JPH0738271B2 - Magnetic memory element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a nonvolatile ultra-high density solid-state magnetic memory element.

(Prior Art) This magnetic storage element is provided with an information reading means, an information writing means, and an information storage means, and is a stripe existing in a ferromagnetic material (including a ferrimagnetic material film) whose direction of easy magnetization is perpendicular to the film surface. Adjacent vertical Bloch lines (hereinafter referred to as VBL) created in Bloch domain walls around the domain
And a means for holding and transferring in the Bloch domain wall as a pair. For example, when the element configuration is a major-minor loop configuration, in the major line, the bubble is the information carrier, the minor loop is the stripe domain, and the VBL pair existing in the Bloch domain wall around it is the information carrier. In the flow of information as a whole, first, the information written by the bubble generator (row presence / absence column) moves on the write major line. When one page of information is written on the major line, the information on the major line indicated by the presence or absence of a bubble is transferred to the minor loop in the form of a VBL pair in order to store it in the minor loop. Therefore, the write transfer gate has a function of converting the presence / absence of a bubble into the presence / absence of a VBL pair. The minor loop is composed of Bloch domain walls that can hold VBL pairs. In addition, the minor loop has a function of moving the VBL pair on the stripe domain domain wall to the read transfer gate as necessary. Information transfer from minor loops to read major lines involves the conversion of VBL pairs to bubbles. Read the converted bubble presence / absence column with the bubble detector. Thus, by configuring the minor loop in the stripe domain present in the bubble material, instead of the bubble as the information carrier on the minor loop, by using the VBL pair, compared to the bubble element,
An improvement in storage density of about two digits can be achieved.

In this device, it is an important technique to arrange a large number of magnetic domains at fixed positions on the chip with good stability.

One method to deal with this is to bring the stripe domain domain wall outside the groove thickness boundary film thickness step (Japanese Patent Application No. 60-079658). The reason for this is that if the stripe domain is set so as to include the grooved portion and the outside of the boundary, the film thickness difference at the boundary of the grooved portion causes a demagnetizing field that prevents the domain wall outside the boundary from approaching the film thickness difference portion, This is because the domain wall can respond to the pulsed magnetic field for driving the VBL pair applied from the outside without any damage, and the domain wall response can be reversible. This is a necessary condition for stabilizing the VBL pair holding domain wall. On the other hand, if the stripe domain is confined in the grooved portion, the film thickness step causes a demagnetizing field that strongly suppresses the stripe domain from going out of the grooved boundary. Therefore, the domain wall cannot move freely in response to an externally applied magnetic field. Therefore, it is necessary to initialize the stripe domain so that the stripe domain domain wall is outside the groove thickness boundary film thickness step.

7 (a) and 7 (b) show the main part of the structure. An example of a forming technique for hollowing out a central portion 4 of a region of a domain holding layer 1 on a substrate 2 where a domain is desired to be arranged and arranging a closed domain domain wall to surround it is IE
EE Tran. Magn., MAG-22,784 (1986). However, as a result of experiments, in this method, there is a considerable difference in the magnitude of the bias magnetic field in which the bubble domain changes into the stripe domain between the region where the grooved portions are arranged in parallel and the region where there is no grooved portion, In the trench area, the bias magnetic field must be lower than in other areas,
It turned out that there is a drawback that the domain does not extend. When the bias magnetic field is lowered until the domain extends in the region between the grooves in the region including the grooved portion, it extends in any one of the grooved portion regions and is opposite to the side where the bubble generator 19 is located. As soon as the side, that is, the region where the conductor pattern 20 for domain coupling is present is present, the domain spreads and a stray pattern domain is formed on the front face of the region where the 20 is present. For this reason, the domain which has been extended in the grooved region after the domain which has just been extended cannot be extended to the position where it crosses below the conductor pattern 20 for domain bonding due to the obstructive domain. Therefore,
As shown in FIGS. 8 (a) and 8 (b), an auxiliary groove 7 was provided at the tip of the grooved portion 4 along the longitudinal direction of the groove 4 at a position facing the groove 4. (Japanese Patent Application 61-290887). However, according to this method, once the domain surrounding the groove 4 is stabilized, the domain cannot be pulled out in the direction of the auxiliary groove 7. Therefore, in the region where the auxiliary groove 7 is provided, the read / write operation of the VBL pair cannot be performed and the transfer gate cannot be installed. In FIGS. 7 and 8, 3 is a spacer, 5 is an edge of a hollow portion, and 10 is a bias magnetic field.

