DEN0009926MA - - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

Registration date: December 17, 1954. Advertised on October 31, 1956

GERMAN PATENT OFFICE

Magnetic cores with an almost rectangular hysteresis loop are for various applications significant. This type of core is used, among other things, for so-called "magnetic storage" used (see, for example, W. N. Papian: "Proceedings of the I. R.E.", April 1952, pp. 475 to 478, and D. R. Brown and E. Albers-Schoenberg: "Electronics", April 1953, pp. 146 to 149). Such magnetic Memory is used e.g. B. in calculating machines and in self-driving pilots. Next will be this Cores used in magnetic switches.

The measure that indicates how close the shape of the hysteresis loop comes close to the rectangular shape

express yourself quantitatively in different ways.

A common scale is e.g. B. the quotient - ~ - .

B _c i

The meaning of this quotient is explained with reference to FIG. 1, which is a schematic representation of part of a saturation magnetization curve. In this figure, B _{denotes 1} . the remanent induction while B ₀₁ denotes the induction at which the hysteresis loop is just closing. In practice it is often not easy to measure B ₀₁ with great accuracy. However, it is easy to _{find an approximately correct value for B ol} by taking the mean value of the inductions after partial

609 660/369

N 9926 VIIIc / 21g

Magnetization or partial demagnetization (with intermittent saturation) is assumed, both inductions being measured at the same field strength, which is selected such that the inductions mentioned differ by more than 1%, but less than 3 ° / ₀ . The measurement results reported below were also determined according to this measurement principle. For the measurements was. a ballistic galvanometer is used (see Bozorth: ίο "Ferromagnetism", New York, 1951, p. 843). the

The quotient - ^ - was always measured on a ring-

shaped magnetic core with a constant cross-section of the ferromagnetic material along the the entire circumference of the ring and with an outer diameter that is a maximum of 1.6 times the inner diameter is equivalent to.

A ratio (R _s ) _max can also be specified as a measure of how close the shape of the hysteresis loop approximates the rectangular shape. For the significance of this variable, reference is made to the literature mentioned above. For the sake of completeness, a brief explanation follows with reference to FIG. 2, which is also a schematic representation of part of a magnetization curve which relates to a case in which the demagnetization was started before the magnetic saturation was reached. The size (R _s ) _max is defined as follows:

B ₁

(H _m )

The quotient

'(- ■ * Η «ι)

m)

is a function of the applied highest field strength.ffm. It turns out that this quotient has a maximum value for a certain value of H _m , which usually differs little from the coercive force H _0. This maximum value of the quotient is denoted by the symbol (R _s ) _max. The measurements of B _(Bm) and B (-iE _m ) required to determine (R ₃ ) max can again be performed using a ballistic

Galvanometers are carried out. As test objects for the determination of the following communicated In this case, too, the measurement results were used for ring-shaped magnetic cores with a constant cross-section the magnetic material along the entire circumference of the ring and with an outer diameter, which is a maximum of 1.6 times the inner diameter amounts to.

When using ferromagnetic materials with an almost rectangular hysteresis loop it is mostly a matter of alternating currents of high frequency, and so it should be eddy currents be suppressed as much as possible. When using ferromagnetic alloys, this can to a certain extent Extent can be achieved in that the magnetic core consists of mutually isolated, very thin layers of the ferromagnetic material is composed. However, it is often extremely difficult to get out of these thin layers of cores with an almost rectangular hysteresis loop. at At high frequencies, it is therefore advantageous or even necessary to use magnetically soft materials containing ferrioxide to use with spinel structure. In fact, these materials already have a very high inherent quality low electrical conductivity.

For the usability of the magnetic cores in question for magnetic memories and magnetic switches, an essential condition is that the coercive force (H _e ) should be low (expediently not higher than 10 Örsted, preferably even lower than 4 Örsted), otherwise the electromagnetic losses will increase are high.

According to the 'invention it has now been found that ferrite materials for magnetic cores, which have an almost rectangular hysteresis loop, can be obtained by using a mixture of copper, nickel and iron compounds in a gas atmosphere with an oxygen content of more than 50 percent by volume a temperature of 1375 to 1450 ⁰ C is heated, the proportions of copper, nickel and iron compounds are chosen so that a compound of the formula

Cu ₃₃ Ni (^ _x) Fe ₂ O ₄

arises, in which χ = ο, οΐ is up to 0.05.

Magnetic cores that consist of at least one connection produced using this process, meet the following conditions:

B ^ B _rl

> 0.7

{R _S ) max > .0.6

H _c <4 Örsted.

Such magnetic cores are therefore excellently suited for the purposes mentioned above.

Ferromagnetic ferrites of the general formula CUaNi ₁ ^ Fe ₂ O ₄ are known as ferromagnetic materials; However, it has not yet been recognized that it is possible through the use of a very low copper content and special manufacturing conditions, as described above, to approximate the hysteresis loop of ferrites of this composition of the rectangular shape and thus the use of these ferrites for magnetic storage u . Like. To enable.

example

A mixture of copper oxide CuO, nickel carbonate NiCO ₃ and iron oxide Fe ₂ O ₃ is ground in alcohol for 5 hours and then pre-sintered ^{at 900 ° C. in air for 1 hour.} After cooling, the reaction product is ground again in alcohol for 2 hours, after which the ground product is pressed into the shape of a ring. This ring is sintered in oxygen ^{at approximately 1400 ° C. for 2 hours.}

By changing the ratio between the amounts of copper oxide and nickel carbonate in the starting material can toroidal cores of different. Composition are made. From some of these

660/369

N 9926 VIIIc / 21g

The table below gives the composition, the value of the quotient ■ ---, the value of (R _s ) _max and the value of H _{0 for} magnetic cores.

composition B _r [■ Kslmax (inörsted) Cu _0i01 Ni ₀ . ₉₉ Fe ₂ O ₄
Cu _Oi O _{3 0} Ni, ₉₇ Fe ₂ 0 ₄
O ^Cu, 05 Ni _0, D ₂ O ₅ Fe ₁ Vol 0.65
0.70
0.70 3.2
3> o
2.8 0.70
0.78
0.70

Claims (2)

Patent claims: i. Process for the production of a ferrite material for magnetic cores, which have an almost rectangular hysteresis loop, characterized in that a mixture of copper, nickel and iron compounds in a gas atmosphere with an oxygen content of more than 50 percent by volume to a temperature of 1375 to 1450 ⁰ C is heated, the proportions of copper, nickel and iron compounds are chosen so that a compound of the formula arises in which χ - ο, οΐ is up to 0.05. 2. Magnetic core, characterized in that it consists of at least one by the method according to Claim 1 established connection exists. Considered publications: "AEG-Mitteüungen" ·, 41, 1951, pp. 135 to 142; "Physica", 1936, pp. 463 to 483. For this purpose ι sheet of drawings