JPH01184782A - Bloch line memory element - Google Patents

Abstract

PURPOSE:To prevent the generation of malfunction at the time of transfer to attain effective memory operation by providing a transfer auxiliary conductor on a stripe magnetic domain end part where a transfer period is extended. CONSTITUTION:Since the stripe magnetic domain 2 can not be invaded into a groove 8, the magnetic domain 2 is fixed around the groove 8 and can be stably positioned and a pair of Bloch lines are transferred along a magnetic wall by regarding a position under a transfer route pattern 7 as a stable position. Since a transfer auxiliary conductor 15 is provided on the stripe magnetic domain end part, energy potential sensed by a pair of Bloch lines is obtained by impressing a magnetic domain generated from the transfer auxiliary conductor, the depth of the energy potential at position gamma becomes small due to the magnetic field and new driving force is applied to the pair of Bloch lines. Thereby, transfer characteristics similar to that of other areas can be obtained even between gamma and delta where the transfer period is extended. Consequently, a transfer error can be improved and a memory operation range can be expanded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state magnetic memory, and particularly to a Bloch line memory suitable for a large-capacity file memory.

[Conventional technology]

Like the magnetic bubble memory element, the Bloch line memory element uses a magnetic garnet film as a storage medium. The magnetic garnet film is formed so that its film surface is a (111) plane. However, the storage methods of the two are significantly different. That is, in a conventional magnetic bubble memory element, the presence or absence of a bubble domain corresponds to the information ll, 'Q+, whereas in a Bloch line memory element, the presence or absence of a bubble domain corresponds to the vertical Bloch domain wall that exists around a stripe domain that is an elongated bubble domain. Information 11' indicating the presence or absence of line pairs.

It corresponds to '0'. This situation is shown in FIG. 3. In FIG.
The direction of magnetization in the domain wall 1, the arrow 5 in the domain wall 1 is the direction of the domain wall magnetization,
In particular, an arrow 101 on the center line within the domain wall 1 indicates the direction of domain wall magnetization at the center of the domain wall 1, and an arrow 102 perpendicular to the plane of the domain wall 1 indicates the center of a vertical Bloch line (hereinafter simply referred to as Bloch line). The direction of magnetization of each part is shown.

Here, the part 4 where two Bloch lines 3 exist
A corresponds to '1'' with information, and the portion 4b without information corresponds to 10'.

The Bloch line pair 4a used as an information carrier is a fine magnetized structure existing in the domain wall 1 surrounding the striped magnetic domain 2, as shown in FIG. Bloch line 3 is domain wall 1
It exists stably inside and.

It can move freely within the domain wall 1. therefore,
If a large number of striped magnetic domains 2 are arranged in parallel and Bloch lines 3 are present in the domain walls, a storage section like the minor loop of a magnetic bubble memory can be constructed.

The existence of such Bloch lines has been known for a long time, and it has been proven through experiments and analyzes that their existence slows down the movement speed of magnetic domains. Therefore, in magnetic bubble memory devices in which magnetic domains must be moved, bubble magnetic domains containing Bloch lines are called hard bubbles, and efforts have been made to prevent their generation. On the other hand, Bloch line memory elements actively utilize the existence of Bloch lines.

The physical size of a Bloch line is approximately 1710 times the width of a stripe magnetic domain where a Bloch line exists, and 1
A large number of Bloch lines can exist in the striped magnetic domain of a book. For example, in the case of magnetic garnet with a stripe domain width of 1 μm, which is currently being developed for magnetic bubble memories, about 5×10 6 Bloch lines can exist in 1 d. Therefore, when the two are used as a pair of information carriers, a 256 Mbit/c1 class memory element can be produced.

In addition to the fact that the Bloch line is small in size, there is a reason why the capacity can be increased. This is because the magnetic bubble memory element transfers information by rotating an in-plane magnetic field, whereas the Bloch line memory element transfers information using a magnetic field perpendicular to the magnetic garnet film surface. This is because the transfer path pattern has a planarly simple shape and configuration, which facilitates increasing the density of elements.

As described above, Bloch lines freely circulate around striped magnetic domains and can store information. In order to write or read this information as necessary, it is necessary to provide a new functional section outside the storage section. FIG. 4 schematically shows a Bloch line memory element. The storage section is composed of a large number of striped magnetic domains 2. The transfer path pattern 7 is provided so as to intersect with the striped magnetic domains 2 at approximately right angles. The readout function section 121 is located on the right side of the striped magnetic domain 2,
The write function section 120 is provided on the left side of the striped magnetic domain 2.

Bloch line writing is performed by passing a current through a conductor formed near the left end of the striped magnetic domain 2.

