JPS59191189A - Magnetic memory element - Google Patents

Abstract

PURPOSE:To increase memory density remarkably by constituting a monor loop of a strive domain existing in the bubble material and using VBL in place of a bubble domain as unit of information on the minor loop. CONSTITUTION:Information (presence or absence of bubble) written in a generator 1 moves a write major line from up to down. To store this information in a minor loop 2, the minor loop is constituted of a Bloch magnetic wall that can hold VBL so that information on the major line indicated by the presence or absence of bubble 3 can be transferred in the form of VBL to the minor loop of an information accumulating section. Information (VBL) transferred to the minor loop by a write line transfer gate 4 can be moved on the strive domain magnetic wall, and the information transfer from the minor loop to the read major line is accompanied by conversion from VBL to bubble. This read transfer gate 5 also has function of block replicator.

Description

[Detailed description of the invention]

The present invention uses vertical Bloch lines, which are statically and stably present in the Bloch domain walls forming the boundaries of striped domains formed in a ferromagnetic thin film whose easy magnetization direction is in the direction perpendicular to the film, as a memory unit. The development of magnetic bubble elements, which are related to magnetic memory elements, has become active in various places with the aim of increasing density, such as permalloy devices, ion-implanted continuous disk devices, current drive devices, and so-called hybrid devices that combine these. It is being done. It has been said that the limit to the high density of these devices lies in the funatori/graphic technique for forming the bubble transfer path. However, in recent years, the technology has advanced rapidly. As a result, attention has been paid to materials for increasing density, ie, to what extent the bubble diameter can be reduced. With the currently used garnet materials, the minimum attainable baffle 81 is said to be 0.3 μm. Therefore, a bubble material that retains bubbles with a diameter of 0.3 μm or less must be found other than Carnet material.

[No need to. This is not easy, and it is even considered that this is the limit for increasing the bubble rate. The present invention is based on the characteristics of such a bubble retaining layer (a memory element that can greatly improve the high politicalization limit and keep the information read time at the same level as conventional elements). The present magnetic memory element includes an information reading means, an information writing means, and an information storage means, and includes a ferromagnetic film whose easy magnetization direction is perpendicular to the W plane. (including the magnetic film) around the stripe domain
] The present invention is characterized by using a pair of adjacent vertical Proch lines (hereinafter referred to as VBL) formed in the Blotzbo wall as a storage information unit, and having means for transferring the vertical Proch lines within the Bloch domain wall. FIG. 1 is an overall view of the chip of the present magnetic memory element. To show the overall flow of information, first, the information written by the generator 1 (the presence or absence of bubbles) moves from the top to the bottom of the subtraction major line. In order to store this information in minor loop 2, the minor loop is transferred to VBL so that the information on the major line indicated by the presence or absence of bubble 3 can be transferred to the minor loop of the 1W information storage section in the form of VBL.
The feature of this magnetic memory element is that it is composed of Bloch domain walls that can hold L, and is an important key to dramatically improving storage capacity. Marriage line transfer gate 4
The information transferred to the minor loose by
VBL) can move the striped domain domain wall soil that constitutes the minor loose. Information transfer from the minor loop to the read major line is done by VB.
