DE1236575B - Magnetic layer storage - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

GlIc

German class: 21 al -37/06

Number: 1236575

File number: J 26582IX c / 21 al

Filing date: September 22, 1964

Open date: March 16, 1967

The invention relates to magnetic layer memories having a magnetic easy axis Thin-film memory cells for storing binary information, with the memory cells adjacent, orthogonally running bit and word drive lines, of which the word drive lines run parallel to the preferred axis and receive interrogation pulses when information is extracted, a magnetic field for an information-destroying deflection of the magnetization of a memory cell Generate transversely to the easy axis, with read lines, depending on such Deflection of the magnetization of a memory cell read pulses are induced with one of the Memory cells adjacent yoke made of soft magnetic material, which reduces the leakage flux of the memory cells partially takes up, and with means for rewriting read information.

In a word-organized magnetic layer memory, the word drive amplifiers are at the beginning of each Memory operation used to reduce the magnetization of the word line coupled to the associated word line To switch memory cells coherently in the hard direction. For writing binary information the bit drive amplifiers are then used in the memory cells of a selected word magnetic field components effective on the word drive pulse in the direction of the easy axis to generate, whereby after termination of the word drive pulse the rest position of the magnetization in the preferred direction in the memory cells coupled to the bit line corresponding to that to be written Information is determined. A word driver field is used to read out the stored information applied, and the polarity of the voltage of the by switching the magnetization into the hard direction of the read signal induced in each bit read line enables the idle position to be recognized, which the magnetization in the memory cells of the word had previously taken. Such storage arrangements therefore delete the previously stored information during the reading process.

In order to be able to meet all requirements as far as possible, memory arrangements should be compact in structure They should have a large storage capacity and a short one with little technical effort Allow access time, and they should also be able to read the information non-destructively. Around To achieve a high storage capacity, the individual memory element or the individual memory cell must be very small; it is, however, the case that the achievable read signal is the smaller, the smaller the Magnetic layer storage

Applicant:

International Business Machines Corporation,

Armonk, N. Y. (V. St. A.)

Representative:

Dipl.-Ing. H. E. Böhmer, patent attorney,

Boeblingen, Sindelfinger Str. 49

Named as inventor:

Dr. Wilhelm Jutzi, Adliswil;

Dr. Gerhard Kohn, Thalwil (Switzerland)

Claimed priority:

Switzerland of September 27, 1963 (11 943)

Memory cell is. Therefore, the effort required for sense amplifiers in the output circuits is considerable. In order to obtain sufficient read signals, the word driving field must have the anisotropy field strength of the Exceed the layer element. Such driving fields cause ■ - · together with in the direction of the light Axis acting field components - the unidirectional and coherent rotation switching of the magnetization simultaneously in all areas of the thin layer elements. This only the thin layers peculiar switching process is much faster than the so-called wall switching, in which one Domain only takes on the new state of magnetization one after the other.

The word driving field causes a complete rotation of the magnetization in the hard direction or by 90 °, based on the easy axis direction. If nothing else happens, then splinters the magnetization of the memory cells into many individual ones after such a word driving field has ceased

709 519/376

Domains, some of which are oriented in the one possible rest position of the easy direction, while the rest takes the other opposite rest position. But that is the binary informational value no longer detectable. Therefore, it is necessary that after the rotation switching of the magnetization of the memory cells in the hard direction field components are effective, which the in the drive slightly falling back magnetization in the entire layer into a certain rest position, thus avoiding the splintering of the layer into individual oppositely magnetized domains will.

In order to enable non-destructive reading, it is known in magnetic layer memories (USA patent specification 3 092 812) to use a word driving field, which the magnetization of the thin film elements does not deflect completely in the hard direction, so that after the word-driving field has ceased, the Magnetization clearly returns to the originally assumed rest position. This can be z. By using weaker word driving fields than those used in destructive reading will achieve.

It is also known (US Pat. No. 3,077,586) to apply this method to memory cells from each of which consists of a number of superimposed thin layers moving from layer to Layer alternately have a high and a low coercive force.

