US2989472A - Ferrite with constricted magnetic hysteresis loop - Google Patents
Ferrite with constricted magnetic hysteresis loop Download PDFInfo
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- US2989472A US2989472A US616156A US61615656A US2989472A US 2989472 A US2989472 A US 2989472A US 616156 A US616156 A US 616156A US 61615656 A US61615656 A US 61615656A US 2989472 A US2989472 A US 2989472A
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- ferrite
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- magnetic hysteresis
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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
- thermomagnetic treatment in this connection, is meant the passing through a thermic cycle during the simultaneous presence of a magnetic longitudinal or transverse field.
- longitudinal or transverse field is, in this connection, to be understood as relative to the later measuring field; a longitudinal or transverse field, respectively, means that such field, during the thermomagnetic treatment, is parallel, respectively vertical, to the later measuring field.
- nickel-zincferrites with constricted hysteresis loop there exist nickel-zincferrites with constricted hysteresis loop, and it was claimed that, for instance, nickel-zinc-ferrites obtain a constricted hysteresis loop by the addition of manganese oxide and cobalt oxide.
- this claim is completely wrong; there are only very specific ferrites showing a constricted magnetic hysteresis loop which are, consequently, susceptible to thermomagnetic treatment similarly to the metals.
- the invention teaches the production of such ferrites of the nickel-zinc-ferrite system which can be subjected to thermomagnetic treatment of the above type, and are distinguished from hitherto familiar ferrites by the fact that, under the same manufacturing conditions, they have constricted hysteresis loops.
- ferrites with this characteristics in the nickel-zincferrite system must have a composition of at least 50 mol percent Fe O and a small addition of cobalt oxide.
- the addition of cobalt oxide is suitably determined between 0.1 and 5% by weight, calculated on the total basic batch of the nickelzinc-ferrite, expressed in metallic oxides.
- the invention has shown that it is particularly advantageous to choose the cobalt oxide content between 0.35 and 1% by weight, calculated on the basic batch.
- the nickel-zinc-ferrites in question which react strongly to the addition of cobalt oxide with a constricted loop, cover, in the three-component system Fe O -NiO-ZnO the area defined in FIG. 4 of the drawing by the pentagon A, B, C, D, E.
- the compositions of the corner points in percent by weight are:
- the above fern'tes may be prepared in the usual way,
- the powdered mixtures thus obtained may be given the desired form either immediately by dry pressing, extruding, or similar methods, or itmay be desirable, before ceramic forming, to proceed with a calcining firing of the whole or only a part thereof preferablybetween about 750 and 1150 C.
- the thus obtained parts are subjected to a sintering firing, suitably between 1250 C. and 1380 0., depending on the composition.
- the cooling takes place slowly, particularly in the temperature range between 700 C. and room temperature.
- the cooling speed is dependent upon the volume of the fired body. As a criterion, it may be stated that for a ring of about 46 mm. outside diameter, 34 mm. inside diameter,'and 10 mm. height, the cooling time from 700 C. to room temperature should take not less than 12 hours. If the rings are cooled rapidly, the effect of loop constriction does not occur. However, the constriction may be regained even for n'ngs cooled too rapidly, by re-heating them to a temperature of about 700 C., and cooling them slowly, as above described.
- the rings are cooled to room tepreature in the kiln during a period of approximately 24 hours.
- the ferrite rings thus obtained are provided with 0.4 mm. copper enamelled wire with windings as primary winding, and, as secondary winding, further 200 windings with 0.2 mm. copper enamelled 'wire are applied.
- the oscillographic photograph of this ferrite, produced in accordance with the invention, is shown in FIG. 1.
- the ferrite toroid of this example with 100 windings as a primary winding, is placed in a kiln. While heating to 600 C., and slow cooling for 12 hours to room temperature, a longitudinal magnetic field is maintained by means of the ring winding by l a. direct current, corresponding to a magnetic field strength of about 15 a.- windings/cm. If the hysteresis loop of the ferrite after this thermo-magnetic treatment is recorded in the same manner as described above, the result is analogous to that of metals when they are subjected to heat treatment in the longitudinal magnetic field; a complete change of the form of the hysteresis loop, as may be seen in FIG. 3 takes place.