Involves conversion from L to bubble. Note that this read transfer gate 5 also has a block replicator function. In this way, when the minor loop is composed of striped domains existing in the bubble material, and when VBL is used instead of the bubble domain as the information unit on the minor loose, it is approximately A two-digit increase in storage density can be achieved. Further, a configuration example and an operation example of each part of this device will be explained. The major line uses a current drive method for both writing and reading. The transfer gate, which consists of four parallel conductors, is 0.0 mm on the major line. Construct bubbles and minor loops. It uses interaction with the striped domain head. When there is a bubble domain on the major line line, the heads of the stripe domains forming the minor loop connected to it move away from the bubble due to the repulsive interaction between the bubble and the stripe domain. When there is no bubble on the write major line, VHL is written on the minor loose stripe domain domain wall. Vf
3L into a stripe domain head, a pulse current is applied to a conductor pattern in contact with the stripe domain head so as to dynamically move the conductor pattern to dynamically converge the head domain wall. This method creates two VBLs, which have different properties and are easy to recombine. Therefore, in order to stabilize the information, an in-plane magnetic field is applied in the longitudinal direction of the strife domain, and the stripe domain head is separated by two conductors on the stripe domain side. Create these two VBLs with the same properties. VBLs with the same properties stably exist even if they are brought close to each other. The minor loose stripe domain head corresponding to where the bubble exists on the major line is away from the conductor pattern due to the repulsion with the bubble, so the VBL
is not formed. As a result, major line information ゛1''
is transferred assuming that there is no VBL pair in the minor loop. In the minor loop, information is stored using a pair of VBLs with the same properties as one bit. Considering the stability of the replicator action, we use the ○VBL pair. A transfer pattern is set so that bits can be selectively transferred one by one so as to keep the bit period within the minor loose, that is, the vBL interval, constant. - As an example, a stable interval 5o (71
A parallel thin line pattern made of a Permalloy (η) film with a width S0 was formed with twice the period, and the interaction between the magnetic poles and VBL induced on both sides of the parallel thin line was used as %ij. One way to transfer the VHL along the minor loose is to dynamically apply a pulsed bias magnetic field to the stripe domain. A readout transfer gate consisting of three parallel conductors converts the information stored as a striped domain domain wall (VF) (L) forming a minor loop into a bubble and transfers it out to the major line. There is also a replicator function that prevents the above information from being destroyed.The operating principle is explained.For example, one half of a single head formed by a VBL pair is formed by applying an in-plane magnetic field to create a striped domain head. Then, make a conductor pattern II and cut out this striped domain head.
7＼Pull. Then, the same VBL as the cut VBL is created in the striped domain head after the bubble is cut. Such a VBL replication effect occurs only for a VBL with a minus sign. The bubble cut from the minor loose striped domain head is transferred along the major line toward the detector. Here, it is used that the pulse current value for cutting off the striped domain head is different depending on whether the striped domain head has VBL or not. If there is no VBL on the striped domain head, it will be difficult to cut. Therefore, if there is a VBL in the striped domain head, a bubble can be sent to the major line, but V
If there is no J3L, there is no bubble. In other words, the presence or absence (1, 0) of VRL on the minor loop is converted to the presence or absence of a bubble on the read major line. The elimination method for VBL pairs will be described. Place the VBL pair to be erased at the position closest to the minor loose stripe domain head on the writing major line side. Next, apply an in-plane magnetic field Hip to the VBL pair you want to erase.
Strife is one half of the VBL pair next to it. Bring it to the domain head and use it to cut off the positive VBL when writing information, and use a parallel conductor to cut off the striped domain head. After cutting out the bubble domain, the VBL brought along with the erased &) VBL pair is replicated in the Q] stripe domain head. In the end, only the VBL pair that is desired to be erased will be erased. In addition, if you want to clear the entire minor loop,
After increasing the bias magnetic field and erasing all σ) stripe domains, create a state where VBL does not heat up at all by forming a purkara minor loop drive domain in S-1. I can do it. In such a magnetic memory element, it is essential to have a means to stably maintain the 0+ VBL on the striped domain domain wall written as information. That is, an object of the present invention is to provide an information level stabilization means suitable for the above-mentioned magnetic memory element in which VHL is an information unit. In a magnetic memory element that uses a pair of adjacent vertical Ploch lines formed in a Bloch domain wall around a stripe domain existing in a ferromagnetic film whose easy magnetization direction is perpendicular to the film surface as a storage information unit. , is a magnetic memory element whose characteristic is that the direction of magnetic anisotropy within the film plane changes locally along the Bloch domain wall. As a method for stabilizing the position of the VBL, a method of placing a pattern made of a ferromagnetic film on the film surface and utilizing magnetostatic interaction with the VBL or with the a-wall magnetization between a pair of VBLs can be considered. However, in the case of magnetostatic interaction, the interaction with the magnetic domains on both sides of the domain wall other than the interaction with VBL is large, and there is a considerable problem in stably driving V) (L. Since only the potential energy of the VBL can be changed locally without using interaction, the motion of the domain wall, which plays an important role in driving the VBL along the stripe domain domain wall, is hardly inhibited. Let me explain the background: VBL in a magnetic bubble
O) J @lRegarding this, the following seven items are being sold. A magnetic bubble (hereinafter referred to as a bubble) is a VBL containing a Bloch point and a VB without a Bloch point.