The amplitude of the read pulses that can be achieved in this way is, however, due to the smaller deflection of the magnetization much smaller than the amplitude of those read pulses that were received when interrogated a word-driving field full of strength. Especially when storing larger capacity, where the read pulses are to be sifted out of interference pulses, the amplitude of which is partly greater than that of the transmitted destructive extraction is obtained, requires a reliable evaluation of the non-destructive Removal of the smaller read pulses obtained results in a considerable increase in the circuit complexity. Another disadvantage is that In this operating mode, different amplitudes for the word drive field when writing and reading are required and that the extent of these amplitude differences must be adhered to very precisely. This also increases the circuit complexity.

It is also known (US Pat. No. 3,015,807) for the purpose of non-destructive extraction of information from magnetic layer storage devices, two superimposed magnetic layers for each storage element Provide different coercive force, one of which as a storage layer and the other is used as a reading layer. The easy axis of the storage layer is perpendicular to Easy axis of the reading layer arranged so that the storage layer, which by its higher coercive force remains unaffected by the interrogation pulses, a transverse field for the reading layer is generated, which ever according to the information content, the query field is supported or opposed to it. Another embodiment (Journal of Applied Physics, Supplement to Volume 30, No. 4, April 1959, pp. 54S, 55S) Such a double-layer memory cell provides that the easy axis of the memory layer runs parallel to the easy axis of the reading layer.

The storage layer, which is not affected by the interrogation pulses because of its higher coercive force is reversed, generates a bias field in the storage direction in the reading layer which returns the read layer to its starting position after the interrogation pulse has ended will. The disadvantage of these arrangements is that they differ due to the coercive force required between the storage and reading layers, high demands are placed on the properties of the magnetic layers place. Another disadvantage is that here, too, a distinction is made in the feed of the word drive pulses is necessary for the write and read memory operations. Standardized Word impulses that are used both for writing in and for querying information, cannot be used with these arrangements, otherwise they will not be used when interrogating only the read layer but also the memory layer would be switched.

It is also in the case of magnetic layer memories, which only allow information-destroying reading known to provide a yoke made of soft magnetic material adjacent to the magnetic layer memory cells, by which part of the by the remanent magnetization state of the memory cells caused leakage flux is absorbed (USA.-Patent 3 030 612). This achieves that the harmful, free leakage fluxes of the memory cells of a matrix are reduced.

The object of the present invention is, in a magnetic layer memory of the type just explained To provide measures through which a non-destructive extraction of information without significant Additional effort and avoidance of the disadvantages mentioned above of a non-destructive Known magnetic layer memory permitting information extraction is made possible.

In the case of a magnetic layer memory with thin-layer memory cells having a magnetic easy axis for storing binary information, orthogonally extending with adjacent memory cells Bit and word drive lines, of which the word drive lines are parallel to the easy axis run and received interrogation pulses supplied with an information extraction, which a magnetic field for an information-destroying deflection of the magnetization of a memory cell perpendicular to the easy axis generate, with read lines, in which depending on such a deflection of the Magnetization of a memory cell, read pulses are induced with one of the memory cells neighboring Yoke made of soft magnetic material that partially absorbs the leakage flux of the storage cells, and with means for rewriting read information, the Invention in that the material of the soft magnetic yoke has a relaxation time for changes of the magnetic state, which is in the order of magnitude of the duration of the interrogation pulses is, and that the duration of an interrogation pulse with respect to the relaxation time of the yoke material so it is coordinated that the magnetic field is still present in the yoke when the interrogation pulse dies away Residual magnetization following the removal of information, a reset of the memory cell in the magnetization state that was present before the start of the interrogation pulse.

Since the coherent rotary switching processes in the layers take place exceptionally quickly, so that the limit for the operating speed of the memory is not by the memory cells, but by the switching and regeneration time of the driver amplifier stages as well as the length of the drive lines is set, there is also no noteworthy value for rewriting taking place according to the invention additional time required.