- a process of making a ferrite body with a constricted hysteresis loop which ferrite body is susceptible to thermomagnetic treatment to change the hysteresis loop characteristics comprising providing a milled powder mixture consisting essentially of nickel oxide, from 1 to about 16.5% by weight of zinc oxide, 0.1 to 5% by weight of cobalt oxide and at least about 71% by weight and at least 50 mol percent of ferric oxide based on the total metal oxide content of the mixture, forming the powder mixture to the shape desired, sintering the shaped product at about 1250 C. to 1380 C., and thereafter, slowly cooling the sintered body from 700 C. down to room temperature over a period of at least about 12 hours.
- a process of making a ferrite body with a constricted hysteresis loop which ferrite body is susceptible to thermomagnetic treatment to change the hysteresis loop characteristics comprising providing a milled powder mixture consisting essentially of nickel oxide, from 1 to about 16.5% by weight of Zinc oxide, 0.1 to 5% by weight of cobalt oxide and at least about 71% by weight and at least mol percent of ferric oxide based on the total metal oxide content of the mixture, forming the powder mixture to the shape desired, sintering the shaped product at about 1250 C. to 1380 C., cooling the sintered product, thereafter reheating the sintered product to a temperature of about 700 C. and then slowly cooling to room temperature over a period of at least 12 hours.
- a fired body of a ferrite of the nickel-zinc ferrite system having a constricted magnetic hysteresis loop which ferrite body is susceptible to thermomagnetic treatment to change the hysteresis loop characteristics said ferrite containing about 0.1 to 5% by weight of cobalt oxide, 71 to 89% by weight and at least 50 mol percent of ferric oxide calculated on the total metal oxide content of the system, about '1 to 16.5% by weight of ZnO and the remainder comprising at least 1% by' weight, being NiO, said ferrite being obtained by gradually cooling the fired body from a temperature of about 700 C. down to room temperature over a period of at least 12 hours.
Description
June 20, 1961 o. ECKERT ETAL 2,989,472
FERRITE WITH CONSTRICTED MAGNETIC HYSTERESIS LOOP Filed on. 16. 1956 /VV /VV VVV V VVW LVV V V L V\NWMVVVWX\ 2w Y AAM QX QA M Z VW NW VVVVVVWVWVQ VWA/VL F1 5:. i INVENTORS BY M,MV M
United States Patent 2,989,472 FERRITE WITH CONSTRICTED MAGNETIC HYSTERESIS LOOP Oskar Eckert, Lauf (Pegnitz), and Georg Zerbes, Solingen,
Germany, assignors to Steatit-Magnesia Alr'tiengesellschaft, Lauf (Pegnitz), Germany, a corporation of Ger- Filed Oct. 16, 1956, Ser. No. 616,156 Claims priority, application Germany Oct. 20, 1955 4 Claims. (Cl. 252-425) low hysteresis losses, and, in general, small residual losses.
As indicated in the above cited literature, such materials may be subjected to thermomagnetic treatment. By thermomagnetic treatment, in this connection, is meant the passing through a thermic cycle during the simultaneous presence of a magnetic longitudinal or transverse field. The concept of longitudinal or transverse field is, in this connection, to be understood as relative to the later measuring field; a longitudinal or transverse field, respectively, means that such field, during the thermomagnetic treatment, is parallel, respectively vertical, to the later measuring field. Through this type of treatment, these ferromagnetic materials display a'substantial alteration of the form of the hysteresis loop, and hence a change of the magnetic properties.
Recently it was discovered that there exist nickel-zincferrites with constricted hysteresis loop, and it was claimed that, for instance, nickel-zinc-ferrites obtain a constricted hysteresis loop by the addition of manganese oxide and cobalt oxide. In this general form, however, this claim is completely wrong; there are only very specific ferrites showing a constricted magnetic hysteresis loop which are, consequently, susceptible to thermomagnetic treatment similarly to the metals.
