JPH077595B2 - 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 memory element includes an information reading unit, an information writing unit, and an information storage unit, and is present in a ferromagnetic material (including a ferrimagnetic material film) having a direction perpendicular to the film surface as an easy magnetization direction. It has means for holding and transferring, in the Bloch domain wall, pairs of adjacent vertical Bloch lines (hereinafter referred to as VBLs) formed in the Bloch domain wall around the stripe domain. For example, when the element configuration is a major line / minor loop configuration, in the major line, the bubble is an information carrier and the minor loop is a stripe domain,
The VBL pair existing in the Bloch domain wall around it is used as an information carrier. In the flow of information as a whole, first, the information (whether or not there is a bubble) written by the bubble generator moves on the write major line. Because the information for each page is stored in the minor loop in sequence, the minor loop is a Bloch domain wall that can hold the VBL pair so that the information on the major line indicated by the presence of bubbles can be transferred to the minor loop in the form of a VBL pair. The constitution is a feature of the present invention, and is an important key to dramatically improve the storage capacity. By the write line transfer gate, the information (VBL pair) transferred to the minor loop can be moved on the stripe domain domain wall forming the minor loop. Reading from the minor loop, the information transfer to the major line involves the conversion of VBL pairs to bubbles. Read the converted bubble presence / absence column with the bubble detector. In this way, by configuring the minor loop with the stripe domain existing in the bubble material and using the VBL pair instead of the bubble as the information carrier on the minor loop, the storage density can be improved by about two digits compared to the bubble element. Can be achieved.

In this device, it is an important technique to arrange a large number of magnetic domains 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 thereof, the film thickness step at the boundary of the grooved portion causes a demagnetizing field that prevents the domain wall outside the boundary from approaching the film thickness stepped portion. 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, in order to generate a demagnetizing field that prevents the domain wall from approaching this step from the groove step boundary step, the stripe domain domain wall is placed outside the groove step boundary film thickness step section, and the stripe domain is initially set. Must be set.

FIG. 7 (a) shows the main part of the structure. An example of the forming technique for hollowing out the central portion 4 of the region where the domain is to be arranged and arranging the closed domain domain wall so as to surround it is the International Society for Applied Magnetics (Intermag'8) in April 1986.
6) Reported in DD-05. However, in actual practice, with this method, there is a considerable difference in the magnitude of the bias magnetic field at which the bubble domain changes to the stripe domain between the region where the trenches are arranged in parallel and the region where there are no trenches. It was found that the domain does not expand in the partial region unless the bias magnetic field is made lower than in other regions. In the area including the grooved portion, when the bias magnetic field is lowered until the domain extends in the area between the grooves, it extends in any one of the grooved areas and is opposite to the side where the bubble generator 19 is located. On the side, that is, as soon as it comes out to the region where the conductor pattern 20 for domain coupling exists, the domain spreads and a stray pattern domain is formed on the entire region where 20 exists.
For this reason, the domain which has been delayed in the domain which has just been extended and which has been extended in the grooved region cannot be extended to a position where it crosses below the conductor pattern 20 for domain bonding because of being disturbed by the staggered domain.

Another problem is that after stabilizing the domain surrounded by the domain wall on the outside of the grooved portion 4, the tip of the domain is changed from the outside with the variation of the bias magnetic field 10 or the variation of the chip temperature. There was a high probability that it would grow arbitrarily.

(Problems to be Solved by the Present Invention) This method has been a problem in order to arrange a large number of magnetic domains with good stability. An object of the present invention is to provide an ultrahigh-density solid-state magnetic memory element that eliminates these drawbacks and can simplify external application conditions for arranging stripe domains with good stability.

(Means for Solving the Problems) The present invention comprises two VBLs adjacent to each other formed in the Bloch domain wall at the stripe domain boundary existing in the ferromagnetic film having the direction of easy magnetization perpendicular to the film surface. In a magnetic memory element using a VBL pair as a memory carrier, a holding layer is selectively shaved over a region where the stripe domain is to be stabilized to form a groove (first groove), and the groove is centered around the groove. In the method for stabilizing a domain domain wall, an auxiliary groove (second groove) is provided separately from the groove along the longitudinal direction of the groove, and stripe domains are provided on both ends of the stabilizing groove. A domain generator and means for applying a local magnetic field were provided to facilitate the formation of the required domain. The grooved portion (first groove) for stabilizing the stripe domain is arranged along the longitudinal direction on the side not facing the second groove for auxiliary with a region separated from the first groove interposed therebetween. By forming the third grooved portion at a position corresponding to the middle of the first groove, it is possible to prevent the potential well for the domain extending from the grooved region for stabilizing the stripe domain from being suddenly deepened, and to achieve the purpose. The stripe domain can be stably extended to a predetermined position along the longitudinal direction of the grooved portion. A detailed description of the configuration will be given below. FIG. 1 is a configuration diagram of a main portion of a minor loop portion of a stripe domain holding layer according to 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. FIG. 1B is a cross section of the chip taken along the alternate long and short dash line in FIG. A groove 4 is formed in a region on the stripe domain holding layer 1 where a domain is desired to be held, and an auxiliary groove 7 is formed with a region separated along the groove sandwiched therebetween. This is obtained, for example, by etching the grooved portion of the stripe domain holding layer. A domain generator and local in-plane magnetic field generating means 8 and 9 are arranged at both ends of the groove 4.
A domain generator of the shape shown in FIG. 6 was used for 8 and 9 so that the domain of the shape shown by 11 in FIG. 2 could be generated with good controllability. The numbers shown in FIG. 6 are the dimensional ratios of the respective parts.

