US2989477A

US2989477A - Ferrite with constricted magnetic hysteresis loop

Info

Publication number: US2989477A
Application number: US622198A
Authority: US
Inventors: Eckert Oskar
Original assignee: Steatit Magnesia AG
Current assignee: Steatit Magnesia AG
Priority date: 1955-11-21
Filing date: 1956-11-14
Publication date: 1961-06-20
Anticipated expiration: 1978-06-20
Also published as: FR1163981A; GB849219A; US2989479A

Description

June 1961 o. ECKERT 2,989,477

FERRITE WITH CONSTRICTED MAGNETIC HYSTERESIS LOOP Filed Nov. 14, 1956 2 SheetsSheet 1 AYAYAYAV E5 5 NAVAAVVA 35 25' M W AMMAA .zfiwAAAAA/wAm/ W M A #1224; INVENTOR.

O. ECKERT June 20, 1961 FERRITE WITH CONSTRICTED MAGNETIC HYSTERESIS LOOP 2 Sheets-Sheet 2 Filed Nov A AAA w TAAA INVENTOR.

0.12%? [CK 57- Maw BY WC United States Patent Ofice 2,989,477 Patented June 20, 1961 2,989,477 WITH CONSTRICTED MAGNETIC HYSTERESIS L001? Oskar Eckert, L'auf (Pegnitz), Germany, assignor to Steafit-Magnesia Ak'tiengesellschaft, Lauf (Pegnitz), Germany, a corporation of Germany Filed Nov. 14, '1956, Ser. No. 622,198 Claims priority, application Germany Nov. 21, 1955 Claims. (Cl.252-'62.'5)

Ferromagnetic metals with constricted hysteresis loops (see, for example, Bozorth, Ferromagnetism, published by Nostrand Co., Inc., 1951, pages 498 to 499), have, as is well known, at small field strength within the constriction area, constant permeability, i.e., permeability independent of the field strength equal to the initial permeability, very 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 trans verse 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.

This invention is based on the discovery that it is possible to manufacture specific ferrites showing a constricted magnetic hysteresis loop which are, consequently, capable of thermomagnetic treatment similarly as for metals.

The invention teaches the production of such ferrites of the copper-zinc and copper-cadmium ferrite systems 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 characteristic in the copper-zinc and copper-cadmium ferrite systems 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 copper-zinc or copper-cadmium ferrite, expressed in metallic oxides. The invention has shown that it is particularly advantageous to choose the cobalt oxide content between 0.35 and 1.5% by weight, calculated on the basic batch. The copper-zinc and copper-cadmium ferrites in question, which react strongly to the addition of cobalt oxide with a constricted loop, cover, in the threecomponent system Fe O -NiO-ZnO the area defined in the attached diagrams of FIGS. 3 and 4 by the quadrangles A, B, C, D. The compositions at the corners in percent by weight, are:

The above ferrites may be prepared in the'usual way, either by joint or partial precipitation, from correspond: ing 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. The powdered mixtures thus obtained, after drying, maybe given the desired form either immediately by dry pressing, extruding, or similar methods, or it may be desirable, before ceramic forming, to proceed with a calcining firing of the entire mass or only a part thereof, preferably be-' tween 750 C. and 1200 C. The formed parts are sintered, depending on the composition, at temperatures between 1180 C. and 1350" C. To produce the constricted hysteresis loop in ferrites, in accordance with 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 efiect of loop constriction does not occur. However, the constriction may be regained even for rings' cooled too rapidly, by re-heating them to a temperature of about 700 C., and cooling them slowly, as above described.

Examples of the invention follow hereafterz (a) For the system CuO-ZnO-Fe O In a steel bal mill are ground together 412.5 g. Fe O 375 g. CuO, 50 g. ZnO, 3.25 g. CoO.

(b) For the CuO-CdO-Fe O porcelain 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 t./cm. The ferrite raw-pieces, thus obtained, are sintered in a kiln at 1320 C. for two hours, whereupon the heat is shut off. The rings are cooled to room temperature in the kiln during a period of approximately 24 hours. The ferrite rings thus obtained are provided with 0.4 mm. copper enameled wire with windings as primary winding, and, as secondary winding, further 200 windings with 0.2 mm. copper enameled wire are applied. In the oscillographic photograph of this ferrite, produced in accordance with the invention, which is shown in FIG. 2a, one can distinctly recognize the loop constriction of the hysteresis loop.

The following experiment proves that ferrites produced in accordance with the invention are susceptible to thermomagnetic treatment:

A ferrite toroid as prepared in the examples 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 system: In a steel ball mill 487.5 g. Fe O 875 g. CuO, 25 g. CdO and 3.2-5 'g.-'

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 thermornagnetic treatment is recorded in the same 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 takes place, as may be seen in FIGS. la and 2b. 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.