There is already an older proposal according to which the switching operations of the magnetic layers in Eddy currents occurring in adjacent electrical conductors for rewriting a removed one Information can be exploited by the magnetic field generated by the eddy currents on the Acts memory cells and these after termination of the interrogation pulse in the magnetization state switches back that they took before the start of the interrogation pulse.

According to an advantageous development of the present invention, the adjacent ones in the memory cell can Eddy currents occurring in conductor parts and those in one of the magnetic layer adjacent soft magnetic yoke existing residual magnetization together to rewrite the extracted information can be exploited.

Further advantageous developments of the invention can be seen from the subclaims. At The invention is explained in more detail using the exemplary embodiments shown in the drawings. It shows

Fig. 1 is a schematic representation of a known Magnetic layer storage,

F i g. 2 is a perspective view on a greatly enlarged scale Scale of a part of the known magnetic memory comprising only one memory cell according to Fig. 1,

F i g. 3 shows a view of the end face of a memory cell and magnetic arranged above it Material with the field course of the word driving field shortly after switching the magnetization into the hard direction,

Fig. 4a and 4b the time-dependent course of the with a sudden change in a magnetic field associated induction inside magnetic material,

F i g. 5 a is a side view of a memory cell and magnetic arranged above it Material with the field course of the static bit field, if a binary information value is stored in the cell is,

5b shows a side view of a memory cell with the field profile of the bit field during the non-destructive reading process when the magnetization of the cell is switched in the hard direction, but the outer bit field is essentially because of the finite relaxation time of the magnetic material has been preserved,

6a and 6b show the time-dependent course of the induction linked to the bit field in the magnetic field Material during the non-destructive reading process as well as the associated word drive pulse,

F i g. 7 a is a side view of a memory cell and a magnetic device arranged below it Material as well as an intermediate conductive metal layer, with the field profile of the static Bit field, if a binary information value is stored in the cell,

F i g. 7 b shows a side view of a memory cell with the field profile of the bit field during the non-destructive operation Reading process when the magnetization of the cell is switched in the hard direction, the external bit field, however, essentially during the finite relaxation time of the magnetic material and the eddy currents generated in the conductive metal layer is retained.

1 and 2, the arrangement of a magnetic memory is shown schematically, from which the invention is based. The F i g. 1 indicates in plan the arrangement of the memory cells, drive lines and external circuits of the magnetic layer memory, while FIGS. Figure 2 is a perspective view of a greatly enlarged portion of a portion of the layered magnetic memory of Figure 1 which includes only a single memory cell. An insulating layer 12, on which the memory cells 14 are located, is applied to a metallic base plate 10. The memory cells 14 consist of umaxial anisotropic thin magnetic layers and are arranged in a matrix of bit lines and word columns. Each memory cell 14 is made of ferromagnetic material, such as. B. from an alloy of 80% nickel and 20% iron, and has a layer thickness of about 500 to 2000 A. The memory cells 14 can be produced by any of the known methods, such as. B. by vacuum evaporation, cathode sputtering, chemical precipitation or electrolytic precipitation on the metallic base plate 10. During the manufacturing process, the thin layer is exposed to a magnetic field that impresses it with the unaxial anisotropy. This defines an easy axis of the direction of remanent magnetic flux shown in FIG. 2 is indicated by the double arrow E. The memory cells 14 can be round, oval, square, or rectangular in shape; the shape shown here is rectangular with the easy axis E of each memory cell parallel to the longer edge. The length of each memory cell 14 is approximately 0.5 to 1 mm, while the width is approximately 0.3 mm.

The matrix of the memory cells 14 arranged in rows and columns can be in various ways getting produced. For example, during the manufacturing process in a vacuum through a mask Vaporized, whereby the particles are only in certain places and in a special arrangement

be knocked down through the openings in the mask. Another method can be metallic alloy by any of the aforementioned manufacturing processes in one complete coherent layer are deposited, and then the undesirable Parts of this coherent layer, i.e. H. the spaces between the memory cells, too eliminate e.g. B. by a photo etching process.