(Problems to be Solved by the Invention) The above method is problematic in order to stably arrange a large number of magnetic domains. The present invention eliminates these drawbacks and provides an ultra-high density fixed magnetic memory element capable of simplifying the application condition of an external magnetic field for arranging stripe domains with good stability.

(Means for Solving the Problems) The present invention has a ferromagnetic material (including a ferrimagnetic material) having an information reading means, an information writing means, and an information storage means, and having a direction easy to magnetize in a direction perpendicular to the film surface. In a magnetic memory element having means for holding and transferring a pair of two adjacent vertical Bloch lines formed in the Bloch domain wall at the boundary of the stripe domain existing in the film, in the Bloch domain wall,
A first groove is provided in the stripe domain holding layer in a region where the stripe domain is to be arranged, and a first groove is provided along a longitudinal direction of the first groove in a region facing one tip region. An auxiliary second groove is arranged at a position corresponding to the middle of the adjacent first groove, and the auxiliary second groove is arranged in a region facing the other tip end region of the first groove along the longitudinal direction of the first groove. In the magnetic memory element, a third groove is newly arranged at a position corresponding to the middle of the adjacent first grooves.

A detailed description of the configuration will be given below.

FIG. 1 shows the structure of the main part of the minor loop portion of the stripe domain holding layer in the present invention. FIG. 1 (a) is a main part of the stripe domain holding layer when the method of the present invention is used. Here, the substrate 3 is a spacer, 4, 6, 7
Is a domain retaining layer hollow part, 5 hollow part edge,
10 is a bias magnetic field, 16 is a guide groove, 17 is a conversion gate,
18 is a major line. A groove 4 is formed in a region on the stripe domain holding layer 1 where a domain is desired to be retained, and an auxiliary groove 7 is formed so as to sandwich a region separated along the groove. This can be obtained, for example, by selectively implanting ions such as H ₂ ⁺ into a region corresponding to the grooved portion of the stripe domain holding layer and then etching with hot phosphoric acid. Domain generators and local in-plane magnetic field generating means 8 and 9 are arranged at both ends of the groove 4. 8 and 9
In addition, domains can be generated with good controllability so that the comb-shaped comb eyes shown by 11 in FIG. 2 come to the entrance of the region between the grooves of the groove portion 4, and they are adjacent to each other extending from the groove portion 4. A domain generator of the shape shown in FIG. 6 was used so that the matching domains could be stitched together. In FIG.
12 is the edge of the pattern and 13 is the notch of the pattern.
The feature of the arrangement of the stitching conductor pattern shown in FIG. 9 is that the auxiliary groove is in the notch portion of the conductor pattern 9, and the tip of the auxiliary groove is retracted into the notch as compared with the outlet of the notch. By adopting this structure, when the domains were sewn together, it was possible to eliminate the drawback that a part of the domains sewn together would get caught in the auxiliary groove.

(Operation) The operation of stabilizing the stripe domain will be described with reference to FIGS. 2 to 5. First, the magnetization of the stripe domain holding layer is saturated in the same direction as the magnetization in the domain stabilized around 4 by applying a bias magnetic field. Then, a current in the direction of the arrow is applied to the domain generating section 8 to generate a domain indicated by 11 in FIG. 2 by the magnetic field. To make a domain with such a shape, first 8
It is necessary to design the shape of the generator 8 so that the domains occur along the upper edge 12 of the. An example of the specific shape is FIG. 13 is the notch of the pattern. After that, the absolute value of the bias magnetic field is reduced to allow the domain to pass through the grooved portion as shown in FIG.
Extend to a certain area. After that, a current in the direction of the arrow shown in FIG. 4 is applied to the domain generator 9 to form a domain as shown in FIG. 4 (a). Due to these magnetic fields, the domain 11 is bonded to each other at both ends of the grooved portion, and conversely, the domain surrounded by the closed magnetic domain wall surrounding the grooved portion.
12 are formed. When the externally applied magnetic field is set to zero, the direction is reversed, and the direction of the magnetic field is increased in the direction indicated by 10, the domain having the domain wall surrounding the groove is formed as shown in FIG. Reference numeral 14 is a hollow domain, and 15 is a domain outer domain wall. This domain is used for holding VBL pairs. On the other hand, the domain attached to the auxiliary groove is 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 was still left deep, and a local bias magnetic field due to the conductor current was added to the domain tip. If this is not done, the risk that the tip of the domain will extend due to changes in chip temperature has not been eliminated. Therefore, in the present invention, a groove shown by 16 in FIG. 1 is newly provided, and the potential well around the groove is made shallow to prevent any extension of the domain tip. This groove is the VBL-to-bubble conversion gate unit 1 required for Bloch line memory.
It is also helpful for the domains to extend into the gate 17 in the direction aligned with the longitudinal direction of 4 during the operation of 7. It is sufficient to raise the potential well of the major line 18 only when it is operated by the conductor current magnetic field.