The invention teaches the production of such ferrites of the nickel-zinc-ferrite system which can be subjected to thermomagnetic treatment of the above type, and are distinguished from hitherto familiar ferrites by the fact that, under the same manufacturing conditions, they have constricted hysteresis loops.
In accordance with the invention, ferrites with this characteristics in the nickel-zincferrite system must have a composition of at least 50 mol percent Fe O and a small addition of cobalt oxide. The addition of cobalt oxide is suitably determined between 0.1 and 5% by weight, calculated on the total basic batch of the nickelzinc-ferrite, expressed in metallic oxides. The invention has shown that it is particularly advantageous to choose the cobalt oxide content between 0.35 and 1% by weight, calculated on the basic batch. The nickel-zinc-ferrites in question, which react strongly to the addition of cobalt oxide with a constricted loop, cover, in the three-component system Fe O -NiO-ZnO the area defined in FIG. 4 of the drawing by the pentagon A, B, C, D, E. The compositions of the corner points in percent by weight, are:
The above fern'tes may be prepared in the usual way,
ICC
either by joint or partial precipitation, from corresponding metal salt solutions, or, as is customary in ceramic arts, they may be prepared for further processing by wet milling and mixing of the respective metal oxides. After drying, the powdered mixtures thus obtained may be given the desired form either immediately by dry pressing, extruding, or similar methods, or itmay be desirable, before ceramic forming, to proceed with a calcining firing of the whole or only a part thereof preferablybetween about 750 and 1150 C. The thus obtained parts are subjected to a sintering firing, suitably between 1250 C. and 1380 0., depending on the composition. To produce the constricted hysteresis loop in ferrites, in accordance with the invention, it is necessary that the cooling takes place slowly, particularly in the temperature range between 700 C. and room temperature. The cooling speed is dependent upon the volume of the fired body. As a criterion, it may be stated that for a ring of about 46 mm. outside diameter, 34 mm. inside diameter,'and 10 mm. height, the cooling time from 700 C. to room temperature should take not less than 12 hours. If the rings are cooled rapidly, the effect of loop constriction does not occur. However, the constriction may be regained even for n'ngs cooled too rapidly, by re-heating them to a temperature of about 700 C., and cooling them slowly, as above described.
One example of the invention follows hereafter:
In a steel ball mill are ground together 412.5 g. Fe O g. NiO, 12.5 g. ZnO, 3.25 g. CoO. After 6 hours of grinding, the slip is poured through a 4900 mesh screen (4900 meshes per square cm.) into aporcelain dish, and dried. The powder, thus obtained, is pressed, according to ceramic pressing techniques, into rings having dimensions of 59 mm. outside diameter, 35.8 mm. inside diameter, and 12 mm. height, the amount of pressure applied being about 0.5 to 1 ton/cm. The ferrite pieces thus obtained are sintered in a kiln at 1335 C. for two hours, whereupon the heat is shut off. The rings are cooled to room tepreature in the kiln during a period of approximately 24 hours. The ferrite rings thus obtained are provided with 0.4 mm. copper enamelled wire with windings as primary winding, and, as secondary winding, further 200 windings with 0.2 mm. copper enamelled 'wire are applied. The oscillographic photograph of this ferrite, produced in accordance with the invention, is shown in FIG. 1. One can distinctly recognize the loop constriction of the hysteresis loop, in contrast to a ferrite of the same basic batch but without the addition of cobalt oxide (FIG. 2).
The following experiment proves that ferrites produced in accordance with the invention are susceptible to thermomagnetic treatment:
The ferrite toroid of this example, with 100 windings as a primary winding, is placed in a kiln. While heating to 600 C., and slow cooling for 12 hours to room temperature, a longitudinal magnetic field is maintained by means of the ring winding by l a. direct current, corresponding to a magnetic field strength of about 15 a.- windings/cm. If the hysteresis loop of the ferrite after this thermo-magnetic treatment is recorded in the same manner as described above, the result is analogous to that of metals when they are subjected to heat treatment in the longitudinal magnetic field; a complete change of the form of the hysteresis loop, as may be seen in FIG. 3 takes place.