The so-called (+, 2.1) state (number of windings ÷, VBL is 2, Bloch point is 1)
1), a static image magnetic field np is applied in the in-plane direction of the film containing the bubble, and the bubble is driven by applying a bias magnetic field gradient. Then, when the domain wall velocity V becomes equal to or higher than Vcrit given by the relationship with Hp, VBL without Bloch points moves at the position of VBL with Bloch points, and both VBLs collide and annihilate each other. The state changes to (1%0.0). Because VBJ has Bloch points. This is because the bubble does not move at all even if you move it. Here, Δ is the domain wall width parameter of the striped domain domain wall,
(A/, K11 house/person has conversion stiffness constant a,
Ku is the uniaxial magnetic anisotropy energy of the striated magnetic retention layer. γ is the gyromagnetic fi constant of the striped domain retention layer. V (below Vcrit, VBL does not recombine with other VBLs due to the restoring force 2MπΔHp based on Hp, and V
=Ot If you do this, position I will minimize the Zeeman energy between Hp and the magnetization of the protube domain walls on both sides of Vf3L. Here, M represents the magnitude of magnetization of the striped domain retention layer. This honey a
143 (1977). In other words,
In this case, Hp shows that the VBL position can be fixed. By examining the contents of this phenomenon in more detail,
The following is considered. If instead of the external magnetic field Hp, we apply a magnetic anisotropy field Hkip within the film surface whose direction is the direction of easy magnetization in the back surface (the direction with the lowest magnetic energy is perpendicular to the film surface), VB
It is easy to see from the evaluation of magnetic energy that in the case of a bubble, VEL is at both ends of a diameter parallel to Hkip. If there is, VBL
Since the magnetization of is oriented perpendicular to the domain wall surface, Hk
If ip is locally attached in a direction perpendicular to the domain wall surface,
VBL is stabilized in that position. this)(kip+ζ
On the other hand, if Vcrit """Hkip is defined, when the domain wall velocity is made greater than vcrit, V
BL will escape from the votent wool centered at the stable position. When it reaches V(Vcrit, VBL cannot escape from its potential wool and changes to 2π by 4ΔHki
It stays at a stable point due to the restoring force p. In other words, by applying an initial velocity of V) Vcrit to the domain wall, VBL escapes from one stable point and moves toward the next stable point. When VBL enters the gravitational field of the next potential, if the domain wall velocity ■ is less than Vc r i , then ■! (L is stabilized at that position. In other words, a margin is given to the domain wall drive conditions when transferring VBL one bit at a time, and VJ3L transfer is stabilized. The present invention utilizes this principle to provide information stabilization means suitable for a magnetic memory element that uses VBL as an information unit.The present invention will be described in detail below using the Okushiri example.Second. The figure shows minor looseness in the information storage section of a magnetic memory element using VBL. The minor loop consists of striped domains.
A Bloch domain wall exists in the periphery 21. The direction of magnetization in the Ploch line domain wall surface can take two directions, clockwise 24 and counterclockwise 25, and a vertical Ploch line V)iL22.23 exists at the boundary thereof. The VBL section has upward and downward directions, and this pair represents a unit of information. Diagram M3 shows a more detailed structure of the VBL pair. VBL can move in the Bloch domain wall due to the gyrotrobital force generated by the pulsed bias magnetic field applied in the direction perpendicular to the film surface of the ferromagnetic film forming the stripe domain, but the 1γ is not aligned. In order to hold it accurately, it is necessary to periodically prepare a stable solution of ~VBL along the protubo line domain wall. However, there are some places near the stripe domain head and other necessary places where the periodicity is not necessarily constant. FIG. 4 shows the basic structure of the VB-J stabilizing and holding means according to the present invention, where 4] is a striped domain. 42 is a pattern mask. If the direction of Hkip is perpendicular to the Bloch domain wall on dice other than 1 of the pattern mask, and if the direction of Hkip is set along the pro-soho porcelain under the pattern mask, then for VBL) ikip is the Bloch domain wall. The potential wool is deeper in the no-turn mask (h) facing in the direction perpendicular to the direction. Therefore, VIJL is stably located there. is tilted in the diagonal plane. Therefore, if there is magnetic anisotropy in the film plane, the magnetization feels magnetic anisotropy. The domain wall around the striped domain is usually a Bloch domain wall, but at the Proch line it is a Neel domain wall. It has the same structure as a domain wall.In other words, the direction of magnetization of the domain wall is either parallel to the domain wall or perpendicular to the domain wall.The interaction between these magnetizations and in-plane magnetic anisotropy is Thinking about it,
Areas where magnetic anisotropy is perpendicular to the domain wall surface are stable regions for Ploch lines, where magnetization is tilted in a direction perpendicular to the domain wall surface, and areas where magnetic anisotropy is parallel to the domain wall surface are stable regions. This is because it becomes a stable region for the Bloch domain wall that is tilted parallel to the domain wall surface. When a velocity greater than V (>ΔγHklp) is applied to the domain wall in this state, VBL escapes from its potential wool, moves along the domain wall, and gets stuck in the next potential cool. In this way, as a method of changing the direction of 4kip (along the Bloch domain wall), a striped domain retention layer has a magnetostriction constant of λ100. In the case of a material with λm, it is sufficient to implant hydrogen ions, helium ions, etc. outside the pattern mask to generate pressure stress there, as reported in Journal of Applied Physics 53 (1982) 58.