The base plate 10 is made of an electrically conductive material such as silver and on the surface, which carries the insulating layer 12, polished well. The insulating layer 12 consists, for. B. from a thin Layer of vapor-deposited silicon monoxide (SiO), which not only removes the memory cells 14 from the base plate 10 isolated, but also compensates for remaining surface roughness of the base plate 10. Even the adhesion properties are improved by such intermediate layers.

A number of bit lines B ₁ to B ₅ running in the row direction are provided, each of which is coupled to all memory cells 14 in a corresponding row of the memory matrix. The bit lines extend across the direction of the light armpit? of the magnetic layer memory cells. One end of each bit line B is conductively connected to the base plate 10 and the other end leads via a device 18 to an arrangement 16 which contains means for bit control and bit drive amplifiers. The devices 18.1 to 18.5 in each bit line B ₁ to B ₅ serve to enable each bit line to be used both for writing information and for reading it out. While information is being written in, the bit lines B are switched through to the bit drive amplifiers in the arrangement 16. For reading purposes, the bit drive amplifiers are disconnected and the sense amplifiers present in the devices 18 are connected to the respective bit line B. The bit lines B can have been produced by a vapor deposition process. They are electrically insulated from the memory cells 14 by a thin layer 22. The lines are suitably strip lines made in any of the known ways. They can also be slotted so that each drive line consists of several narrow strip lines connected in parallel.

A number of word lines W _x to W ₆ are provided in the memory matrix in the column direction. These word lines are also expediently strip lines which are produced by any known method. You can e.g. B. like the intermediate insulating layer 24 can be produced using masks by a vapor deposition process in a vacuum. It is also possible to etch the pattern of the lines out of a cohesive metal layer. This metal layer can also be applied to a surface or side of a thin insulating film. The word lines W run in the direction of the easy axis E of the memory cells 14, orthogonal to the bit lines B. Each word line W is coupled to the memory cells 14 of a word arranged in a column of the memory matrix. One end of each word line W is conductively connected to the base plate 10, while the other end is led to an arrangement 20 which contains the means for word control and the word drive amplifiers. A control device 21 is connected both to the arrangement 16 for bit control and to the arrangement 20 for word control. It is used to control the timing of the pulse sequences required for memory operations in accordance with the requirements of the computer system.

The devices 18 are used to connect the bit lines B during the part of the memory cycle which is used for writing information to the bit drive devices and the bit drive amplifiers in the arrangement 16, and to connect them during the part of the memory cycle which is to read the information is used to connect to the appropriate sense amplifier. In this way, the bit lines B serve the dual function of being the bit drive line during the write cycle and the read line during the read cycle. The devices 18 can be omitted if further lines are provided in the direction of the bit lines which are only used as read lines. The bit lines B can also be produced from a plurality of strip lines running in parallel. The longitudinal slots serve to allow the word driving field to penetrate better to the memory cells 14 and to avoid eddy currents in the lines.

A current pulse sent through a word line W uses its magnetic field to switch the magnetization of the coupled memory cells 14 in the hard direction. In order to be able to fulfill this function as well as possible, the word lines W must run as precisely as possible in the direction of the easy axis of the magnetization of the magnetic layer memory cells 14. You are free to choose the direction of the bit lines B; however, an arrangement orthogonal to the word lines has proven to be expedient. Because the bit lines B are also used as read lines during the read cycle, the best decoupling between these two line systems is achieved through the arrangement orthogonal to the word drive lines.

It is the task of the word lines W to switch the magnetization of the memory cells 14 of the selected word in the hard direction, while the task of the bit lines B is to provide field components acting in the direction of the easy axis so that the magnetization switched in the hard direction is in a predetermined rest position can fall back. The polarity of the bit drive pulses therefore depends on the information to be stored. The driving fields provided by the bit driving pulses are much weaker than the word driving fields. You can therefore only act on the magnetization of the memory cells that have been switched in the hard direction by a word driving field. The information contained in the memory cells of the words not activated remains undisturbed.