(Example) 4 μm bubble material (YSmLuCa) ₃ on a Gd ₃ Ga ₅ O ₁₂ (111) substrate
A (FeGe) ₅ O ₁₂ garnet film was grown by LPE to a thickness of 2 μm.
Grooves (width 3 μm, arrangement period 12 μm) in the structure of FIG. 1 were formed by selectively ion-implanting the portions to be dug and then etching using phosphoric acid. The resulting groove depth is 2.1μ
It was m. A domain generator having the shape shown in FIG. 6 is placed on top of this by a SiO ₂ spacer of 0.5 μm, and a series of operations starting from the above-mentioned domain generation are performed to close the magnetic field surrounding the grooved portion 4 shown in FIG. Domain 14 with walls could be formed.

(Advantageous Effects of the Invention) By forming an auxiliary grooved portion, it is possible to prevent the potential well from deepening deeply in the domain that extends the stripe domain stabilizing grooved region, and to make The stripe domain can be stably extended along the predetermined position.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a main structure for holding a domain in the present invention, FIG. 2-5 is a diagram showing a domain forming process of the present invention, and FIG. 6 is an example of a domain generator used in the present invention. FIG. 7 is a diagram showing an example of a conventional domain stabilization method having a closed magnetic domain wall surrounding a grooved portion, and FIG. 8 is a diagram showing a conventional example in which an auxiliary groove is provided. In the figure, 1 ... Domain holding layer, 2 ... Substrate, 3 ...
… Spacer, 4 …… Hollowed out domain holding layer, 5 ……
Edge of hollowed part, 6 ... Hollowed part of guard domain holding layer, 7 ... Hollowed part of auxiliary domain holding layer,
8, 9 ... Domain generation conductor pattern, 10 ... Bias magnetic field, 11 ... Magnetic domain generated by domain generator 8, 12 ... Edge of domain generator conductor pattern, 13 ... Domain generation conductor pattern Notch, 14 ...
… Hollowed-out domain, 15 …… Domain outer domain wall, 16 …… Domain 14's extension prevention and guide groove to the gate of domain, 17 …… Conversion gate between Bloch line pair and bubble, 18 …… Major line, 19 ... Bubble generator conductor pattern, 20 ... Domain coupling conductor pattern.

Claims (3)

[Claims] 1. A boundary between stripe domains existing in a ferromagnetic (including ferrimagnetic) film having an information reading means, an information writing means, and an information storage means, and having an easy magnetization direction perpendicular to the film surface. In a magnetic storage element having means for holding and transferring pairs of two adjacent vertical Bloch lines formed in the Bloch domain wall in the Bloch domain wall. Of the first groove is provided, and an auxiliary is provided 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 facing one end region of the first groove. A second groove for use in the first groove is provided, and the second groove for the first groove is disposed at a position corresponding to the middle of the first groove adjacent to the other end region of the first groove along the longitudinal direction of the first groove. Characterized in that a third groove is arranged Magnetic memory element that. 2. The magnetic memory element according to claim 1, further comprising means for generating a domain and generating a local magnetic field in a tip end region of the first groove. 3. The inside of each of the first groove, the second groove, and the third groove is a region where the ferromagnetic layer is completely removed. Alternatively, the magnetic storage element according to the second aspect.