JPH01220288A - Magnetic storage element - Google Patents

Abstract

PURPOSE:To obtain a solid-state magnetic storage element with ultra-high density capable of simplifying the impression condition of an external magnetic field for arranging a stripe domain with high stability by arranging an auxiliary second groove at a position equivalent to the intermediate part of a first groove, and setting the width of the second groove less than that of the first groove. CONSTITUTION:The formation of a prescribed domain is performed easily by forming the groove 4 (first groove) by cutting a holding layer 1 selectively extending over an area desired to stabilize the stripe domain, stabilizing a domain magnetic wall in the periphery centering on the groove, providing an auxiliary groove 7 (second groove) at the position equivalent to the intermediate part of the first groove in the area separated from the forming area of the groove 4, and supplying a domain generator and a local magnetic impression means to both ends of the groove for stabilizing the stripe domain. Furthermore, a fact that a potential well for a domain growing steely from a groove digging area for stabilizing the stripe domain is suddenly deepened is prevented from being generated by generating an auxiliary groove digging part, and the width of the second groove 7 is set less than that of the groove 4. In such a way, it is possible to obtain the solid-state magnetic storage element with ultra-high density in which a large number of stripe domains can be arranged stably.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a nonvolatile ultra-high density solid state magnetic memory element.

(Prior art) This magnetic memory element includes an information reading means, an information writing means, and an information storage means, and has a stripe existing in a ferromagnetic material (including a ferrimagnetic film) whose easy magnetization direction is perpendicular to the film surface. It has means for holding and transferring adjacent vertical Bloch lines (hereinafter referred to as VBL) formed in the Bloch domain wall around the domain as a pair within the Bloch domain wall. For example, when the element configuration is a Major-minal loop configuration, in the Major line, bubbles are used as information carriers, minor loops are configured with striped domains, and VBL pairs existing in the Bloch domain wall around the bubbles are used as information carriers. To show the overall flow of information, first, the information written by the bubble generator (column of bubble presence/absence) moves along the write major line. When one page of information is written on the major line, in order to store it in the minor loop, the information on the major line indicated by the presence or absence of bubbles is transferred to the minor loop in the form of a VBL pair. Therefore, the write transfer gate has a function of converting the presence or absence of a bubble into the presence or absence of a VBL pair. The minor lube is composed of Bloch domain walls that can hold VBL pairs. Furthermore, the minor lube has a function of moving the VBL pair of the striped domain domain wall to the readout transfer gate as necessary. Information transfer from the minor loop to the read major line involves converting VBL pairs to bubbles. The bubble detector reads the converted bubble presence/absence column. in this way,
By constructing the minor lube with striped domains present in a bubble material and using VBL pairs instead of bubbles as information carriers on the minor lube, an improvement in storage density of about two orders of magnitude compared to bubble elements can be achieved.

In this device, an important technique is to stably arrange a large number of magnetic domains at predetermined positions on the chip.

One way to deal with this is to move the stripe domain domain wall to the outside of the trench boundary boundary film thickness step (Japanese Patent Application No. 6O-079658). The reason for this is that when a stripe domain is set to include the trench and the outside of its boundary, the film thickness step at the trench boundary creates a demagnetizing field that prevents the domain wall outside the boundary from approaching the film thickness step. This is because the magnetic domain wall can respond without interference to a pulsed magnetic field for driving the VBL pair applied from the outside, and the response of the magnetic domain wall can be reversible. This is a necessary condition for stabilizing the VBL pair-holding domain wall. On the other hand, when striped domains are confined within the grooved portion, the difference in film thickness generates a demagnetizing field that strongly suppresses the striped domains from moving outside the grooved boundary. Therefore, the domain wall cannot freely move in response to an externally applied magnetic field. Therefore, it is necessary to initially set the stripe domain so that the stripe domain domain wall is located outside the trench boundary boundary film thickness step part.

The main parts of the structure are shown in FIGS. 7(a) and 7(b).