The usual working cycle in a word-organized memory arrangement is therefore as follows. For writing, a drive pulse in the word line of a selected word uses the Magnetization of the relevant memory cells switched in the hard direction at the same time. Nearly at the same time, but a little later, the bit lines lead depending on the binary information to be stored polarized write pulses, the field of which is the restoring torques after the word drive pulse has decayed for the unambiguous rotation switching of the magnetization of the relevant memory cells in supplies the predetermined rest position (0 or 1). For reading the binary digits in the memory cells of information stored in a word, a drive pulse in the word line is necessary in each Storage cell of this word simultaneously switches the magnetization in the hard direction. Depending on the Previously assumed rest position (0 or 1) occurs in every read line belonging to a binary digit a corresponding signal that is evaluated as a binary 0 or 1.

Memory of the type described so far are known.

The stored information is destroyed by the reading process, since it is not present external field components driving back the return of the magnetization of the memory cells in the rest position is not clearly determined. One of the

Possibilities for completing the read operation are that after the Word drive pulse in all memory cells of the read word converts the magnetization into a common predetermined rest position, e.g. B. the zero position switched will. For this purpose, a magnetic bias is required, which is created by the magnetic field of permanent magnets or electromagnets, or by the magnetic field of a continuous current or Current pulse can be delivered in the bit lines. Should, however, the read information content of the word are retained in the memory arrangement, the memory is normally regenerated usual by rewriting the information that has just been read out.

According to the invention, however, the magnetic induction in the magnetic layer storage cells is used as the energy store neighboring magnetic material exploited the paths of the relatively slower After the word-driving field has ceased, there is still a magnetic field in the vicinity of the Maintains magnetic layer memory cells, which acts back on the magnetization of the memory cells. According to the invention, this reaction is used to regenerate the originally stored information exploited. The word drive pulses only need to be short enough, shorter than the relaxation time of the in the easy direction of the magnetic field in the vicinity of the magnetic layer memory cells.

In Fig. 3 schematically shows a magnetic layer memory cell 14 in the presence of a word drive current i _w . The direction of the easy axis of magnetization corresponds to the direction of the word current i _w perpendicular to the plane of the paper. To make it easier to see, only the elements that are essential for the desired effect are drawn. The insulation and fastening means required in the practical implementation, as well as further strip lines required per se for the operation of the magnetic layer memory, are omitted in the figure to simplify the illustration. The magnetic layer memory cell 14, seen from the front edge, is located on the conductive metallic base plate 10. Above the magnetic layer memory cell 14, the word line W, which is divided into four parallel striplines by longitudinal slots, runs towards the viewer. As the registered field profile shows, the lines of force are essentially closed by the magnetic material 30, which acts like a yoke closing the magnetic circuit for the word driving fields. In this way, driving power is saved; because in order to make the usable field H _P in the interior of the memory cell 14 effective, the surroundings must also be magnetized. The air gaps are only present on both sides compared to the earlier open design of a magnetic layer storage system and are negligibly small. The relatively long path of the field H _M outside the magnetic layer memory cell 14 now runs for the most part in a magnetic material, that is to say in an environment with a significantly higher permeability than air. It should be at least ten times greater in amount.

A suitable magnetic material is, for example, ferrite. It can be in the form of ferrite plates be applied, or finely divided ferrite or ferrite powder is embedded in a suitable binder and covers the arrangement of the memory cells 14 of the magnetic memory in one layer. Farther carbonyl iron or HF iron can be used for this. It can also be a vapor-deposited ferromagnetic Layer can be used for this purpose. Since the magnetic material is soft magnetic the evaporated thin magnetic layers can also be isotropic, i.e. H. you do not need any

ίο to have preferred direction of easier magnetizability. However, anisotropic magnetic layers with the preferred direction are also parallel or perpendicular applicable to the easy direction of the magnetic layer memory cells. There are magnetic materials which has an inherent relaxation time with a time constant on the order of 5 to 20 nanoseconds have, and therefore according to the invention to provide a virtual bit field to enable the non-destructive reading can be exploited.