In analogous manner, heat treatment in the transverse magnetic field may be carried out with corresponding effect (see the above cited book by Bozorth) The technical progress obtained with such ferrites in accordance with the invention, may be seen in the following: with thermic longitudinal magnetization, for example, ferrites with distinctly rectangular hysteresis loop may be produced which are of importance to the entire fields of electronics and for magnetic amplification for telephone and high-frequency fields; with thermic cross magnetization, ferrites of high quality and a permeability independent of field strength may be produced, which are particularly suitable for the field of telecommunication.
We claim:
1. In a process of making a ferrite body with a constricted hysteresis loop which ferrite body is susceptible to thermomagnetic treatment to change the hysteresis loop characteristics, comprising providing a milled powder mixture consisting essentially of nickel oxide, from 1 to about 16.5% by weight of zinc oxide, 0.1 to 5% by weight of cobalt oxide and at least about 71% by weight and at least 50 mol percent of ferric oxide based on the total metal oxide content of the mixture, forming the powder mixture to the shape desired, sintering the shaped product at about 1250 C. to 1380 C., and thereafter, slowly cooling the sintered body from 700 C. down to room temperature over a period of at least about 12 hours.
2. In a process of making a ferrite body with a constricted hysteresis loop which ferrite body is susceptible to thermomagnetic treatment to change the hysteresis loop characteristics, comprising providing a milled powder mixture consisting essentially of nickel oxide, from 1 to about 16.5% by weight of Zinc oxide, 0.1 to 5% by weight of cobalt oxide and at least about 71% by weight and at least mol percent of ferric oxide based on the total metal oxide content of the mixture, forming the powder mixture to the shape desired, sintering the shaped product at about 1250 C. to 1380 C., cooling the sintered product, thereafter reheating the sintered product to a temperature of about 700 C. and then slowly cooling to room temperature over a period of at least 12 hours.
3. A fired body of a ferrite of the nickel-zinc ferrite system having a constricted magnetic hysteresis loop which ferrite body is susceptible to thermomagnetic treatment to change the hysteresis loop characteristics, said ferrite containing about 0.1 to 5% by weight of cobalt oxide, 71 to 89% by weight and at least 50 mol percent of ferric oxide calculated on the total metal oxide content of the system, about '1 to 16.5% by weight of ZnO and the remainder comprising at least 1% by' weight, being NiO, said ferrite being obtained by gradually cooling the fired body from a temperature of about 700 C. down to room temperature over a period of at least 12 hours.
4. A fired ferrite body as claimed in claim 3 wherein the cobalt oxide content is between 0.35 and 1% by weight of said ferrite.
References Cited in the file of this patent UNITED STATES PATENTS 2,452,530 Snoek Oct. 26, 1948 2,636,860 Snoek et a1. Apr. 28, 1953 2,640,813 Berge June 2, 1953 2,723,239 Harvey Nov. 8, 1955 2,73 6,708 Crowley Feb. 28, 1956 FOREIGN PATENTS 154,192 Australia Nov. 17, 1953 751,623 Great Britain July 4, 1956 756,374 Great Britain Sept. 5, 1956 1,125,577 France July 12, 1956 OTHER REFERENCES R.C.A. Review, September 1950, vol, 11, No. 3, pp. 321-363.
Weil: Comptes Rendus, vol. 234, pp. 1351 and 1352 (1952).
Wijn et al.: Philips Tech. Review, vol. 16, No, 2, pp. 49-58 (August 1954).
Bozorth et al.: Physical Review, vol. 99, pp. 1788- 1798 (September 15, 1955).