This is clear from the statement □2 on pages 15 to 5822. When ÷λ1oo+λ, 1□<0, Hkip becomes a direction perpendicular to the Bloch domain wall in the ion-implanted region, and this becomes a stable region for VBL. If +λ, o0+λ, I Incidentally, if a stripe domain retention layer in which the magnetostriction constants λ100 and λ1s1 are not equal is used and the stripe domains are arranged so that the in-plane (110) direction is the longitudinal direction, the above ion implantation can be performed. When stress is applied to the striped domain holding layer, the film orientation is <112 in the coaxial plane.
> direction (depending on the difference between λso. and λ11). Even when there is such an anisotropic magnetic field, it can be considered that for the VBL pair 22 and 23 in FIG. 3, it will be the same as when there is only a uniaxial anisotropic magnetic field. This is because the two magnetization directions differ as shown in Figure 2.
In BL 22.23, the magnetization is 180 across the domain wall width.
This is because the influence of the unidirectional anisotropic magnetic field on the Ploch line is averaged out because all the directions are taken over a range of .degree. If the stripe domains are arranged so that the in-plane (112) direction is the longitudinal direction, the above ion implantation will yield
When stress is applied to the striped domain holding layer, the in-plane (110) direction anisotropy magnetic field necessary for fixing VBL generated in the coplanar plane becomes a uniaxial anisotropy magnetic field. Figure 5 shows how these anisotropic magnetic fields are applied. Figure 6 shows how the magnetic anisotropy is applied when the longitudinal direction is the [11Z] direction in the plane.〇λ100 −λ
In the case of la+:>O, as shown in FIG. 5(a), in the region 51 where ions are not implanted, the stripe domain longitudinal direction [
112], and a uniaxial anisotropic magnetic field is generated in the ion-implanted region 52 in a direction perpendicular to the striped domain domain wall. λ100−λls, <0
In this case, as shown in FIG. 5(b), a unidirectional anisotropic magnetic field directed in the longitudinal direction [112] of the stripe domain is applied in the region 51 where ions are not implanted, and the ion-implanted region 5
2, a uniaxial anisotropic magnetic field is generated in the direction J perpendicular to the stripe domain domain wall. When λ100−λ, □1=0,
As shown in FIG. 5(c), a region 51 where ions are not implanted
In this case, a uniaxial anisotropic magnetic field is generated along the longitudinal direction of the striped domain, and in the ion-implanted region 52, a uniaxial anisotropic magnetic field is generated in a direction perpendicular to the striped domain domain wall. FIG. 6 explains how the in-plane magnetic anisotropy is created when +λ100+λ111 < O and the longitudinal direction of the stripe domain is the [120] direction in the plane. When λ100−λI11>0, as shown in FIG.