In Fig. 4 shows the time-dependent course of the induction B _M (t) in the magnetic material to explain this property, as it occurs in response to a sudden change in the associated magnetic field H _M (t)

z5 takes place. It is assumed that the magnetic field H _M suddenly changes from zero to a value _{Ή Μ} and shortly thereafter again assumes the value zero. The induction B _M can only follow this rectangular pulse of the magnetic field H _M at a slower speed. The rising and falling edges of the pulse of the field H _M, which are assumed to be ideally perpendicular, are transformed into edges running approximately according to an exponential function during the induction B _M which then occurs within the magnetic material. The same time constant T for rise and fall is in the order of magnitude of a few nanoseconds.

In Fig. 5a, a memory cell 14 is shown schematically in the case of the static field, ie in the rest position of the magnetization. The direction of the easy axis of magnetization corresponds to the arrows 2? /? for the magnetic induction within the memory cell 14 and H _P for the associated magnetic field. The memory cell 14, seen from the longitudinal edge, is located on the metallic base plate 10. A bit line B consisting of four striplines runs above the memory cell 14 perpendicular to the plane of the paper. The soft magnetic material is located above this

30. As can be seen from the field curve shown, the lines of force close essentially over the magnetic material 30, as indicated by the arrows and the designations H _M for the magnetic field in the magnetic material and B _M for the induction. The field also penetrates into the metallic base plate 10, but is much less dense there. The field component H _A acts in the airspace . As shown by the arrow labeled B _F and pointing to the left in the memory cell 14, the remanent magnetization of the magnetic layer is in one of the two rest positions in the direction of the easy axis. Regular magnetic poles are formed at the ends of the magnetic layer of the memory cell 14. The associated magnetic field lines close over the outer space in the manner shown. They penetrate the adjacent metallic base plate 10 similar to when the field

709 519/376

run in air, since the relative permeability of the metals used is sufficiently small the permeability in air differs. In the soft magnetic material 30, on the other hand, there is the course of the field much more concentrated due to the higher permeability, which is due to two closely adjacent ones Field lines is indicated.

F i g. 5 b shows in a similar way the field profile immediately after the rotation switching of the magnetization of the magnetic layer, when the original magnetic field has been retained because of the finite relaxation time of the magnetic material. The memory cell viewed from the longitudinal edge is denoted by 14. It is located on the metallic base plate 10. The bit line B, which is visible in cross section, is a strip line provided with slots and consists of four parallel conductors. Other drivetrains necessary for operating the accumulator, as well as insulating intermediate layers or intermediate layers for improving the adhesion, are omitted from this schematic drawing. Within the memory cell 14, the symbolic representation of the induction B _F by means of arrow springs by an inclined cross indicates that the magnetization now points backwards away from the viewer and thus points in the hard direction. In the outer space, the magnetic field Hp, H _A , H _{M is} still formed in the same way as drawn as before in the case of the static field profile. This is because the induction B _M in the magnetic material 30 has not yet disappeared and is therefore trying to maintain the previous field profile. Although no magnetic poles can now be formed on the two outer front edges of the memory cell 14, since the magnetization is supposed to be switched in the hard direction under the compulsion of an externally acting driving field, the field lines try to close as in the previous way. This explains why the field lines H _P, some of which have been forced out of the memory cell 14, then tend to switch the magnetization of the memory cell 14 back to the original rest position in the easy direction if the drive pulse has its effect on driving the magnetization in the hard direction in good time loses.

These relationships are explained with reference to FIGS. 6a and 6b, which show the time-dependent course of the induction associated with the bit field or the magnetic field strength proportional to it / ^ in the immediate vicinity of the memory cell during the non-destructive reading process and the associated word drive pulse i _w . One can distinguish three sections. In the static case, ie when a binary value is stored in the memory cell, the induction B ^ in the soft magnetic material has a certain constant value. Correspondingly, the proportional magnetic field fl ^ in the vicinity of the memory cell is constant. A word drive current i _w does not yet flow. The word driving field is active in the second section of duration T _1. As can be seen from the time-dependent course of the word drive current i _w (t) shown in FIG. 6b, the word drive pulse is almost rectangular. During this time the magnetic field changes _A falling exponentially with a time constant T, similar to that explained above with reference to FIGS. 4a and 4b.

