight of the mixture.
  • Pressing H eat treatment The product so obtained is subjected to a heat treatment consisting of a heating lasting from 2 to 6 hours at a temperature comprised between 1,200 C. and 1,300 C. in a mixture of pure nitrogenand of 0 to 2% in volume of oxygen, followed by slow cooling carried out for about 15 hours in pure nitrogen.
  • Example 1 Figure 6 represents the hysteresis cycle taken in direct current for a maximum magnetising field H of 5 oersteds on a toroidal ferrite core having the following dimensions:
  • the annealing was carried out at 1,240 C., for four hours, in a mixture of pure nitrogen and of 1% of oxygen in volume, and cooling took place in pure nitrogen.
  • This material shows, for a cycle corresponding to a field H of 5 oersteds, the following characteristics:
  • This very low coefficient of eddy-current losses ensures the stability of the hysteresis cycle as a function of the frequency, and a preservation of the characteristics indicated, as a function of the frequency, up to very high values; consequently, it renders the response time very short. This is also one of the characteristics of the invention.
  • Example 2 Figure 7 represents the hysteresis cycle taken in direct .current for a maximum magnetising field H of 10 oersteds, on a toroidal ferrite core, the dimensions of Millimeters Outer diameter 34.5 eInner diameter 27.3 Height 5.4
  • Example Figure 8 represents the hysteresis cycle taken with difrect current for a maximum magnetising field H of 10 .oersteds on a toroidal ferrite core of the following di- "mensions:
  • the starting composition of the material corresponded 'toth'e following formula in molecular percentage.
  • the said mixture being composed of ferric oxide, of manganeseand cobalt oxides and oxide of zinc wherein inthe said mixture the sum of the molecular j pe'rcentage of 'the'manganese oxide, conventionally related to the number of atoms of manganese and the *percentage of cobalt oxide is between "22 and 47%, the molecular percentage of cobalt oxide is between 1 f'and 6%, the molecular percentage of zinc is between '-0 and 25% and the molecular percentage o'f-ferric-oxide is between 50 and 56%-, said ferricoxide 'va'r'ying het'ween 53 and 56% when the .zinc .oxide is 0% and-be- -;tween 5 0 and-53% when.25% zinc oxide is used, the 'relationship of the ferric oxide to *the
  • the said mixture being composed of ferric oxide, of manganese and cobalt oxides and oxide of zinc wherein in the said mixture the sum of the molecular percentage of the manganese oxide, conventionally related to'the number-of atoms of manganese and the percentage ofcobalt oxide is between, 22 and 47, the molecular percentage of cobalt oxide is between l and 6, the molecular percentage of zinc is between Oand 25 and the molecular percentage of ferric oxide is between 50and 56%, said ferric oxide varying between 53 and 56% when the zinc oxide is 0% and between 50 and 53% when 25% zinc oxide is used, the relationship of the ferric oxide tothe 'zinc oxide varying linearly between these values-whereby "there is produced a rectangularhysteresiscycle such that the ratio of remanent flux density to maximum fiuxdensity'is at least 0180

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US577327A 1955-05-03 1956-04-10 Ferromagnetic materials with rectangular hysteresis cycle and method for their manufacture Expired - Lifetime US2970112A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160576A (en) * 1959-11-16 1964-12-08 Steatit Magnesia Ag Method of producing thin ferromagnetic layers of uniaxial anisotropy

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS565046B1 (fr) * 1969-05-09 1981-02-03

Citations (13)

