JPS62124691A - Magnetic memory element - Google Patents

Abstract

PURPOSE:To eliminate the ununiformity of potential well of magnetic domain walls at the time of stabilizing stripe domain by forming a vertical magnetized film having high saturation magnetization and high anti-magnetism on the surface of a magnetic film. CONSTITUTION:A stripe domain holding layer 1 is attached on a substrate 1. A vertical magnetized film having high saturation magnetization and high anti-magnetism is formed on the holding layer 1 in an area excepting the area in which annular stripe domain is to be held to make direction of magnetization opposite to the stripe domain. Necessary thickness of the vertical magnetized film 19 can be made thin by using material that makes the saturation magnetization of the vertical magnetization larger than the saturation magnetization of the annular domain holding layer. Thus, the ununiformity of potential well of magnetic domain walls at the time of stabilizing the stripe domain can be eliminated and the reliability of a flopholine memory is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to nonvolatile ultra-high density solid state magnetic storage elements.

(Prior Art) Development of magnetic bubble elements is actively being carried out in various places, focusing on high-density solid-state magnetic memory elements. However, with currently used garnet materials, the minimum attainable bubble diameter 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 garnet material.

This is not easy and is even considered to be the limit of bubble density.

We have developed an ultra-high-density magnetic memory element that is magnetized in the direction perpendicular to the film surface, which can significantly improve the density limit based on the characteristics of the bubble retention layer, and at the same time maintain the information readout time at the same level as conventional elements. A Bloch line pair (hereinafter referred to as a Bloch line pair) consists of two vertical Bloch lines that statically and stably exist within a Bloch domain wall that is the boundary of a stripe domain formed in a ferromagnetic (including ferrimagnetic) film with easy direction. VBL
It is called a pair. ) was invented as a storage unit. (Japanese Patent Application No. 57-182346) The present magnetic memory element includes information reading means, information writing means, and information storage means, and also has means for transferring the VBL pair within the Bloch domain wall.

One of the most important parts of this device is the information storage section (hereinafter referred to as the minor loop).

In such a magnetic memory element, it is essential to stably hold the VBL pair of striped domain domain walls written as information and to be able to selectively transfer one bit at a time. As a method of maintaining stability, the patent application 1982-
As described in 065826, the direction of magnetic anisotropy in the film plane is locally changed along the Bloch domain wall around the striped domain that constitutes the minor loop.6 Then, along the striped domain domain wall, It is possible to create positions where VBL pairs stably exist and positions where they do not.

Regarding the selective transfer of each bit of the VBL pair, which is another condition, in principle, means is required to apply a force to drive the VBL pair along the domain wall. In reality, a method is to apply a local in-plane magnetic field in the form of a traveling wave along the domain wall surface to the VBL pair existence region, and a pulse bias magnetic field is applied to the stripe domain domain wall to dynamically move the domain wall. It has been considered to utilize gyroscopic force, which is one of the reactions that occur at the position of There's a problem. On the other hand, in the latter case, the domain wall and driving force provided by the externally applied pulse bias magnetic field are very important. In order to make this domain wall driving force constant at each part on the chip, it is important to determine how to stabilize the stripe domain, that is, to optimize the potential well shape of the stripe domain domain wall.

Conventionally, this method involves hollowing out a region in the striped domain holding layer 1 in which the striped domain 6 is to be stabilized, as shown in FIG. A region with magnetization 8 in the opposite direction to the bias magnetic field 10 is created at the periphery of the hollowed out part by embedding the perpendicularly magnetized material 19 and using the magnetic field leaking outward from that part, and the domain wall 7 around the outside thereof is made into a minor loop. It was used as a drive domain domain wall.

Alternatively, as shown in FIG. 4, this can be achieved by selectively digging grooves to form grooves 3 only in the portions of the striped domain holding layer 1 where it is desired to hold the striped domains 6 in a ring shape.

Among the boundaries of the groove, the boundary 24 has a convex portion on the inside thereof, which serves to attract the inner domain wall of the striped domain 6 to the boundary 24, and the boundary 25 serves to attract the inner domain wall of the striped domain 6 to 24. It serves as a guide to prevent the inner domain wall from being too far away from 24. Furthermore, the width of the convex portion having 24 boundaries is the natural width W of the stripe domain. It is necessary to keep it above.

If this is not done, when the striped domain 6 is held in a ring shape in the groove, the repulsive interaction between the linear domains on both sides of the convex part with the boundary 24 will become strong, and the inner domain wall of the ring-shaped striped domain will become strong. is no longer firmly fixed directly below the boundary 24. groove 2 to satisfy the above conditions.
3, the stripe domain is fixed in a ring shape with the groove boundary 24 as the inner diameter as shown in FIG.

When the striped domain is maintained in this way, the profile in the normal direction of the domain wall surface of the potential well of the domain wall outside the ring-shaped domain (domain wall existing away from the boundary 24) is mainly due to the demagnetizing field effect determined by the width of the striped domain. This eliminates the influence of fine unevenness at the boundary of the trench.