Claims (1)
- 3. A FIRED BODY OF A FERRITE OF THE NICKEL-ZINC FERRITE SYSTEM HAVING A CONSTRICTED MAGNETIC HYSTERESIS LOOP WHICH FERRITE BODY IS SUSCEPTIBLE TO THERMOMAGNETIC TREATMENT TO CHANGE THE HYSTERESIS LOOP CHARACTERISTICS, SAID FERRITE CONTAINING ABOUT 0.1 TO 5% BY WEIGHT OF COBALT OXIDE, 71 TO 89% BY WEIGHT AND AT LEAST 50 MOL PERCENT OF FER-
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DEST10447A DE1057254B (en) | 1955-10-20 | 1955-10-20 | Process for the production of ferromagnetic ferrite bodies with a constricted hysteresis loop |
DEST10460A DE1057255B (en) | 1955-10-20 | 1955-10-24 | Process for the production of ferromagnetic ferrite bodies with a constricted hysteresis loop |
Publications (1)
Publication Number | Publication Date |
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US2989472A true US2989472A (en) | 1961-06-20 |
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Application Number | Title | Priority Date | Filing Date |
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US616156A Expired - Lifetime US2989472A (en) | 1955-10-20 | 1956-10-16 | Ferrite with constricted magnetic hysteresis loop |
US616490A Expired - Lifetime US2929787A (en) | 1955-10-20 | 1956-10-17 | Ferrite with constricted magnetic hysteresis loop |
US616817A Expired - Lifetime US2989473A (en) | 1955-10-20 | 1956-10-18 | Ferrite with constricted magnetic hysteresis loop |
Family Applications After (2)
Application Number | Title | Priority Date | Filing Date |
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US616490A Expired - Lifetime US2929787A (en) | 1955-10-20 | 1956-10-17 | Ferrite with constricted magnetic hysteresis loop |
US616817A Expired - Lifetime US2989473A (en) | 1955-10-20 | 1956-10-18 | Ferrite with constricted magnetic hysteresis loop |
Country Status (5)
Country | Link |
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US (3) | US2989472A (en) |
DE (2) | DE1057254B (en) |
FR (1) | FR1160057A (en) |
GB (1) | GB849217A (en) |
NL (1) | NL96342C (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3514405A (en) * | 1965-08-10 | 1970-05-26 | Siemens Ag | Ferromagnetic switching core of ferrite with rectangular hysteresis loop and process for the production thereof |
US3526599A (en) * | 1967-05-25 | 1970-09-01 | Nippon Electric Co | Samarium oxide containing nickel-zinc ferrite |
US3533949A (en) * | 1967-11-21 | 1970-10-13 | Bell Telephone Labor Inc | Heat treating method for obtaining a ferrite with a high muq product |
US3609083A (en) * | 1970-03-17 | 1971-09-28 | Bell Telephone Labor Inc | Heat treatment of nickel zinc cobalt ferrite |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3081264A (en) * | 1958-04-09 | 1963-03-12 | Matake Kurokawa | Method of preparing a magnetic recorder powder |
US3072576A (en) * | 1958-05-27 | 1963-01-08 | Aladdin Ind Inc | Ferrites having rectangular hysteresis loops and method for manufacture of same |
DE1182129B (en) * | 1958-06-04 | 1964-11-19 | Licentia Gmbh | Process for the production of a magnetic core material with an almost rectangular hysteresis loop |
US3055832A (en) * | 1960-06-10 | 1962-09-25 | Ampex | Magnetically annealed ferrite material |
DE1696456B1 (en) * | 1965-03-24 | 1970-11-12 | Telefunken Patent | Process for the production of a substoechiometric ferrite with an almost rectangular, temperature-stable hysteresis loop for switching ring cores |
JPS5231555B1 (en) * | 1967-07-25 | 1977-08-16 |
Citations (8)
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US2452530A (en) * | 1943-05-15 | 1948-10-26 | Hartford Nat Bank & Trust Co | Magnetic core |
US2636860A (en) * | 1944-07-06 | 1953-04-28 | Hartford Nat Bank & Trust Co | Magnetic core |