An example of a formation technique for hollowing out the center 4 of the region in the domain holding layer 1 on the substrate 2 where the domain is desired and arranging a closed domain domain wall so as to surround it is I.
IEEE Transactions on Magnetics (IEEE Tran, Magn, MAG)
-22, 784 (1986)). However, experiments have shown that with this method, there is a considerable difference in the magnitude of the bias magnetic field that changes a bubble domain into a stripe domain between a region where the trenches are lined up in parallel and a region where there are no trenches. It has been found that the domain does not elongate unless the bias magnetic field is lower in the trench region than in other regions. When the bias magnetic field is lowered until the domain extends in the region between the grooves in the region including the grooved portions, it extends in one of the grooved portions and forms the side where the bubble generator 19 is located. As soon as it appears on the opposite side, that is, in the area where the conductor pattern 20 for domain coupling is located, the domain expands, and a stray pattern domain is formed in front of the area where the conductor pattern 20 is located. For this reason, the domain that has been extending through the grooved region later than the domain that has just extended is obstructed by the stray domain and cannot extend to the point where it crosses under the conductor pattern 20 for domain joining. Therefore,
As shown in FIGS. 8(a) and 8(b), an auxiliary groove 7 is provided at the tip of the grooved portion 4 at a position corresponding to the middle of adjacent grooves 4 along the longitudinal direction of the groove 4. (Patent Application No. 62-208)
712). However, when experimenting with this method,
The domains that have extended between the grooves 4 tend to spread laterally in the front area of the conductor pattern 9 that is not sandwiched between the grooves.
It was difficult for the plurality of domains to simultaneously reenter the region between the grooves (auxiliary grooves 4) and expand. Note that 16 is a guide groove, 17 is a conversion gate, and 18 is a major line.

(Problems to be Solved by the Present Invention) The above-mentioned method has been problematic in order to stably arrange a large number of magnetic domains. An object of the present invention is to provide an ultra-high-density solid-state magnetic memory element that eliminates these drawbacks and can simplify the conditions for applying an external magnetic field for stably arranging striped domains.

(Means for Solving the Problems) The present invention provides a VBL consisting of two adjacent VBLs created in a Bloch domain wall at a stripe domain boundary existing in a ferromagnetic film whose easy magnetization direction is perpendicular to the film surface. In a magnetic memory element that uses a pair of striped domains as a storage carrier, a groove (first groove) is created by selectively scraping the retention layer over a region where the striped domain is desired to be stabilized, and a domain magnet is formed around the groove as a center. In the structure for stabilizing the wall, an auxiliary groove (second groove) is provided in a region of one tip of the political condition along the longitudinal direction of the political condition in a region separated from the groove forming region, and a striped domain is provided. Domain generators and local magnetic field application means were provided at both ends of the stabilizing groove to facilitate the formation of the desired domains. By creating the auxiliary trench, the potential well for the domain extending out of the striped domain stabilizing trench can be prevented from becoming suddenly deeper, and the width of the second trench can be made smaller than the first trench. By making the width smaller than the width of , it became possible to stably extend the stripe domain to a predetermined position along the longitudinal direction of the intended groove digging.

(Example) A detailed explanation of the configuration example will be given below.

FIG. 1 shows the structure of the main part of the minor loop portion of the striped domain holding layer in the present invention. Figure 1 (a), (
b) is the main part of the striped domain retention layer when using the method of the present invention. A groove 4 (first groove) is formed in a region on the striped domain holding layer 1 where a domain is to be held, and an auxiliary groove 7 (second groove) is formed between regions separated along this groove. This can be obtained, for example, by selectively implanting ions such as H2+ into the region corresponding to the grooved portion of the striped domain holding layer, and then etching with hot phosphoric acid. A domain generator and local in-plane magnetic field generating means 8 and 9 are arranged at both ends of the groove 4. In addition, in 8.9, the comb-shaped comb eye shown by 11 in FIG. 2 is placed at the entrance of the area between each groove of the groove part 4.
A domain generator having the shape shown in FIG. 6 was used so that domains could be generated with good controllability and adjacent domains extending from the groove 4 could be sewn together. The arrangement of the conductor pattern for sewing shown in FIG. 19 is characterized in that the auxiliary groove is located at the notch portion of the conductor pattern 9, and the tip of the auxiliary groove is recessed into the notch compared to the outlet of the notch. By adopting this structure, it was possible to eliminate the drawback that when domains were sewn together, a portion of the sewn domains would get caught in the auxiliary groove.