When an externally applied pulsed bias magnetic field is applied to such a domain wall, the domain wall is driven uniformly over the entire domain wall 7. Therefore, when the information stored in the domain wall in the form of the presence or absence of the VBL pair is moved using the gyroscopic force generated on the VBL pair by applying the pulse bypass magnetic field 10, the amount of movement is controlled by the shape of the pulse bias magnetic field. It becomes easier.

In the figure, numerals 8 and 9 indicate the directions of magnetization inside and outside the domain, respectively.

(Problem to be solved by the invention) Among these stripe domain retention methods, the method of hollowing out the stripe domain retention layer and embedding a perpendicular magnetization film having high saturation magnetization and high coercive force in the hollowed out part is Embedding the perpendicularly magnetized material was technically difficult and posed a manufacturing problem.

Furthermore, in order to retain the stripes in a ring shape, the method of selectively digging grooves in the area where the ring-shaped stripe domains exist requires that the depth of the grooves be at least 5% of the stripe domain retaining layer. Due to the film thickness difference at the boundary,
Difficulties have arisen in the process of forming conductor patterns and insulating layers for the stripe domain formation operation, Bloch line pair transfer, or gate function, which are laminated on the stripe domain holding layer.

The purpose of the present invention is to eliminate such conventional drawbacks, and to apply VBJ to striped domain domain wall soil with minor looseness.
The object of the present invention is to provide an ultra-high density storage element that uses VBL pairs as information units, which can stably hold the pairs and selectively transfer one bit at a time.

(Means for solving the problem) Storing VBL pairs consisting of two adjacent VBLs created in the Bloch domain wall at the stripe domain boundary existing in a ferromagnetic film whose easy magnetization direction is perpendicular to the film surface. In the magnetic memory element used as a unit, a perpendicularly magnetized film having high saturation magnetization and high coercive force is provided on the surface of the stripe domain holding layer except for the region where the ring-shaped stripe domains exist, and the direction of the magnetization is By forming the magnetization direction opposite to the magnetization direction of the stripe domains, the ring-shaped stripe domains can be maintained without the manufacturing problems that have conventionally occurred.

A striped domain holding layer 1 is provided on a substrate 2 shown in FIG. 1(a). A perpendicularly magnetized film having high saturation magnetization and high coercive force is formed thereon in a region other than the region in which the ring-shaped stripe domain is desired to be maintained, so that the direction of magnetization is opposite to that of the stripe domain. Perpendicular magnetization film 19
By using a material in which the saturation magnetization of the perpendicularly magnetized film is larger than that of the ring-shaped domain retention layer, the required film thickness can be made thinner, and a large step difference can be avoided in the conductor process to be formed on the retention layer. Problems can be solved.

The width of the ring-shaped region in which no perpendicular magnetization film is formed is larger than the natural width W of the ring-shaped domain, and is about 2w or less.

The inner domain wall of the striped domain 6 is attracted to the boundary 4 of the perpendicularly magnetized film. The outer boundary 5 of the perpendicular magnetization film serves as a guide to prevent the inner domain wall from being too far away from the stripe domain 4 when initially setting the stripe domain 6.

Of course, when the width of the island region of the perpendicularly magnetized film surrounded by the region where no ring-shaped perpendicularly magnetized film is formed is set to W0 or more, but also when it is set to W or less, the inner domain wall of the ring-shaped domain is It was possible to hold it at the end of the island-like perpendicularly magnetized film.

This is considered to be because the perpendicularly magnetized film with high saturation magnetization absorbs the interaction between the opposing ring-shaped domains.

As shown in FIG. 1(b), the stripe domain is fixed in a ring shape having the perpendicular magnetization film boundary 4 as its inner diameter.

In this way, when a ring-shaped striped domain is held with its inner domain wall at the end 4 of the island-like region of the island-like perpendicularly magnetized film, the potential of the outer domain wall (domain wall existing away from the boundary 4) of the ring-shaped domain is mainly This is determined by the demagnetizing field effect determined by the stripe domain width, and can reduce the influence of non-uniformity that may occur at the end of the island-like region of the perpendicularly magnetized film.

When an externally applied pulsed bias magnetic field is applied to such a domain wall, the domain wall movement becomes uniform over the entire domain wall 7.

Therefore, when the information stored in the domain wall in the form of the presence or absence of the VBL pair is moved using the gyroscopic force generated on the VBL pair by applying the pulse bias magnetic field 10, the amount of movement is controlled by the shape of the pulse bias magnetic field. It becomes easier.

In the figure, numerals 8 and 9 indicate the directions of magnetization inside and outside the domain, respectively.

Examples are shown below.