If, by selecting a suitable magnetic material with a time constant that is about twice as large as the duration of the word drive pulse, one ensures that a certain field H _{crU is} still present at the end of the time T _t , then non-destructive reading is possible of the magnetic layer memory possible. Because this field H _{cri /} then supplies the necessary back driving field components, which after the end of the word driving field the

ίο Let the magnetization of the memory cells fall back into their original rest position. The size of the virtual bit field H _{crit, which can} be used for non-destructive reading, must be approximately 0.3 to 0.5 times the value of the bit field that would otherwise be generated by applying bit pulses to the bit lines. Writing binary information is created. In the third section, when the word driving field has subsided, the magnetic field ₄ in the vicinity of the memory line rises again exponentially with the time constant T to its original constant value.

In the F i g. 7 a and 7 b shows another possible arrangement of the magnetic layer memory cells in relation to the adjacent soft magnetic material. In addition, use is made of the eddy currents associated with the magnetic switching processes in these arrangements. Instead of an electrically conductive base plate 10, the storage cells 14 are arranged here on a ferrite plate 30. This ferrite plate has an electrically conductive layer on its surface, which z. B. may consist of vapor-deposited copper. This thin metal layer serves on the one hand as a return conductor for the drive lines of the memory arrangement, on the other hand, eddy currents are generated in it by the magnetic switching processes, which can also be used for non-destructive reading of the information. Only one bit line B, which is visible in cross section and consists of four strip lines, is shown above the memory cell 14. All other drive lines and interlayer layers are omitted for the sake of clarity.

The F i g. 7 a schematically shows a memory cell 14 in the case of the static field, ie in the rest position of the magnetization. The direction of the easy axis of magnetization corresponds to the direction of the arrow M. At the ends of the magnetic layer of the memory cell 14, regular magnetic poles are formed. The associated magnetic field lines are essentially closed in the manner shown by the ferromagnetic layer 30. FIG. 7b shows in a similar manner the field profile immediately after the rotational switching of the magnetization of the magnetic layer in the hard direction when the original magnetic field is in the vicinity of the memory cell 14 is maintained by the joint action of the magnetic induction still present as a result of the finite relaxation time of the magnetic material 30 and the field of the eddy currents in the metallic layer 70. The magnetic layer memory cell viewed from the longitudinal edge is designated by 14. Above that, the bit line B, which is divided into four, runs perpendicular to the plane of the paper . Inside the memory cell 14, the symbolic representation of the arrow springs by means of inclined crosses indicates that the magnetization M now points backwards away from the viewer and thus into the hard one

Direction. Outside, d. H. essentially in the ferrite plate 30, however, the magnetic field is still in the same way as shown designed as before in the case of the static field profile.

With this arrangement, too, non-destructive reading of the information is possible. The magnetic one Flux of the magnetic layer memory cell penetrates through the contiguous copper layer and closes essentially via the ferrite base plate. The magnetic resistance can thereby be kept small that the paths in copper or other electrically conductive material through Reducing the layer thickness should be made as short as possible. Next sets as high as possible Permeability of the ferrite plate or that otherwise arranged in the vicinity of the magnetic layer memory cells magnetic material decreases the magnetic reluctance. This is a much cheaper arrangement of a magnetic layer storage device than the previously common arrangement with relatively large air passages in the vicinity of the memory cells. The stray fields of the magnetic layer memory cells are now smaller, and therefore the edge domains that occur are also with oppositely directed magnetization direction tiny. This causes possible disturbances in the memory operations by influencing the information content of the memory cells lower due to the so-called creep of magnetization.

Another advantage of the arrangement is to be seen in the fact that now the strip lines supplied Driving impulses can run back in the cohesive metal layer. The effective electric The resistance of the return line can be kept very small, which increases the usable cable length. This means that larger magnetic layer memories are used accordingly increased storage capacity possible. This arrangement is also favorable for achieving good read signals. When the word driving field spreading with the driving pulses running over the strip lines arrives at the location of a magnetic layer memory cell, the magnetization of the memory cell in switched the hard direction. The eddy currents that occur very quickly push the metal layer the magnetic field of the memory cell changing its state of magnetization into the outer space, d. H. practically in the vicinity of the reading line. Relatively large read signals are thus induced. If so However, the word drive pulse was short enough to provide the relatively slower decaying magnetic induction the virtual bit field in the magnetic material adjacent to the magnetic layer memory cells, to reset the magnetization of the magnetic layer memory cells to the original rest position.

