DE1471340C - Process for the production of a magnetic core with an almost rectangular hysteresis loop - Google Patents

Description

The invention relates to a method for producing a magnetic core with an almost rectangular hysteresis loop and low temperature dependence of the one signal and the peak time from a ferromagnetic mixed ferrite material, in which a pre-sintered mass of oxides of lithium, manganese, iron and optionally nickel, pressed into the desired shape , and / or of compounds of these metals, which are sintered into these oxides on strong heating, the relative amounts of the aforementioned metals in the sintered mass, expressed in mole percent of the oxides Li, O, MnO, Fe ₂ O ₃ and NiO ,

2.5 to 16.4 mole percent Li ₂ O,

0.3 to 68 mole percent MnO,

32 to 82 mole percent Fe ₂ O ₃ and

0 to 14 mole percent NiO

be. Such magnetic cores are z. B. in electronic calculating machines as storage elements used.

The suitability of magnetic cores with rectangular hysteresis loops as storage elements is determined by their current pulse characteristics, ie by their behavior under current pulse ratios. Important in this context is z. B. the occurrence of a clear difference between the "zero signal" and the "one signal" (in computing machine technology a distinction is made between the "undisturbed" one signal uV \ and the "disturbed" one signal rV \\ in one good storage element, however, these sizes are only slightly different from one another). In addition to a sufficiently large "squareness" of the hysteresis loop, for a given rise time of the control current, the time course between the start of the control current pulse and the point in time at which the output voltage of the one signal reaches its maximum value is almost constant. For practical reasons, it is preferable not to start from the start of the control current pulse, but rather from the point in time at which the control current reaches a strength of 10% of its maximum value. The "peak time" (T _p ) of a magnetic core is the time course between the point in time at which the control current reaches a level of 10% of its maximum value and the point in time at which the output voltage of the one-signal generated by the relevant control current pulse is at its maximum has become. This peak time naturally depends on the rise time (r _r ) of the control current pulse. In the studies that led to the present invention, the rise time was always 0.15 microseconds.

So far, one has the changes in the current pulse characteristics that occur due to temperature changes of storage elements mostly corrected by changing the control current. You also have that whole system of storage elements placed in a thermostat to avoid disruptive temperature changes to avoid. However, these procedures are involved and cumbersome. In addition, they are unusable, if temperature differences occur between the individual storage elements during the operation of the system, because one element is switched more often than another in a certain period of time. It is therefore of great importance to be able to have storage elements that are not just a sufficiently large Have the square wave ratio of the hysteresis loop, but also where the output voltage of the One signal as well as the peak time within a wide temperature range (preferably between - 40 and + 125 ° C) not at all or only to a small extent depend on the temperature.

Magnetic cores with an almost rectangular hysteresis loop made of lithium manganese ferrites are

ίο already known. But they were manufactured by sintering at a temperature up to 1200 ^0C. It was previously believed that the volatility of lithium oxide stood in the way of using sintering temperatures higher than 1200 ° C. The magnetic cores produced in this way, however, have either a relatively small one signal and / or a considerable temperature dependence of the one signal and the peak time.

The invention is based on the object of a method for producing magnetic cores with rectangular hysteresis loop made of lithium manganese (nickel) ferrite indicating a low temperature dependence of the one signal and the peak time.

This is achieved in a method of the type mentioned at the beginning according to the invention in that the pre-sintering takes place at a temperature below 800 ^° C. and the sintering takes place at a temperature between 1200 and 1400 ^° C. in dry air or in a dry air-oxygen mixture.

It was found that volatilization of the lithium oxide occurs at sintering temperatures above 1200 ° C can be avoided if it is ensured that the sintering takes place in a gas atmosphere that does not or at least contains almost no water vapor. Comparing the manufactured according to the invention Magnetic cores with regard to their suitability for use as memory cores with known ones made of manganese - Magnesium (zinc) ferrites, manganese - copper (zinc) ferrites or existing lithium manganese ferrites Magnetic cores, the following results: With higher manganese contents, the differ Magnetic cores manufactured according to the invention in the rest of the known with the just mentioned Magnetic cores have equivalent properties due to a noticeably high value of the output voltage of the one signal. In the case of lower manganese contents, equivalence with the relevant one occurs in the case of the rest known magnetic cores, as favorable properties a very low temperature coefficient the output voltage of the one signal and a very low temperature coefficient of the peak time on.

The most favorable results are achieved if the mass sintered by heating to a temperature between 1200 and 1400 ⁰ C is first cooled at a rate of at most 30 ⁰ C per minute to a ^{temperature 100 to 600 0} C lower and then quenched or if the by heating to a temperature between 1200 and 1400 ⁰ C sintered mass is cooled at a rate of more than 30 ⁰ C per minute to a ^{temperature 100 to 600 0} C lower, the mass is held at this lower temperature for at least 5 minutes and then quenched will.

An example illustrative of the invention now follows.

Together
Li ₂ O net case
the C
MnO ig in MoI
Dxyde
Fe ₂ O ₃ percent
NOK In front-
sintered
tempe-
rature
( ⁰ C) 14.2 4.9 74.6 6.3 750 Ifi. 35 3.92 79.73 - 750 8.7 26.1 65.2 - 750 5.0 50.0 45.0 - 700 14.2 4.9 74.6 6.3 550 12.4 7.45 73.95 6.2 750 12.4 1.24 73.96 12.4 750

Way of sintering and cooling

Output voltage
of the zero signal
(MV)

Output voltage
of the disturbed
One signal
rV \ (mV)

Peak time

(Microseconds)

Temperature coefficient of the peak time T _p

% per ° C

in the temperature range

Temperature coefficient of the undisturbed one signal uV

% per ⁰ C

in the temperature range

Heated to a peak temperature of 132O ° C in 60 seconds, Maintained at this temperature for 7 minutes, then cooled to 98O ° C in less than 3 minutes, Maintained at this temperature for 16 hours, finally quenched in air.