Figure 2 shows the process of forming striped domains into a ring shape, and the process of converting information stored in VBL pairs within the striped domain magnetic wall, which is a necessary condition for this device, into bubble domains when reading or writing. A specific operation process for an example of the shape of a perpendicular magnetization film pattern including a gate portion 18 for performing the function of storing data expressed in the form of the presence or absence of bubbles in the major line 17 in the form of VBL pairs within the stripe domain magnetic wall. shows. A bubble generator consisting of a conductive pattern 12 is placed at the tip 11 of the region 3 where no perpendicular magnetization film is formed. In advance, apply a magnetic field in the same direction as the bias magnetic field 10 to the entire effective chip surface to make the entire effective chip surface 10
Keep it saturated in the direction of. After that, an appropriate bias magnetic field Hz is applied.

Thereafter, when a pulsed current 13 of the shape shown is applied to this bubble generator, it generates bubbles at 11, which form striped domains extending along the region 3, each with its apex facing the introduction guide 14, 14'. It will form a U-shape. For such a stripe domain number, a pulse current 16 is applied to the conductor pattern 15 in the direction of the arrow, and the portion extending into the stripe domain 14 and 14' in the area between the two conductor patterns is Connect the part that stretches inside. The bonded stripe domains contract under the action of the bias magnetic field Hz and the domain wall surface tension that tries to minimize the surface energy of the domain walls, and eventually the boundary 4 of the perpendicularly magnetized film region as shown in Fig. 1 is It becomes a ring-shaped striped domain with a border. A VBL pair, which is an information carrier, is written on the outer peripheral domain wall 7 of this domain 6. Grooves 18 and 181 are for gates connecting major lines 17 and 17', which represent information in the form of bubbles necessary for Bloch line memory, and ring-shaped stripe domain sections that store information in the form of presence or absence of VBL pairs. belongs to. Note that the thickness of the perpendicular magnetization film was actually evaluated in the range of 0.5% to 10% of the total film thickness of the striped domain holding layer, and there was no problem with the formation of ring-shaped striped domains.

(Effects of the Invention) The present invention eliminates the need to embed perpendicular magnetization material, which has been a problem in the past, and allows conductor patterns, etc. to be laminated on top of the striped domain retention layer through grooves with a depth of 5% or more. By forming a perpendicularly magnetized film with a thickness of about 1% of the holding layer, it is possible to reduce the step difference, which was a problem during the stacking process, and improve the stability of the stripe domain. It became possible to remove the inhomogeneity of the potential well in the domain wall region of the domain wall, increasing the stability of Bloch line pair transfer and thus improving the reliability of Bloch line memory.

Furthermore, the distance between the opposing inner domain walls of the ring-shaped domains could be made closer than before, making it possible to achieve higher density.

[Brief explanation of drawings]

FIGS. 1(a) and (b)% FIG. 2 is a diagram showing an example of the structure of the stripe domain holding layer of the present invention, and FIGS. 3 and 4 are diagrams showing a conventional example. In the figure, 1: varnish drive domain holding layer, 2: substrate, 3: region where no perpendicular magnetization film is formed, 4: island-like perpendicular magnetization film boundary, 5:
Perpendicular magnetization film outer boundary, 6: ring-shaped stripe domain, 7: stripe domain outer peripheral domain wall, 8 inner magnetization direction of two domains, 9 outer magnetization direction of two domains, 10: bias magnetic field direction. 11: Tip of grooved part (bubble generating part), 12: Bubble generator conductor pattern, 13: Bubble generating current, 14.1
4' Varnish drive domain tip introduction guide, 15 Conductor pattern for varnish drive domain fusion, 16: Stripe domain fusion current. 17.17': Major line (bubble transfer path). 18.18': ) Lance 7 agate part (grooving part)
. 19: Hard magnetic perpendicular magnetization material), 20: Magnetization direction of hard magnetic perpendicular magnetization film (material). 23: Grooving part, 24: Inner boundary of trenching part, 25 and a half
1 Figure (b)! , Nu Y Life ゛ To Main Hosho F42, λ (2nd Stryg F Main 7, Zu) Quib Domain Dok) Shufu Gokabe 8, Nu Y Life F Main Meya Soi L Sakyumi Sa 9 Zu Y Live Domain no Tato ,? Ode restoration q stone scolding 1. 10. Set bias 2 to 1. R, Z * Mi Ishisaji! ! : Mute, Hz, Kakashi Saito 20,
Hard stone sa name 7 direct magnetization raft training 1 moderation test k. Tei 4 Diagram z3 (Moj straight weight part 6 Ringe °-shaped strip Y live ° Nuin 7, stripe): Main ct surrounding stone handling wall 8 Domain M
J Eikakasei Yumisa

Claims (1)

[Claims] In a Bloch domain wall at the boundary of a stripe domain existing in a ferromagnetic (including ferrimagnetic) film that has information reading means, information writing means, and information storage means and whose easy magnetization direction is perpendicular to the film surface. In a magnetic memory element that uses a vertical Bloch line pair consisting of two adjacent vertical Bloch lines created in 1 as a storage information unit, and has means for transferring the vertical Bloch line pair within a Bloch domain wall, A magnetic memory element characterized in that a perpendicularly magnetized film having high saturation magnetization and high coercive force is selectively formed, and a ring-shaped stripe domain is maintained in a region where the film is not formed.