DE1471300A1 - Magnetic storage core made of a lithium ferrite and process for its production - Google Patents

Description

U71300

DR. ING. EHN8T MAIEK

PATENT ADVOCATE

8 MUNICH S2

A 3 ^ 764 November 19, 1968

EM / Has / MM

File number: P 14 71 3OO.9 (K 53 656 VIb / 80b

KABUSHIKI KAISHA HITACHI SEISAKUSHO,

4 _t 1-Chome, Marunouchi, Chiyoda-Ku, Tokyo-To / Japan

Magnetic storage core body made of a lithium ferrite and method for its production

The invention relates to a magnetic memory core body for a wide operating temperature range from a Burned lithium ferrite with metal oxide additives. The invention also relates to a method for producing a sol chen storage core body.

Storage core body made of perrites with rectangular

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Hysteresis loops are widely used as storage elements in computing machines. It exists in many ways the task of making the storage core body suitable for a wide operating temperature range, e.g. from -6O ° Celsius to + 100o Celsius, without using special temperature compensation.

When using ferrites of the Cu-Mn system or of the Mn-Mg system, which have hitherto been used largely as storage element materials are used are their operating ranges when used as storage devices for calculating machines usually limited to 0 to 60 ° Celsius even with temperature equalization. When these materials are at a temperature of about 60 ° Celsius or higher are used, they lose the rectangular shape of their characteristic and also are the temperature coefficients of the excitation currents are large. Such ferrites are therefore used for memory devices in calculating machines not functional.

In addition, Li-Mn-Al ferrites are known, where with increasing Lithium content the Curie temperature and thus also the Excitation current increase. Furthermore, a Mg-Zn ferrite is with a Lithium oxide addition known in addition to other oxide additives, its However, the Curie point is small and therefore unsuitable for operation over a wide temperature range.

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A lithium-magnesium ferrite with a magnesium oxide content of 28.6 mol percent is already known. That The squareness ratio of this ferrite is 0.55 and reaches a value of 0.55 through special treatment. This value is extremely bad for a memory core, although a high proportion of magnesium oxide is added.

Lithium ferrites are already known for high frequency ferrites, which have a high Curie temperature. From the size of the Curie temperature for a high-frequency ferrite but no prediction whatsoever about the size of the CU temperature a rectangular lithium ferrite because it requires completely different additives.

Basically, if the Curie temperature is one Ferrites of a storage core is high, the excitation current is generally high, i.e. these two properties come together in conflict. It is therefore difficult to manufacture a core material that simultaneously has a high Curie temperature, a low coercive force, a precise rectangular shape which is an indispensable feature of memory cores, and a high one Has the density of lines of force in relation to the output voltage. So far it has not been possible to produce a core material that all these conditions are avenged.

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The object of the invention is to create a storage core body with the lowest possible excitation current while maintaining it a wide operating temperature range. The reduction of the excitation current is a prerequisite for the application of pest body circuit arrangements for the control stages of memory cores, as solid-state transistors of this type can only carry currents up to approx. 1,000 mA.

This object is achieved by adding from 1 to 10 mole percent magnesium oxide and from 0 to 10 mole percent zinc oxide dissolved a lithium ferrite.

Such a storage core body has an excitation current between about 700 and 1,100 mA and is therefore in a for the practical use appropriate area. Despite this comparatively low excitation current, which is also the case with Mn-Mg-Zn perrites is used, the Curie point is above 400 ° Celsius, so that for a memory core body after the invention receives a low temperature coefficient. As a result, the operating temperature range is very wide.

However, one has to accept a certain deterioration in the interference ratio. This is permissible since the ferrite still remains fully usable. It

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however, a substantial reduction in the excitation current can be achieved by increasing the Curie temperature, whereupon it for use in conjunction with plague body circuits mainly matters. The squareness ratio retains its high value.

The invention will now be explained on the basis of a few exemplary embodiments with reference to the accompanying drawings. Show it:

1 shows a time diagram of a test pulse train for a storage core body,

Fig. 2 is a graph showing characteristics of a memory core body downward specified embodiment 1,

5 shows a similar representation of the characteristic curves a memory core body according to embodiment 2,

4 shows the temperature coefficient as a function of the excitation current and

Fig. 5 shows a comparison between temperature coefficient and Curie temperature for Mn-Mg-Zn ferrites and for ferrites according to the invention.

According to the invention, to produce a core material that can be operated over a wide temperature range, the property of lithium ferrite, which has a Curie temperature of about 600 ^° C. and also has a certain rectangular shape, is used.

In particular, it was found that the

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Turning this lithium Perrites as a base material and by adding 1-10 mole percent magnesium oxide to this it is possible to achieve a storage core material, which has a high squareness ratio and can also be operated over a wide temperature range. It was also found that if this is lithium-magnesium ferrite an amount of zinc oxide within the range of 0-10 mole percent is added, if possible, the excitation current of the core material. In this case, however, the operating temperature range tends to to get a little tighter.

Of the lithium system ferrites, the lithium-nickel system and the lithium-copper system are already known, but these ferrites have never been specifically considered for use as storage core materials for operation over a wide temperature range. In fact, you can * not say that these ferrites meet the requirement of rectangular shape. Furthermore, ferrites of the lithium-magnesium system are known. However, the addition of zinc oxide to a lithium magnesia system ferrite to reduce the excitation current according to the invention has never been proposed.

For a better understanding of the invention, the following examples are given, of which Example 1 is based

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an example of a memory core material according to the invention with a wide temperature range relates and the example 2 on the material of Example 1, which has a low excitation current characteristic has been given.