Heated in 60 seconds at the tips of temperature of 134O ⁰ C, held for 5 minutes at this temperature, cooled in an off oven to 1000 ⁰ C, quenched in air.

Heated to a peak temperature of 1265 ° C in 60 seconds, Maintained at this temperature for 5 minutes, cooled down to 1000 ° C in a switched-off oven, finally quenched in air.

Heated in 60 seconds on peak temperature of 126o ⁰ C, held for 5 minutes at this temperature, cooled in the stove off to 1000 ° C, quenched in air.

Heated in 45 seconds at the tips of temperature of 1350 ° C, held for 10 minutes at this temperature, cooled in an off oven to 95O ⁰ C, quenched in air.

Heated to a peak temperature of 128O ⁰ C in 60 seconds, kept at this temperature for 5 minutes, then ^{cooled to 980 0} C in less than 3 minutes, kept at this temperature for 20 minutes, finally quenched in the air.

Heated in 60 seconds on peak temperature of 1340 ° C, held at this temperature for 5 minutes, then cooled in less than 3 minutes at 1000 ⁰ C, 20 minutes held at that temperature long, quenched in the air.

17th

76

0.40

from -40 "C to +125 ⁰ C

19th

26th

18.5

5.5

16

78

164

120

35

96

0.38

0.25

0.34

0.34

0.38

from +20 ⁰ C to +80 ⁰ C

from + 2O ⁰ C to +80 ⁰ C

from +20 ⁰ C to + 80 ° C

from + O ⁰ C to ■ + 8O ⁰ C

from + 2O ⁰ C to + 8O ⁰ C

20th

60

0.32

from + 2O ⁰ C to +80 ⁰ C

0.5

from -40 ⁰ C to +125 ⁰ C

0.43

0.58

0.61

0.5

0.45

from ... to

+ 2O ⁰ C +80 ⁰ C

from +20 ⁰ C to +80 ⁰ C

from + 2O ⁰ C 45N until + 8O = C O from + O ⁰ C until + 80 ⁰ C

from + 2O ⁰ C to +80 ⁰ C

0.45

from ... to

+ 2O ⁰ C +80 ⁰ C

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example

Mixtures of lithium carbonate Li ₂ CO ₃ , manganese carbonate MnCO ₃ , iron oxide Fe ₂ O ₃ and optionally nickel carbonate NiCO ₃ were ground for 4 hours in ethanol in a ball mill. The mill products were presintered in air, cooled to room temperature and ball milled in ethanol for 16 hours. The ground products obtained in this way were granulated after the addition of an organic binder and pressed into rings ^{under a pressure of 1.5 t / cm 2.} These rings were sintered by heating at a temperature between 1200 and 1400 ^° C. in dry air.

In the table above, more details about the chemical composition and the manufacturing process of the magnetic cores as well as a number of measurement results are given. The measurements were all carried out at 25 ° C. As mentioned earlier, the rise time (T _1. ) Of the control current pulse was always 0.15 microseconds and the interference ratio was 0.61.

All of the cores of Samples 1 to 4 and 6 to 9 had an outer diameter of 1.3 mm, one Inner diameter of 0.8 mm and a height of 0.4 mm. For core # 5, these dimensions were 0.8 or 0.5 or 0.2 mm.

Claims (5)

Patent claims: 1. Process for the production of a magnetic core with an almost rectangular hysteresis loop and low temperature dependence of the one signal and the peak time from a ferromagnetic mixed ferrite material, in which a pre-sintered mass of oxides of lithium, manganese, iron and possibly nickel, and pressed into the desired shape / or of compounds of these metals, which pass into these oxides when heated, the relative amounts of the aforementioned metals in the sintered mass, expressed in mol percent of the oxides Li ₂ O, MnO, Fe ₂ O ₃ and NiO, 2.5 to 16.4 mole percent Li ₂ O, 0.3 to 68 mole percent MnO, 32 to 82 mole percent Fe ₂ O ₃ and 0 to 14 mole percent NiO be, characterized in that the pre-sintering takes place at a temperature below 800 ⁰ C and the sintering at a temperature between 1200 and 1400 ⁰ C in dry air or in a dry mixture of air and oxygen. 2. The method according to claim 1, characterized in that the ^{mass sintered by heating to a temperature between 1200 and 1400 0} C is initially cooled to a temperature of 100 to 600 ° C lower at a rate of at most 30 ^{0 C per minute and then quenched} will. 3. The method according to claim 1, characterized in that the by heating to a Temperature between 1200 and 1400 ⁰ C sintered mass is cooled at a rate of more than 30 ⁰ C per minute to a 100 to 600 ° C lower temperature, held at this lower temperature for at least 5 minutes and then quenched. 4. Magnetic core, which is manufactured according to one of claims 1 to 3. 5. Magnetic storage element, which consists of a .Magnetkern according to claim 4 in the form of a Ring with an outer diameter of 4 mm or less. 109527/273