The operation of stripe domain stabilization will be explained using Figures 2 (a) and (b) to Figures 5 (a) and (b). First, the magnetization of the stripe domain holding layer is changed to 4 by applying a bias magnetic field. The magnetization is saturated in the same direction as the magnetization in the domain that is stabilized around .Then, a current is applied to the domain generator 8 in the direction of the arrow, and the magnetic field generates the domain shown at 11 in Fig. 2. In order to create a domain with a similar shape, it is first necessary to design the shape of the generator 8 so that the domain is generated along the upper edge 12 of the generator 8. An example of a specific shape is shown in FIG. Thereafter, the absolute value of the bias magnetic field is decreased, and the domain extends past the grooved part to the area where the auxiliary groove 7 is located, as shown in FIG. Applying a current in the direction of the arrow shown in the figure, Figure 4 (a
) to form a domain as shown in Due to these magnetic fields, the domains 11 are joined to each other at both ends of the grooved portion, and conversely, a domain 12 surrounded by a closed domain wall surrounding the grooved portion is formed. When the externally applied magnetic field is reduced to zero, and then its direction is reversed to the direction indicated by 10 and the strength of the magnetic field is increased, a domain with domain walls surrounding the groove is formed as shown in FIG. 5. This domain is used for VBL pair maintenance. On the other hand, the domains attached to the auxiliary grooves are completely erased by this change in the bias magnetic field.

In this way, the domain surrounded by the domain wall surrounding 4 was stabilized, but the potential well on the 8 side remained deep, and a local bias magnetic field due to the conductor current was applied to the domain tip. If this is not done, there is a risk that the domain tips will extend due to changes in chip temperature, etc. Therefore, in the present invention, a groove (third groove) shown at 16 in FIG. 1 is newly provided, and the potential well around the groove is made shallow to prevent the domain tip from extending arbitrarily. This groove is the V required for Bloch line memory.
It also helps that the domains extend into the gate 17 in an orientation consistent with the longitudinal direction of 4 when the BL-to-bubble conversion gate section 17 operates. The potential well of major line 18 is only activated by the conductor current magnetic field.
It is enough to raise it.

A 411m bubble material (Y?SmLuCa)3(FeGe)501□garnet film was grown on a Gd5Ga5002(111) substrate to a thickness of 2 pm by LPE. Grooves in the structure shown in Figure 1 (width of groove 4 3 μm, width of groove 7 211 m, arrangement period 1)
2pm) was formed by selectively implanting ions into the area where a groove was to be dug, and then etching using phosphoric acid. The depth of the resulting trench was 2.111 m. On top of that, 5102
A domain generator having the shape shown in FIG. 6 is arranged via a spacer of 0.5 pm, and a series of operations starting from the above-mentioned domain generation is performed to form the trench portion 4 shown in FIGS. 5(a) and 5(b). A domain 14 having a closed domain wall surrounding the domain 14 was formed.

(Effects of the Invention) As described above, according to the present invention, a large number of striped domains can be stably arranged.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams showing examples of main structures for holding domains in the present invention, and Figures 2 (a) and (b).
) to FIGS. 5(a) and 5(b) are diagrams showing the domain formation process of the present invention. FIG. 6 is a diagram showing an example of a domain generator used in the present invention, FIG. 7(a), (b) and FIG.
Figures a) and (b) each show an example of a conventional domain stabilization method in which a closed domain wall surrounds a grooved portion. In the figure, 1. domain retention layer, 2. Substrate, 3. Spacer, 4. Domain holding layer hollowed out part (first groove), 5
, Hollowed edge, 6. Guard domain holding layer hollowed out part, 7. Auxiliary domain holding layer hollowed out part (second
groove), 8, 9. Conductor button for domain generation, 10° bias magnetic field, 11. magnetic domains generated by domain generator 8; 12. Edge of conductor pattern for domain generator, 13. Notch of conductor button for domain generation, 14.
Hollow domain, 15. Domain outer peripheral domain wall, 16, groove for preventing extension of the domain 14 and guiding the domain to the gate portion (third groove), 17. Conversion gate between Bloch line pair and bubble, 18. Major Line, 19
．． Conductor pattern for bubble generator, 20. This is a conductor pattern for domain coupling.

Claims (1)

[Claims] (1) Bloch 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 having a means for retaining and transferring a pair of two adjacent vertical Bloch lines formed in a domain wall within a Bloch domain wall, a first groove is formed in a stripe domain retention layer in a region where a stripe domain is to be arranged. is provided, and an auxiliary groove is provided at a position corresponding to the middle of each adjacent first groove along the longitudinal direction of the first groove in a region facing one of the tip end regions of the first groove. A third groove is arranged at a position corresponding to the middle of the first grooves adjacent to each other along the longitudinal direction of the first groove in a region opposite to the other tip region of the first groove. place,
A magnetic memory element characterized in that the width of the second groove is smaller than the width of the first groove.