(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 is applied to the domain generator 8 in the direction of the arrow to generate the domain indicated by 11 in FIG. 2 by the magnetic field. To make a domain with such a shape, first 8
Domains along the upper edge 12 of the
It is necessary to design the shape of the generator 8 so that a domain is generated in the notch 13 when the current of 1 is increased. An example of the specific shape is FIG. After that, the absolute value of the bias magnetic field is decreased, and the domain passes through the grooved portion and extends to the region where the auxiliary groove 7 is present, as shown in FIG. 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 domains 11 are joined to each other at both ends of the grooved portion, and conversely, the domain 14 surrounded by the closed magnetic wall that surrounds the grooved portion is formed. When the externally applied voltage magnetic field is set to zero, the direction is reversed, and the magnetic field strength is increased in the direction indicated by 10, a domain having a domain wall surrounding the groove is formed as shown in FIG. .
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 can be stabilized, but the potential well on the 8 side is still left deep, and the local bias magnetic field due to the conductor current can be added to the domain tip. If this is not done, there is a risk that the tip of the domain may be extended due to temperature change of the chip.

Therefore, in the present invention, a groove 16 is newly provided in FIG.
The potential well around it was made shallow to prevent any extension of the domain tip. This groove also helps the domain to extend into the gate 17 in a direction coinciding with the longitudinal direction of 4 when the Ploch line-to-one bubble conversion gate unit 17 required for the Ploch line memory operates. It is sufficient to raise the potential well of the major line 18 only by the conductor current magnetic field during operation.

(Example) On a Gd ₃ Ga ₅ O ₁₂ (111) substrate, a 4 μm bubble material (YSmLuC
a) A ₃ (FeGe) ₅ O ₁₂ garnet film was grown by LPE to a thickness of 2 μm. The groove of the structure of Fig. 1 is (width 3μm, arrangement period 12μ
m) was formed by selectively ion-implanting a portion to be dug and then etching using a mixed solution of phosphoric acid and sulfuric acid. The depth of the formed groove was 2.1 μm. SiO2 on it
A domain generator having the shape shown in FIG. 6 is arranged through a spacer of 0.5 μm, and a series of operations starting from the above-mentioned domain generation causes a domain 14 having a closed magnetic domain wall surrounding the grooved portion 4 shown in FIG. I was able to form.

(Effect of the Invention) According to the present invention, the stability and reliability of domain arrangement, which has been a problem in the past, is significantly improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a main structure for holding a domain in the present invention, FIGS. 2 to 5 are diagrams showing a domain forming process of the present invention, and FIG. 6 is a diagram showing a domain generator used in the present invention. FIG. 7 is a diagram showing an example, and FIG. 7 is a diagram showing an example of a conventional domain stabilization method having a closed magnetic domain wall surrounding a grooved portion. In the figure, 1. domain retaining layer, 2. substrate, 3. spacer, 4. domain retaining layer hollow portion, 5. hollowed-out edge, 6. guard domain retaining layer hollow portion, 7. auxiliary domain retaining layer hollow portion Part, 8,9. Conductor pattern for domain generation, 10. Bias magnetic field, 11. Magnetic domain generated by domain generator 8, 12. Edge of conductor pattern for domain generator, 1
3.Notch of the domain generating conductor pattern, 14. Hollow-out domain, 15. Domain outer domain wall, 16. Domain 14 extension prevention and groove for guiding the gate of the domain, 17.
Conversion gate between Bloch line pair and bubble, 18. Major line, 19. Conductor pattern for bubble domain generator, 20. Conductor pattern for domain coupling.

Claims (1)

[Claims] 1. A stripe domain existing in a ferromagnetic (including ferrimagnetic) film 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 device having a means for holding and transferring a pair of two adjacent vertical Bloch lines formed in a boundary Bloch domain wall in the Bloch domain wall, a stripe domain holding is performed over a region where a stripe domain is desired to be arranged. The layer is provided with a first groove, and the auxiliary second groove is arranged in a region separated from the first groove formation region along the longitudinal direction of the first groove, and the auxiliary groove is provided. Of the first groove on the side of the first groove on the side not facing the second groove, the third groove is newly formed at a position corresponding to the middle of the first grooves adjacent to each other along the longitudinal direction of the first groove. Groove, and place it in the tip region of the first groove. Magnetic memory device characterized in that it comprises means in development and local magnetic field generator.