DE1471300B2 - MAGNETIC STORAGE CORE BODY MADE OF A LITHIUM FERRITE AND THE PROCESS FOR PRODUCING IT - Google Patents

Description

The invention relates to a magnetic memory core body for a wide operating temperature range made of a burned lithium ferrite with metal oxide additives. The invention also relates to a method for the production of such a memory core body.

Storage core bodies made of ferrites with rectangular hysteresis loops are widely used as Storage elements of calculating machines application. There is often the task of the memory core body for a wide operating temperature range, e.g. B. from -60 to + 100 ° C, without special temperature compensation to use.

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

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

The use of lithium nickel ferrites and lithium copper ferrites is also known Memory cores. It turns out that with a lithium copper ferrite the signal output voltage after a certain excitation remains comparatively small, so that high excitation currents are necessary.

A lithium-magnesium ferrite with a magnesium oxide content of 28.6 mol percent is already known. The squareness ratio of this ferrite is 0.35 and achieved through a special treatment the value 0.55. This value is extremely bad for a storage core, even though it has a high magnesium oxide content is added.

Lithium ferrites, which have a high Curie temperature, are already known for high-frequency ferrites. However, no prediction can be made from the magnitude of the Curie temperature in the case of a high-frequency ferrite about the size of the Curie temperature of a rectangular lithium ferrite, because perfect for the same other additives are required.

Basically, when the Curie temperature of a ferrite of a storage core is high, the excitation current is generally high; d. that is, these two properties conflict with each other. It is therefore difficult to produce a core material that has a high Curie temperature and a low one at the same time Coercive force, a precise rectangular shape which is an indispensable feature of memory cores, and has a high density of lines of force in relation to the output voltage. So far it has not been possible to get one To produce core material that meets all of these conditions.

The object of the invention is to create a storage core body with the lowest possible excitation current while maintaining a wide operating temperature range. The reduction of the excitation current is a prerequisite for the use of solid-state circuit arrangements for the control stage of memory cores, since such solid-state transistors can only carry currents of up to about 1000 mA.
This task is supplemented by; from 1 to 10 mole percent magnesium oxide and from 0 to 10 mole percent zinc oxide dissolved to form a lithium ferrite.

Such a storage core body has an excitation current between about 700 and 1100 mA and is thus

ίο in an area suitable for practical use. Despite this comparatively low excitation current, which is also used in Mn-Mg-Zn ferrites, the Curie point is above 400 ^° C., so that a low temperature coefficient is obtained for a storage core body according to the invention. 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 can still be used in its entirety. However, it can be an essential Achieve reduction in the excitation current by increasing the Curie temperature, prompting it for use in connection with solid-state circuits mainly matters. Retains the squareness ratio its great value.

The invention will now be described on the basis of a few exemplary embodiments with reference to the drawings explained. It shows

F i g. 1 shows a timing diagram of a test pulse sequence for a memory core body,

F i g. 2 is a graph showing characteristics of a memory core body according to that given below Embodiment 1,

F i g. 3 shows a similar illustration of the characteristic curves of a storage core body according to exemplary embodiment 2;

F i g. 4 the temperature coefficient as a function of the excitation current,

F i g. 5 a comparison between temperature. coefficient and Curie temperature for Mn-Mg-Zn ferrites and with ferrites according to the invention and

F i g. 6 corresponding characteristic curves as in FIG. 2 for a lithium copper ferrite.

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

In particular, it has been found that by using a lithium ferrite as the base material and adding 1 to 10 mole percent magnesium oxide to it, it is possible to obtain a storage core material which has a high squareness ratio and which can also be operated over a wide temperature range. It has also been found that if an amount of zinc oxide within the range of 0 to 10 mole percent is added to this lithium-magnesium ferrite, it is possible to decrease the exciting current of the core material. In this case, however, the operating temperature range tends to be narrowed.
Of the lithium system ferrites, the lithium-nickel system and the lithium-copper system are already known and have also been considered for use as storage core materials for operation over a wide temperature range.

However, these ferrites meet the requirement of a rectangular shape. Furthermore, the sensitivity small. Furthermore, ferrites of the lithium-magnesium system are known. However, it became the addition of Zinc oxide to a lithium-magnesium system ferrite to reduce the excitation current according to the Invention never proposed so far.

For a better understanding of the invention, the following examples are given, of which the example 1 relates to an example of a storage core material according to the invention with a wide temperature range and Example 2 relates to the material of Example 1, which has a low excitation current characteristic has been given.

example 1

Lithium carbonate (Li ₂ CO ₃ ) and iron oxide (· Fe ₂ O ₃ ) were mixed in proportions at a molar ratio of 1: 5 for several hours in a ball mill (a power mortar can also be used). _{The obtained mixture was preburnt} at 1000 ° C. for 1 hour, then cooled and ground in a mortar, whereby a magnetic material having a composition of Li ₀₅ Fe 2f5 O _{4 was} obtained. Various amounts of magnesium oxide (MgO) samples of this Li _{0> 5} Fe _{2 (5} O _{4) were} added and mixed with these to obtain mixtures of the general formula

Li _{0) 5} Fe _2f5 O ₄ + X (mole percent) MgO

to obtain.

