US2943913A

US2943913A - Ferromagnetic material and process

Info

Publication number: US2943913A
Application number: US684423A
Authority: US
Inventors: Brixner Lothar Heinrich
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1957-09-17
Filing date: 1957-09-17
Publication date: 1960-07-05
Anticipated expiration: 1977-07-05

Description

United States Patent C) FERROMAGNETIC MATERIAL AND PROCESS Lothar Heinrich Brixner, Wilmington, Del., assign'or to E. I. du Pont de Nemours and Company, Wilmington, -Del., a corporation of Delaware No Drawing. Filed Sept. 17, 1957, Ser. No. 684,423

4 Claims. (CI. 2358) This invention relates to a new ferromagnetic material.

Ferromagnetic materials might broadly be classified into two groups: those with low coercivities, and those with high coercivities. Materials of the former type are useful in transformers, magnetic amplifiers, memory cores, and microwave devices. The ferromagnetic materials with high coercivities are useful in permanent magnets.

The ferromagnetic material of this invention possesses an exceptionally high intrinsic coercive force, and it is represented by the empirical formula BaMnFe O This material is prepared by heating for from about onehalf hour to two hours at temperatures between 600 C. and 1000 C. Fe O and BaMnO, in a mol ratio of 6:1, thus simultaneously forming a new combination of barium manganese, iron and oxygen with the evolution of /2 mol of oxygen. The product obtained from the heating is then cooled, pulverized and compacted under pressure into a unitary mass of desired shape by pressing or extruding. This mass is subjected to firing for from 2 to hours, at temperatures between 1000 C. and 1300 C. In the practice of this invention, it is convenient and preferred to use commercially available reactants of the highest purity. X-ray analysis of the final product fails to indicate the presence of barium oxide, or any known manganese oxide, or other known manganese compounds. The material is crystalline and hexagonal in structure, and it shows pronounced magnetic anisotropy. The crystals are characterized by the following cell constants: a=5.88 A., c=23.02 A.

For a clearer understanding of the invention, the following specific example is given. This example is intended to be merely illustrative of the invention and not in limitation thereof. Unless otherwise specified, all parts are by weight.

Example 15.766 g. of BaMnO, and 58.94 g. of Fe O were thoroughly mixed and then passed through a 60-mesh screen. The mixture was fired at 1000 C. in air for /1 of an hour in a platinum crucible. After cooling to room temperature in air, the mixture Was ball milled with ethyl alcohol, dried, and passed through a ZOO-mesh screen. The powder was then hydrostatically pressed at 190,000 p.s.i. into a rod /2" in diameter by 1" in length. This rod was fired at 1150 C. for 4 hours in air, and then it was air quenched. The material thus produced was a compact rod which was useful as a magnet. The product thus prepared had a density of 5.11 g./cm. This figure was close to the theoretical value for the material. The rod was then tested for magnetic properties, using a Sanford-Bennett high field permeammeter from the Rubicon Company. The cylindrical rod was butted between the pole pieces of the permeammeter and subjected to the standard operation for obtaining the demagnetizing curve. The magnetic properties and resistivity were found to be as follows:

The high resistivity and high coercive force combined with high remanent magnetization make this new compound very valuable as a permanent magnetic material for use in such application as television yokes, refrigerator door latches, mechanical couplings, and electrical motors and generators.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the spirit and scope of the invention, it is to be understood that the invention is not to be limited to said details except as set forth in the appended claims.

I claim:

1. As a composition of matter, the ferromagnetic ma- 11815131 BaMnFe O 2. As a composition of matter, the ferromagnetic material BaMnFe O with an intrinsic coercive force of about 3350 oersteds, remanence of 1425 gauss, a saturation magnetization of about 1580 gauss, and a resistivity of greater than 10 ohm-cm.

3. A process for producing a ferromagnetic material which comprises heating at a temperature of about 600 C. to 1000 F. for about /2 hour to 2 hours a powdered mixture of Fe O and BaMnO, in a mol ratio of 6:1, cooling the product thus obtained, grinding the product to a powder, compacting the powder into a unitary mass, and heating said mass at a temperature ranging between 1000 C. and 1300 C. for from 2-5 hours, and recovering a ferromagnetic material.

4. A process for producing a ferromagnetic material which comprises heating at a temperature of C. for /4 of an hour a powdered mixture of Fe O and BaMnO in a mol ratio of 6:1, cooling the product thus obtained, grinding the product to a powder, compacting the powder into a unitary mass, and heating said mass at a temperature of 1150 C. for 4 hours, and recovering a ferromagnetic material.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Erchak et al.: American Chemical Society Journal, vol. 68 (1945), pp. 2082-2093.

Ionker et al.: Physica XIX (1953), pp. -130.

Gorter: Proceedings of the I.R.E., vol. 43, No. 12 (1955), pp. 1945-73.

Claims

1. AS A COMPOSITION OF MATTER, THE FERROMAGNETIC MATERIAL BAMNFE12O21.