US2640813A (en) * | 1948-06-26 | 1953-06-02 | Aladdin Ind Inc | Reaction product of a mixed ferrite and lead titanate |
US2723239A (en) * | 1952-09-29 | 1955-11-08 | Rca Corp | Ferrospinel compositions |
US2736708A (en) * | 1951-06-08 | 1956-02-28 | Henry L Crowley & Company Inc | Magnetic compositions |
GB751623A (en) * | 1953-11-27 | 1956-07-04 | Steatite Res Corp | Improvements in or relating to ferromagnetic ceramic bodies |
GB756374A (en) * | 1952-11-08 | 1956-09-05 | Licentia Gmbh | A method for the manufacture of ferrite cores |
FR1125577A (en) * | 1955-05-03 | 1956-11-02 | Lignes Telegraph Telephon | Ferromagnetic materials with rectangular hysteresis cycle |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL63875C (en) * | 1943-07-01 | |||
US2565861A (en) * | 1947-09-26 | 1951-08-28 | Rca Corp | Magnetic materials |
GB669571A (en) * | 1948-03-27 | 1952-04-02 | Philips Electrical Ind Ltd | Improvements in or relating to magnet cores for electromagnetic devices |
US2549089A (en) * | 1948-12-15 | 1951-04-17 | Rca Corp | Mixed ferrite compositions, including lithium ferrite |
NL82277C (en) * | 1954-01-12 | |||
FR1110334A (en) * | 1954-07-13 | 1956-02-10 | Improvements to such ferromagnetic materials | |
FR1127577A (en) * | 1955-06-07 | 1956-12-19 | Schlumberger Prospection | Improvements to shaped charge devices used for perforation |
-
0
- NL NL96342D patent/NL96342C/xx active
-
1955
- 1955-10-20 DE DEST10447A patent/DE1057254B/en active Pending
- 1955-10-24 DE DEST10460A patent/DE1057255B/en active Pending
-
1956
- 1956-10-16 US US616156A patent/US2989472A/en not_active Expired - Lifetime
- 1956-10-17 US US616490A patent/US2929787A/en not_active Expired - Lifetime
- 1956-10-18 US US616817A patent/US2989473A/en not_active Expired - Lifetime
- 1956-10-19 GB GB31915/56A patent/GB849217A/en not_active Expired
- 1956-10-19 FR FR1160057D patent/FR1160057A/en not_active Expired
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2452530A (en) * | 1943-05-15 | 1948-10-26 | Hartford Nat Bank & Trust Co | Magnetic core |
US2636860A (en) * | 1944-07-06 | 1953-04-28 | Hartford Nat Bank & Trust Co | Magnetic core |
US2640813A (en) * | 1948-06-26 | 1953-06-02 | Aladdin Ind Inc | Reaction product of a mixed ferrite and lead titanate |
US2736708A (en) * | 1951-06-08 | 1956-02-28 | Henry L Crowley & Company Inc | Magnetic compositions |
US2723239A (en) * | 1952-09-29 | 1955-11-08 | Rca Corp | Ferrospinel compositions |
GB756374A (en) * | 1952-11-08 | 1956-09-05 | Licentia Gmbh | A method for the manufacture of ferrite cores |
GB751623A (en) * | 1953-11-27 | 1956-07-04 | Steatite Res Corp | Improvements in or relating to ferromagnetic ceramic bodies |
FR1125577A (en) * | 1955-05-03 | 1956-11-02 | Lignes Telegraph Telephon | Ferromagnetic materials with rectangular hysteresis cycle |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3514405A (en) * | 1965-08-10 | 1970-05-26 | Siemens Ag | Ferromagnetic switching core of ferrite with rectangular hysteresis loop and process for the production thereof |
US3526599A (en) * | 1967-05-25 | 1970-09-01 | Nippon Electric Co | Samarium oxide containing nickel-zinc ferrite |
US3533949A (en) * | 1967-11-21 | 1970-10-13 | Bell Telephone Labor Inc | Heat treating method for obtaining a ferrite with a high muq product |
US3609083A (en) * | 1970-03-17 | 1971-09-28 | Bell Telephone Labor Inc | Heat treatment of nickel zinc cobalt ferrite |
Also Published As
Publication number | Publication date |
---|---|
DE1057255B (en) | 1959-05-14 |
NL96342C (en) | |
DE1057254B (en) | 1959-05-14 |
GB849217A (en) | 1960-09-21 |
US2929787A (en) | 1960-03-22 |
FR1160057A (en) | 1958-07-07 |
US2989473A (en) | 1961-06-20 |
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