From these mixtures, granules were formed with a suitable binder, whereupon the Granulate rings were formed whose dimensions after firing were each 51 mm in thickness. The rings thus obtained were placed in a stream of oxygen gas at a temperature of 100 to 12C0 ° C for 10 hours burned. The oxygen gas was used because the rectangular shape is deteriorated if the rings of core material were fired in air.

The cores manufactured in this way were measured for their memory characteristics using a current pulse train as shown in FIG. 1 specified. 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 {Idjlm) of 0.5 and a “1” interference output voltage d V _{1 was} read for the pulse /, while an “O” interference output voltage d F _{0 was} read for the pulse S. In the following, the “!” Interference output voltage d F ₁ , the “O” interference output voltage dF _o and the switching time y ₅ at the point at which the “O” interference output voltage dF ₀ suddenly increases are used as core parameters.

The change in properties when the amount X (mol%) of the mentioned magnesium oxide (MgO) added is changed is shown in FIG. 2 specified. As can be seen from the curves shown in this, the "!" - interference output voltage d F ₁ for X = 0 is low and unsuitable, but OV ₁ 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 mole percent, AV ₁ decreases again, and at values of JSf higher than 10 mole percent, dF ₀ increases, so that the material becomes unusable.

The atomic ratio between lithium and iron in the composition Li _0f5 Fe _{2> 5} O ₄ + ZMgO of this example is 1: 5, but if there is a deviation from this ratio, the properties become poor. The Curie temperature of this Li-Mg system ferrite is higher than 500 ° C, and the change with the temperature of the disturbance-one output voltage OV ₁ and the excitation current I _m is 0.21 ° / o / ° C and 0, respectively. 17 ° / ₀ / ° C, which corresponds to improvements of one fifth to one sixth of conventional core materials. The prepared core material of this example is therefore operable in the operating range of -50 to +100 ⁰ C.

Example 2

The excitation current I _{m of} the core according to Example 1 is as in FIG. 1, between 1100 and 1200 mA, which is quite high. To reduce this current, zinc oxide (ZnO) was added to the aforementioned Li-Mg system ferrite. The procedure for making the cores was the same as that described for Example 1. The storage characteristic of the fired core material from the formula

Li _0, 5Fe _{2> 5} O ₄ + 1.7 mole percent Mg + X (mole percent), ZnO,

thus obtained was measured. The results of this measurement are shown in FIG. 3 shown.

As shown in FIG. 3, the excitation current I _m decreases, as expected, with the amount of ZnO added, but the "1" interference output voltage UV ₁ also decreases accordingly. The limit on the amount of ZnO added is 10 mole percent, and any further increase in the amount added deteriorates the rectangular shape, making the core unsuitable for use as a memory core.

The addition of ZnO has the further effect of lowering the Curie temperature, which becomes about 400 ° C. with an addition of ZnO of 10 mol percent. Accordingly, the operating temperature range of the core also becomes narrow. In the case of a core with 10 mol percent ZnO, the operating temperature range is approximately -10 to 6O ⁰ C.

F i g. 4 shows the temperature coefficient of I _m and AV ₁ . The values are based on measurements within the temperature range between 0 and 8O ⁰ C, with 20 ⁰ C as a reference. Even with an addition of 10 mol percent ZnO, the temperature coefficient of I _{1n is} only 0.34 ° / ₀ / ° C. Such a temperature coefficient is extremely low and therefore very favorable for practical use.

F i g. 5 shows the relationship between temperature coefficient and Curie temperature for Mn-Mg-Zn ferrites and for Li-Mg-Zn ferrites according to the invention. It can be seen that this ratio applies to the ferrites according to the invention is extremely favorable.

F i g. 6 shows characteristic curves of the variable AV ₁ , I _m and t _s for lithium-copper-ferrites as a function of the copper content. The respective measurements correspond to FIG. 2. It can be clearly seen that the values d V _{1 are} significantly below the values according to FIG. 2 stay.

Claims (3)

Patent claims: 1. Magnetic storage core body for a wide operating temperature range from a burned lithium _{ferrite (Li 0; 5} Fe 2r5 O ₄ ) with metal oxide additions, characterized by additions of 1 to 10 mol percent magnesium oxide (MgO) and 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 1100 to 1200 ⁰ C in a stream of oxygen. 3. The method according to claim 2, characterized in that that in addition to 1 to 10 mol percent magnesium oxide, 0 to 10 mol percent zinc oxide are also added to the starting mixture. 1 sheet of drawings