I claim:

1. A ferrite with a constricted magnetic hysteresis loop selected from the systems consisting of the copper-, zinc-,

iron oxide system and the copper-, cadmium iron oxide system containing a small amount of cobalt oxide, the iron oxide in said ferrite comprising at least 50 mol percent of the composition expressed as metal oxides and containing about 62.5 to 91% by weight of ferric oxide, about 1% to 30% by weight of CuO, about 0.1 to 5% by weight of C00, and the remainder consisting essentially of a metal oxide selected from the group consisting of ZnO and CdO.

2. A ferrite as defined in claim 1 containing between 0.35 and 1.5% by weight, of cobalt oxide.

3. A ferrite as defined in claim 2 in which the ferrite is of the copper-, zinc, iron oxide system, the proportion, by weight of copper oxide, zinc oxide and iron oxide being within the area A-B-C-D of FIG. 3 of the drawing, the corners of area A-B-C-D being as follows:

A=70% Fe 0 30% CuO, 0% ZnO, by weight,

B=70% Fe O 1% CuO, 29% ZnO, by weight,

C=91% Fe O 1% CuO, 8% ZnO, by weight,

=89% F8203, 11% CuO, 0% ZnO, by weight.

4. A ferrite as defined in claim 2 in which the ferrite is of the copper-, cadmium-iron oxide system, the proportions by weight of copper oxide, cadmium oxide and iron oxide being within the area ABCD of FIG. 4 of the drawing, the corners of area A,B,C,D, being as follows:

A=70% Fe O 30% CuO, 0% CdO, by weight, B=62.5% Fe O 1% CuO, 36.5% CdO, by weight, C=91% F6203, 1% CuO, 8% CdO, by weight, D=89% Fe O 11% CuO, 0% CdO, by Weight.

5. A process for preparing ferrites selected from the class consisting of copper-zinc-iron ferrites containing copper, zinc and iron oxides within the limits defined by area ABCD of FIG. 3 of the drawing plus 0.1 to 5% by weight of cobalt oxide and copper-cadmium-iron ferrites containing copper, cadmium and iron oxides within the limits defined by the area ABCD of FIG. 4 of the drawing plus 0.1 to 5% by weight of cobalt oxide comprising preparing a powdered composition consisting essentially of ferric oxide, copper oxide, cobalt oxide and an oxide selected from the group consisting of zinc oxide and cadmium oxide in the proportions required to provide an oxide mixture of a composition within the areas specified with 0.1 to 5% by weight of cobalt oxide, molding said powder composition to shape, firing the molded body at about 1180 C. to about 1350 C., and thereafter slowly cooling the fired body from 700 C. down to room temperature over a period of at least about 12 hours to provide a ferrite body having a constricted hysteresis loop.

References Cited in the file of this patent UNITED STATES PATENTS 2,549,089 Hegyi Apr. 17, 1951 2,565,861 Leverenz et a1. Aug. 28, 1951 2,646,608 Boeke July 28, 1953 2,656,319 Berge Oct. 20, 1953 2,723,239 Harvey Nov. 8, 1955 2,736,708 Crowley Feb. 28, 1956 2,886,530 Greger May 12, 1959 FOREIGN PATENTS 645,056 Great Britain Oct. 25, 1950 682,838 Great Britain Nov. 19, 1952 735,375 Great Britain Aug. 17, 1955 OTHER REFERENCES Economos: J. American Ceramic Soc., July 1955, p. 242.

J. Institute of Electrical Engineers, Japan, November 1937, pp. 4, 5, 7; October 1939, p. 571; June 1939, pp. 276-279, 281.

Bozorth et al.: Physical Rev., September 15, 1955, pp. 1792, 1793.

Proceedings of the IRE, vol. 44, No. 10 (Ferrites Issue). October 1956, pages 1300, 1301, 1304, 105 and 1306.

Ferromagnetism," Bozorth, D Van Nostrand, 1951, pp. 498 and 499.

RCA Review, September 1950, p. 345.

Claims

1. A FERRITE WITH A CONSTRICTED MAGNETIC HYSTERESIS LOOP SELECTED FROM THE SYSTEMS CONSISTING OF THE COPPER-, ZINC-, IRON OXIDE SYSTEM AND THE COPPER-, CADMIUM IRON OXIDE SYSTEM CONTAINING A SMALL AMOUNT OF COBALT OXIDE, THE IRON OXIDE IN SAID FERRITE COMPRISING AT LEAST 50 MOL PERCENT OF THE COMPOSITION EXPRESSED AS METAL OXIDES AND CONTAINING ABOUT 62.5 TO 91% BY WEIGHT OF FERRIC OXIDE, ABOUT 1% TO 30% BY WEIGHT OF CUO, ABOUT 0.1 TO 5% BY WEIGHT OF COO, AND THE REMAINDER CONSISTING ESSENTIALLY