This is done by generating a local magnetic field and inverting the magnetization of the domain wall by 180'. That is, the magnetization of the 'O' (4b) region shown in Fig. 3 is reversed and the magnetization is '1'.
(4a) This is done by setting the magnetization direction of the region. At this time, the magnetization changes continuously at the boundary between the inverted region and the non-inverted region, creating a state in which the magnetization changes by 90° with respect to the domain wall. This is the Bloch line. Note that at this time, since two Bloch lines are always created in pairs, a memory is constructed by associating this pair of Bloch lines with one piece of information.

At this time, in order to avoid writing L OJ, that is, Bloch lines, in the striped magnetic domain, it is sufficient to increase the distance between the left end of the striped magnetic domain 2 and the writing conductor. As a result, the magnetic field that causes magnetization reversal no longer acts on the striped magnetic domain 2. In order to separate only a desired striped magnetic domain from the write conductor, a means is used that causes magnetic bubbles 10 to exist at the ends of the striped magnetic domains. When the magnetic bubble 10 exists, a magnetostatic repulsive force acts on the left end of the striped magnetic domain 2,
Stripe magnetic domain 2 shrinks. Therefore, the above positional relationship is realized. In order to cause this magnetic bubble to exist in the write function section 120, the write function section 120 is provided with a magnetic bubble transfer path 110 and a magnetic bubble generator 11. The magnetic bubble transfer path 110 transfers the magnetic bubble 10 from the magnetic bubble generator 11 to the left side of a predetermined stripe magnetic domain 2. Information is read by converting the presence of Bloch lines into the presence or absence of magnetic bubbles. The conversion from Bloch lines to magnetic bubbles is explained by Konishi, I.E., Transactions on Magnetics-19, No. 15 (1983), pp. 1838 to 1840 and pp. 1841 to 1843 (
IEEE Trans, on Mag-19Nn15
(1983) p1838-p1840. p1841-p
1843) is used. That is, when a Bloch line exists, the direction of magnetization of the domain wall is reversed with the Bloch line as a boundary. When one Bloch line moves to the end of a striped magnetic domain due to this change in the magnetization structure, the ease with which the end of the magnetic domain is cut out changes. Therefore, if predetermined cutting conditions are selected, a magnetic bubble can be cut out only when one Bloch line exists at the end of a striped magnetic domain. This extraction is performed by the readout function section 121 shown in FIG. The extracted magnetic bubbles are transferred to the magnetic bubble detector 12 via the readout transfer path 111, where the presence of the magnetic bubbles is converted into an electrical signal. The presence or absence of this electric signal corresponds to the presence or absence of a magnetic bubble and the presence of a Bloch line (information) at the end of a predetermined stripe magnetic domain. Reading cannot be performed by the above operations.

FIG. 5 shows the end of one striped magnetic domain 2 constituting the storage section. Stripe magnetic domain 2 is magnetic garnet 6
It exists so as to surround the groove 8 (referred to as grooving) made inside. This groove has a function of fixing magnetic domains in order to arrange a large number of striped magnetic domains in parallel. Information is stored corresponding to the presence or absence of Bloch line pair 4. This Bloch line pair 4 is transferred in the domain wall by the perpendicular magnetic field Hp and the transfer path pattern 7.

Here, we will briefly discuss the transfer principle of Bloch line pairs. When a magnetic field perpendicular to the film surface is externally applied to the Bloch line, a force based on the gyroscopic properties of the Bloch line acts in the film surface direction. This force causes the Bloch line pair to move within the domain wall.

However, when this perpendicular magnetic field is cut off, a force in the opposite direction acts, and the Bloch line pair has the property of returning to its parent position. Therefore, in order to move the Bloch line pair in one direction, it is necessary to make a difference between the force that advances the Bloch line pair and the force that returns the Bloch line pair.

It is known that this driving force is proportional to the falling speed of the magnetic field, and by applying a triangular HP magnetic field pulse as shown in the figure, unidirectional transfer can be achieved.

By the way, when configuring a memory, the location where information exists must always be stable and have good reproducibility. Using the above technology, it is possible to circularly transfer the Bloch line pair in one direction, but in this state, the position of the Bloch line pair will shift due to disturbances in the external magnetic field, etc.
There is a risk of information being lost. Therefore, a transfer path pattern is provided in the storage section, and it is easier to stably exist protpho line pairs directly under the pattern compared to other areas (on the contrary, the same effect can be obtained by making the area without a pattern stable). . In addition, the strength of the driving magnetic field f (p is set within a certain range,
A pair of Bloch lines can be moved to an adjacent stable position with one driving field pulse. By doing so, the Bloch line pair becomes stable against disturbances smaller than the driving magnetic field, and can always be moved by a uniform distance.