Claims (11)

Claims: 60 1. Magnetic layer memory with thin-layer memory cells having a magnetic easy axis for storing binary information, orthogonally with the memory cells adjacent running bit and word drive lines, of which the word drive lines are parallel to the easy axis run and received query pulses supplied when extracting information, the a magnetic field for an information-destroying deflection of the magnetization of a memory cell Generate transversely to the easy axis, with read lines, depending on such Deflection of the magnetization of a memory cell can be induced with read pulses a yoke made of soft magnetic material adjacent to the memory cells, which absorbs the leakage flux the memory cells partially takes up, and read out with means for rewriting Information, characterized that the material of the soft magnetic yoke has a relaxation time for changes in the Has magnetic state, which is in the order of magnitude of the duration of the interrogation pulses and that the duration of an interrogation pulse with respect to the relaxation time of the yoke material is tuned so that the magnetic field when the interrogation pulse decays in the yoke residual magnetization still present after the information has been extracted, a reset of the memory cell into the magnetization state that existed before the start of the interrogation pulse caused. 2. Magnetic layer memory according to claim 1, characterized in that the yoke material has a relative permeability μ > 10 and a relaxation time with a time constant T - 5 to 20 nanoseconds. 3. Magnetic layer memory according to claim 1 and 2, characterized in that the relaxation time constant (Γ) of the yoke material is about twice as large as the duration (T ₁ ) of the interrogation pulse (i _w ) . _{4. Magnetic layer memory according to Claims 1 to 3, characterized in that the virtual rewriting} bit field (H crit) still present after the interrogation pulse has died down due to the residual magnetization of the yoke reaches approximately 0.3 to 0.5 times the value of the bit field that otherwise, when writing information, it is created in the direction of the easy axis. 5. Magnetic layer memory according to claims 1 to 4, characterized in that the virtual rewriting bit field resulting from the utilization of the inherent relaxation time of the yoke material is additionally supported by the field of eddy currents induced in electrical conductors (70, B, BSI). 6. magnetic layer memory according to claims 1 to 5, characterized in that as a soft magnetic yoke plate-shaped ferrite body in a plane parallel to the plane of the Magnetic layer memory cells are arranged. 7. magnetic layer memory according to claims 1 to 5, characterized in that as a soft magnetic yoke finely divided ferrite in a cohesive layer of binder is arranged in a plane parallel to the plane of the magnetic layer memory cells. 8. magnetic layer memory according to claims 1 to 4, characterized in that as a soft magnetic yoke finely divided magnetic substances such as carbonyl iron or HF iron in a coherent binder layer in a plane parallel to the plane of the magnetic layer memory cells are arranged. 9. magnetic layer memory according to claims 1 to 4, characterized in that as a soft magnetic yoke, thin magnetic layers in a plane parallel to the plane of the magnetic layer memory cells are arranged. 10. magnetic layer memory according to claim 9, characterized in that as soft magnetic Yoke serving thin magnetic layers are magnetically isotropic. 11. magnetic layer memory according to claims 1 to 8, characterized in that the base plate of the memory matrix made of magnetic material (30) with an electrically conductive Surface layer (70) consists (Fig. 7). Considered publications: German Patent No. 948 998; British Patent No. 895248; U.S. Patents Nos. 3,015,807, 3,030,612, 077,586, 3,092,816; French Patent Nos. 1 303 405, 321 622; “Trans. AJEE ", pt. 1, vol. 72, January 1954, p. 822 to 830; "Journal of Applied Physics", Suppl., April 1959, pp. 54 S and 55 S; “Proceedings Intermag. Conference, '1963, pp. 9-5-1 to pp. 9-5-14. 1 sheet of drawings