• Example 1

Lithium carbonate (Li ₂ CO ^) and ^ C - iron oxide (oC. Were mixed in proportions with a molar ratio of 1: 5 for several ύ hours in a ball mill (a powered mortar can also be used). The resulting mixture was stirred at 1000 ° Pre-burned C for one hour, then cooled and ground in a mortar, whereby a magnetic material with the composition LiQcFe ₂ , cO ^ was obtained. Various amounts of magnesium oxide (MgO) samples of this Li ₀ , cFe ₂ , j-Oij. Were added and mixed with these to form mixtures of the general formula

Li ₀ , t-Fe ₂ , 50 / j. + X (mole percent) MgO g

to obtain.

A granulate was formed from these mixtures with a suitable binding agent, after which rings were formed from the granulate whose dimensions after firing were 51 mm in each

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of the thick. The rings obtained in this way were ^{fired at a temperature of 1100 to 1200 °} C. for 10 hours in a stream of oxygen gas. The oxygen gas would be used because the rectangular shape would be compromised if the rings of core material were fired in air.

The cores produced in this way were measured for their memory characteristics using a current pulse train as in Pig. I stated. The pulse duration was 2.5 microseconds and the pulse rise time was 0.2 microseconds. Measurements were also carried out with an interference ratio (Id / Im) of 0.5 and a ^w 1 "interference output voltage dVl was read off for pulse J, while a ^w 0" interference output voltage dV _{o was} read off for pulse S. Subsequently, the "1" disturbance output voltage dV ^, the "0" disturbance output voltage dV _o and the switching time Vs ^{at the} point * at which the ⁿ 0 ^M disturbance output voltage dV _Q suddenly increases are used as characteristics of the core.

The change in properties when the amount X (mol%) of the mentioned magnesium oxide (MgO) added is changed is shown in FIG. As can be seen from the curves shown in this, the "1" disturbance output voltage dV ₁ for X = O is low and unsuitable, however

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dV _x suddenly increases at X = 1.0 and shows good properties. As a result, the rectangular shape has been improved.

When the added amount of MgO becomes larger than 2.0 mol percent, it decreases at values of X higher than 10 mol percent are, dV closed, so that the material becomes unusable.

The atomic ratio between lithium and iron is %

with the composition Lig, tjFe2,50i |. + XMgO of this example 1: 5, however, if there is any deviation from this ratio, the properties become poor. The Curie temperature of this Li-Mg system periteal is higher than 500 ⁰ C and the change with the temperature of the disturbance one output voltage UV ₁ and the excitation current I _m is 0.21 % / ° C or 0.17 # / ° C, which corresponds to improvements of 1/5 to 1/6 of conventional core materials. The core material produced according to this example is therefore in the operating range of -50 to |

+ LOCPC operational.

Example 2

The excitation current I _{n of} the core according to Example 1 is as in Pig. 1, between 1100 to 1200 mA, which is quite high. To reduce this current, zinc oxide ++ decreases dVj again, and

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(ZnO) added to the aforementioned Li-Mg system ferrite. That The procedure for making the cores was the same as that described in Example 1. The storage characteristics of the burned core material from the formula

1.7 mole percent Mg + X (mole percent)

ZnO,

thus obtained from these catfish was measured. The results of this measurement are shown in FIG.

As can be seen from Fig. 3, the excitation current increases As expected, Im decreases with the amount of ZnO added, but the "1" interference output voltage dVi also decreases accordingly away. The limit on the amount of ZnO added is 10 mole percent and has any further increase in the added Amount of approval of the rectangular shape Consequence, making the core unsuitable for use as a memory core.

The addition of ZnO has the further effect of lowering the Curie temperature, which is about 400 ° C. when it is added of ZnO becomes 10 mole percent. Accordingly, the operating temperature range of the core is also narrow. At a Core with 10 mole percent ZnO is the operating temperature range around -10 to 60OC.

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Figure 4 shows the temperature coefficient of In and DVI · The values are based on measurements within the temperature range between ⁰ ° C and 80 ° C, with 20 ⁰ C as a reference. Even with an addition of 10 mol percent ZnO, the temperature coefficient of Im is only 0.54 % / ° C. Such a temperature coefficient is extremely low and therefore very favorable for practical use.

Figure 5 shows the relationship between temperature coefficient and Curie temperature for Mn-Mg-Zn-Perrite and for Li-Mg-Zn ferrites according to the invention. You can see that this Ratio for the ferrites according to the invention is extremely favorable.

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Claims (1)

Η7Ί300 (NEW) PATENT CLAIMS 1. Magnetic storage core body for a wide operating temperature range made of a burned lithium ferrite (LiQjCjFe ₂ XrO ^) with metal oxide additives, characterized by additives of 1 to 10 mol percent magnesium oxide (MgO) and from 0 to 10 mol percent zinc oxide (ZnO). 2. A method for producing a memory core body according to claim 1, characterized in that between 1 and 10 mol percent magnesium oxide and lithium ferrite as the remainder are mixed, the mixture obtained is formed into granules by using a binder, the granules are brought into the geometric shape of a memory core and the shaped core is fired at a temperature in the range from 1,100 to 1200 ^° C. in a stream of oxygen. 5. The method according to claim 2, characterized in that In addition to 1 to 10 mol percent magnesium oxide, 0 to 10 mol percent zinc oxide can also be added to the starting mixture. • * 8Ue documents, v · 7 *:. \ .- s ..; No. ι Sau 3 de 00983 W13 2 Blank page