In order to stably exist the Bloch line pair, a pattern such as a high coercive force in-plane magnetized film is used for the transfer path pattern 7 shown in FIG. If such a material is used for the transfer path pattern 7, a leakage magnetic field 104 as shown in the figure can be obtained. (In order to obtain this magnetic field, it is necessary to magnetize the pattern in advance in the longitudinal direction of the striped magnetic domains. Therefore, the direction of easy magnetization of the film must be within the film plane. It is necessary to have a high coercive force so that the magnetization state of the pattern is not disturbed by the leakage magnetic field from the magnetic field.)) The direction of this leakage magnetic field 104 and the magnetization direction 105 of the area surrounded by the Bloch line pair 4 are made to match. If you let me.

The Bloch line pair is energetically stable directly below the transfer path pattern 7. Therefore, the Bloch line pair always exists directly below the transfer path pattern 7.

Therefore, when this transfer path pattern 7 is provided and the driving perpendicular magnetic field HP is applied, the Bloch line pair corresponding to information always moves by a predetermined amount and becomes stable even against disturbances. Therefore, information storage is realized.

However, in the conventional Bloch line memory element described above, malfunctions are likely to occur when the Bloch line pair passes through the ends of striped magnetic domains.

Good memory performance was not obtained. The cause of this will be explained using FIG. 6(a). FIG. 6(a) is a cross-sectional view taken along the line A-A in FIG. 5, expanded in the horizontal direction. handle.

The figure shows the energy potential of Bloch line pairs directly below these transfer path patterns. That is, in the Bloch line pair, a valley of energy potential corresponding to the transfer path pattern stably exists. Assume now that the Bloch line pair 200 exists at positions α, β, and γ in the figure. In this state, when a perpendicular magnetic field J (P) that drives the Bloch line pair is applied, the Bloch line pair should move, overcome the potential peak, and move toward the adjacent potential valley.However, the edge of the stripe magnetic domain The distance between the stable position corresponding to γ and the adjacent potential valley.

C becomes far away because the domain wall is curved. For this reason, γ
The Bloch line pair existing at the position is transferred under the condition that the Bloch line pair existing at the other potential valley is transferred.
Causes malfunction.

In order to prevent this malfunction, the transfer periods b and C in FIG. It is enough to explain many times according to the shape (for example, radially). However, with this method, new problems arise because it becomes difficult to position the transfer path pattern and the ends of the striped magnetic domains, and the transfer path pattern must be made with extremely high precision. (Normally, the transfer path pattern in the straight section can be easily created using optical diffraction method).

Furthermore, it is thought that the above problem will not occur even if the transfer path pattern period is widened to about the stripe magnetic domain width. However, with this method, it is not possible to realize a large-capacity file memory that takes advantage of the Bloch line's fineness.

[Problem that the invention seeks to solve]

In the conventional technique described above, transfer errors tend to occur at the ends of striped magnetic domains. This is because the transfer period at the ends of the striped magnetic domains is longer than at the straight parts. In the conventional technology,
No consideration was given to this issue. For this reason, good memory operation could not be obtained.

An object of the present invention is to prevent malfunctions during transfer at the ends of striped magnetic domains where the transfer period is long, and to realize good memory operation.

[Means for solving problems]

The above object is achieved by providing transfer auxiliary conductors at the ends of striped magnetic domains where the transfer period becomes longer.

[Effect]

When a current pulse is passed through the transfer auxiliary conductor, a magnetic field containing a component equal to the perpendicular magnetic field that drives (transfers) the Bloch line pairs acts on the ends of the striped magnetic domains.

As a result, the Bloch line pair receives a strong driving force and can move over a long distance, making it possible to prevent malfunctions at the ends of the striped magnetic domains.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The magnetic garnet substrate has a thickness of 1.0 μm (YS+nL
uGd) a(FeGa) aO engineering garnet was used.

In order to fix the striped magnetic domains, grooves 8 were dug in this magnetic garnet. After flattening this groove with polyimide resin, a transfer path pattern 7 was formed. Specifically, 1000 NiCoZr films were deposited on the film surface by sputtering, and then formed by photolithography. NiCoZ
The saturation magnetic flux density of the r film is approximately 8000G, and the residual magnetization is approximately 70
It is 0 emu/cc. Therefore, a leakage magnetic field of about 100 e was obtained directly under each pattern. Thereafter, an insulating layer was laminated, and then combined with the conductor of the information input/output functional section to form the transfer auxiliary conductor 15. These conductors were processed by photolithography after depositing Au.