In the ion-implanted region 52, a unidirectional anisotropic magnetic field is generated in the [1.123 direction] perpendicular to the wall of the striped domain 7A. When λ1oo−λin < 0, Fig. 6 (bl
As shown in FIG. 3, in the region 51 where one ion is not implanted, a uniaxial anisotropic magnetic field is generated along the striped domain longitudinal direction (1103 direction), and in the region 52 where one ion is implanted, a unidirectional anisotropic magnetic field is generated in the [112] direction perpendicular to the striped domain domain wall. A directional magnetic field is generated. In the case of λ100-λIII"0, Fig. 6 (
c) l As shown, a uniaxial anisotropic magnetic field is generated in the non-ion implanted region 51 along the longitudinal direction [110] of the striped domain, and a uniaxial anisotropic magnetic field is generated in the direction perpendicular to the striped domain domain wall in the ion implanted region 52. Generates a magnetic field. It is obvious that a similar study can be made for the case where +λ1o λill > O. It is also obvious that the same thing can be said about each direction equivalent to [112] or [:11Q] in the plane. FIG. 7 shows an embodiment of the VBL stabilizing and holding means according to the present invention in a magnetic memory element, in which a large number of pattern masks 72 for ion implantation are attached to the wall of the stripe domain 7A as a large number of minor loops. . The pattern mask does not necessarily have to be composed of one (1) t3 phase, and may be partially narrow or wide. Further, the pattern mask does not necessarily need to intersect with a plurality of striped domains, and may of course be provided as an isolated pattern such as a circle or a rectangle on the Bloch domain wall clay according to the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a magnetic memory element using vertical Ploch lines. FIG. 2 is a diagram showing an information storage section of a magnetic memory element using vertical Ploch lines. FIG. 3 shows a more detailed structure of the vertical Bloch lie/pair. Figure 4 shows how the anisotropic magnetic field (in-plane '0' along the longitudinal direction of the stabilized straight Ploch line) according to the present invention changes in the ion-implanted area and the non-implanted area, and Figure 6 The figure shows how the in-plane anisotropic magnetic field along the longitudinal direction of the stripe domain changes in the ion-implanted part and the non-implanted part, respectively, when the stripe domain is extended in the []]Q] direction. 7 is a diagram showing an embodiment of the present invention. In these figures, 1 is a generator, 2.71 is a minor loose, 3 is a bubble, 4 is a write line transfer gate, and 5 is a read transfer gate. 7 K), 21.41 is the protubo domain wall around the strain domain, 22.23.
Reference numeral 43 indicates the vertical protubo line, numeral 42 indicates the magnetization direction in the Bloch domain wall, 42.72 indicates the mask pattern film pattern at the time of ion implantation, 51 indicates the non-ion inlet, and 52 indicates the ion inlet. There is. O l Enga 2μs + 30 Yoshi 4 glare o ull),
Cノ/2]o CHI) -fltshibaJ (b) ○ [///J -[tto)(C
) 0 (/I/ J --(710 Noo 7 Figure 2 Procedural amendment (own ship!, 9.=t, -4 Commissioner of the Patent Office 1, Indication of the case 1982 Patent application No. 0658
No. 26 No. 2, Title of the invention: Magnetic memory element 3, Relationship to the amended person's case Applicant: 33-1 Shiba 5-chome, 1-ku, Tokyo (423) NEC Corporation Representative: Tadahiro Sekimoto 4, Agent 5-37-8 Shiba, Minato-ku, Tokyo 108 Sumitomo Mita Building ``Linography technology'' should be corrected to ``Photolithography technology.'' 2) In the 2nd and 3rd lines of drawing 5 of the specification, replace the text "Constructs an inner loop. Striped domain head..." with "
Striped domain head that makes up the inner loop -
・” is corrected. 3) In the fourth line of page 5 of the specification, the phrase "on the major line..." is corrected to "on the major line...". 4) In the 15th line of page 5 of the specification, the phrase "The domain wall is dynamically converted..." is corrected to "The domain wall magnetization is dynamically converted...". 5) "S-1 bubble..." on page 9, line 10 of the specification
The statement was corrected to "S-0 bubble...". 6) On page 11, line 7 of the specification, “Magnetic field for static images Hp・-
・" is corrected to "Static in-plane magnetic field Hp...". 7) On page 12, line 19 of the specification, “Magnetic anisotropy field Hk
ip..." is replaced by "anisotropic magnetic field Hkip..."
and correct it. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] The information reading means and the information writing means are equipped with an information storage means, and are made of twinkling perpendiculars created in the protubular domain wall around the stripe tome 4 existing in a ferromagnetic film whose easy magnetization direction is perpendicular to the film surface. 1. A magnetic memory element using a pair of fretsubo lines as a unit of stored information, characterized in that the direction of magnetic anisotropy of the 5-circle is locally changed along a Bloch domain wall.