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US1086346A (en) * 1910-04-12 1914-02-10 Union Metal Mfg Co Combined pole and lamp-post.
US2179810A (en) * 1935-09-18 1939-11-14 Ig Farbenindustrie Ag Finely divided magnetic substance
US2535025A (en) * 1949-10-06 1950-12-26 Steatite Res Corp Process of treating ferrites
US2551711A (en) * 1943-07-01 1951-05-08 Hartford Nat Bank & Trust Co Manganese zinc ferrite core
US2565861A (en) * 1947-09-26 1951-08-28 Rca Corp Magnetic materials
US2579978A (en) * 1946-03-27 1951-12-25 Hartford Nat Bank & Trust Co Soft ferromagnetic material and method of making same
US2626445A (en) * 1950-06-07 1953-01-27 Steatite Res Corp Heavy-metal oxide resistors and process of making same
US2636860A (en) * 1944-07-06 1953-04-28 Hartford Nat Bank & Trust Co Magnetic core
US2715109A (en) * 1954-06-14 1955-08-09 Steatite Res Corp Ferromagnetic ceramic materials with hysteresis loops of rectangular shape
US2723239A (en) * 1952-09-29 1955-11-08 Rca Corp Ferrospinel compositions
FR1117385A (fr) * 1954-01-12 1956-05-22 Philips Nv Procédé de fabrication d'un noyau magnétique à cycle d'hystérésis pratiquement rectangulaire
US2886529A (en) * 1952-07-31 1959-05-12 Centre Nat Rech Scient Magnetic materials and their methods of manufacture
GB1033268A (en) * 1963-06-05 1966-06-22 Ciba Ltd New anthranilic acid amides and process for preparing same

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Publication number Priority date Publication date Assignee Title
DE756383C (de) * 1938-09-17 1952-10-20 Neosid Hansgeorg Pemetzrieder Verlustarme ferromagnetische Stoffe aus Metalloxyden fuer Hochfrequenzzwecke
US2640813A (en) * 1948-06-26 1953-06-02 Aladdin Ind Inc Reaction product of a mixed ferrite and lead titanate
GB721630A (en) * 1951-08-29 1955-01-12 Anorgana Gmbh Method for the production of ª†-fe o of improved magnetic properties

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1086346A (en) * 1910-04-12 1914-02-10 Union Metal Mfg Co Combined pole and lamp-post.
US2179810A (en) * 1935-09-18 1939-11-14 Ig Farbenindustrie Ag Finely divided magnetic substance
US2551711A (en) * 1943-07-01 1951-05-08 Hartford Nat Bank & Trust Co Manganese zinc ferrite core
US2636860A (en) * 1944-07-06 1953-04-28 Hartford Nat Bank & Trust Co Magnetic core
US2579978A (en) * 1946-03-27 1951-12-25 Hartford Nat Bank & Trust Co Soft ferromagnetic material and method of making same
US2565861A (en) * 1947-09-26 1951-08-28 Rca Corp Magnetic materials
US2535025A (en) * 1949-10-06 1950-12-26 Steatite Res Corp Process of treating ferrites
US2626445A (en) * 1950-06-07 1953-01-27 Steatite Res Corp Heavy-metal oxide resistors and process of making same
US2886529A (en) * 1952-07-31 1959-05-12 Centre Nat Rech Scient Magnetic materials and their methods of manufacture
US2723239A (en) * 1952-09-29 1955-11-08 Rca Corp Ferrospinel compositions
FR1117385A (fr) * 1954-01-12 1956-05-22 Philips Nv Procédé de fabrication d'un noyau magnétique à cycle d'hystérésis pratiquement rectangulaire
US2882236A (en) * 1954-01-12 1959-04-14 Philips Corp Method of manufacturing magnet cores having a substantially rectangular outline of hysteresis loop
US2715109A (en) * 1954-06-14 1955-08-09 Steatite Res Corp Ferromagnetic ceramic materials with hysteresis loops of rectangular shape
GB1033268A (en) * 1963-06-05 1966-06-22 Ciba Ltd New anthranilic acid amides and process for preparing same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160576A (en) * 1959-11-16 1964-12-08 Steatit Magnesia Ag Method of producing thin ferromagnetic layers of uniaxial anisotropy

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ES228280A1 (es) 1957-03-01
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