The present invention will be described in detail using the same figure. The striped magnetic domains 2 cannot penetrate into the grooves 8.

Therefore, the stripe magnetic domain is fixed around the groove 8,
can exist stably. The Bloch line pairs written in the magnetic domain wall of this striped magnetic domain have a stable position immediately below the transfer path pattern 7, and are transferred along the magnetic domain wall.

Next, a case will be described in which the Bloch line pair is transferred to the end of the striped magnetic domain. Since the transfer auxiliary conductor 15 is provided at the end of the stripe magnetic domain, the energy potential felt by the Bloch line pair is as shown in FIG. 6(b). Figure 6(b) is similar to (a), and B- in Figure 1.
It shows the energy potential along line B. now,
The Bloch line pair 200 is a perpendicular magnetic field Hp (driving magnetic field)
When transferred from α to β and from β to γ.

A magnetic field generated from the transfer auxiliary conductor is applied to the Bloch line pair existing at the position γ. Due to this magnetic field, the energy potential at the position of γ becomes shallower, and a new driving force acts on the Bloch line pair.

As a result, transfer characteristics similar to those in other regions can be obtained even between γ and δ, where the transfer period is long. Note that the milk layer between β and 7 is also long, but in this case the distance from the position of β to the peak of the potential is short, so this period did not pose a problem from the beginning.

The shape of the transfer auxiliary conductor described above is not limited to the shape shown in FIG. 1, but may also be the shape shown in FIG. 2 (a) and (b). The Bloch line that existed at the edge of the stripe magnetic domain,
A necessary condition is to provide a driving force in the transfer direction. or,
To achieve this.

The polarity of the current pulse IP to be applied had to be selected after considering the positional relationship between the striped magnetic domain and the transfer auxiliary conductor.

Further, the period of this current pulse Ip had to be equal to the period of the perpendicular magnetic field HP that drives the Bloch line pair. If the periods are different, the timing of the driving force will be shifted and the desired effect cannot be expected. Therefore, Ip current was applied at the timing shown in FIG. The figure (a) shows the vertical magnetic field H
This is the waveform when Ip current flows in exactly the same phase as p. In this case, the waveform was triangular in order to reduce the influence on the Bloch line pair when Ip was turned off.

Furthermore, when the rectangular pulse (b) is used, the influence after turning off the IP tends to remain behind, so it is necessary to make the phase earlier.

Furthermore, although the driving force applied to the Bloch line pair becomes weaker, the present invention could be implemented with the sinusoidal current shown in FIG. 7(c) for the purpose of shallowing the energy potential.6 As described above, (a) to ( No matter which of the waveforms c) was used, transfer defects at the ends of striped magnetic domains could be improved.

It should be noted that the present invention could be put to practical use not only at the edges of striped magnetic domains, but also for improving transfer defects and transfer characteristics in straight portions.

〔Effect of the invention〕

According to the present invention, transfer errors of Bloch line pairs at the ends of striped magnetic domains can be improved. As a result, the memory operating range has been expanded by approximately 50%.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an end of a storage section showing an embodiment of the present invention, FIG. 2 is a diagram showing another embodiment, and FIG. 3 is a diagram showing a magnetic garnet film and Bloch lines existing therein. FIG. 4 is a block diagram of the Bloch line memory element, and FIG. 5 is a diagram showing the structure of the end portion of the memory section. FIG. 6 is a diagram showing the energy potential created by the transfer path pattern, and FIG. 7 is a diagram showing the relationship between the phase of the current flowing through the transfer auxiliary conductor and the phase of the driving magnetic field. DESCRIPTION OF SYMBOLS 1... Domain wall, 2... Stripe magnetic domain, 4... Protube line pair, 6... Magnetic garnet, 7... Transfer path pattern, 8... Groove, 15... Transfer auxiliary conductor . Figure 1 and Figure Z (first)

Claims (1)

[Claims] 1. Bloch line pair, which is present in the domain walls of a plurality of striped magnetic domains arranged in parallel in a magnetic garnet film whose easy magnetization direction is perpendicular to the film surface, is used as an information carrier. A Bloch line memory element characterized in that a transfer assisting conductor is provided at the end of a stripe magnetic domain constituting a storage section. 2. In claim 1, the Bloch line pair is driven by an applied magnetic field perpendicular to the film surface,
A Bloch line memory element characterized in that the effective magnetic field applied by the transfer auxiliary conductor to the edge of the striped magnetic domain has a magnetic field component at least equal to the applied magnetic field. 3. The Bloch line memory cable according to claim 1, wherein the current pulse applied to the transfer auxiliary conductor is always applied in synchronization with the applied magnetic field for transfer.