JPH0782745B2 - Magnetic memory element - Google Patents

Description

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

(Problems to be solved by the prior art and the invention) Phases formed in a Bloch domain wall around a stripe domain present in a ferromagnetic film (including a ferrimagnetic material) whose direction of magnetization is perpendicular to the film surface. VBL consisting of two adjacent VBLs
In a magnetic memory element using a pair as a memory unit, a groove is selectively formed on the surface of the stripe domain holding layer over a region to be stabilized,
The stripe domains were stabilized in the groove in the form of ring stripe domains.

A detailed description of the configuration will be given.

On the surface of the stripe domain holding layer 1 shown in FIG. 4, only the portion where the stripe domain is to be held in a ring shape is selectively dug to form a groove 3. This width is the natural width W ₀ of the stripe domain (state without magnetic field). Width) and 2W
_{It is} about ₀ or less. The reason for this is that if the groove is too narrow, the domain will not grow stably in the groove. If it is too wide, the domains will escape from the inner membrane pressure step boundary,
There is another domain in the groove. Within the boundaries of the groove,
Since the boundary 4 has a convex portion inside thereof, it serves to attract the inside magnetic domain wall of the ring-shaped stripe domain 6 to 4, and when the boundary 20 initializes the ring-shaped striped domain 6, the inner domain wall is not much from 4. It acts as a guide to keep you away. Furthermore, 4
The width of the convex part with the boundary of must be W ₀ or more.
If this is not done, when the ring-shaped stripe domain 6 is held in the groove, the repulsive interaction between the linear domains on both sides of the convex portion having the boundary 4 becomes strong, and the inner domain wall of the ring-shaped stripe main becomes the boundary. 4 It will not be fixed right underneath. When the groove 3 is formed so as to satisfy the above conditions, the stripe domain is fixed in a ring shape having an inner diameter of the groove boundary 4 as shown by 6 in FIG.

When the stripe domain is held in this way, the domain wall outside the ring domain (domain wall existing away from the boundary 4)
The potential well in the portion is determined mainly by the demagnetizing effect which is determined by the stripe domain width, and is not affected by the minute unevenness of the finish of the groove boundary. When the externally applied pulse bias magnetic field is applied to such a domain wall, the domain wall movement becomes uniform over the entire domain wall 7. Therefore, a pulse bias magnetic field is applied in the same direction as the static bias magnetic field 17 for holding the domain, information stored in the domain wall in the presence or absence of the VBL pair, and the VBL pair is moved by utilizing the gyro force generated. At that time, it becomes easy to control the movement amount by the shape of the pulse bias magnetic field. In the figure, 8 and 9 are the directions of magnetization inside and outside the domain, respectively. However, in this method, since the effect of attracting the magnetic domain walls of the film thickness step boundary 4 and the film thickness step boundary 20 is the same, the inner domain wall of the ring-shaped domain often deviates from the boundary 4 depending on the degree of step formation, On the contrary, the outer wall may be attracted to the boundary 20. Examples of the transfer gate portion indicated by 13 in FIG. 4 are shown in Japanese Patent Application Nos. 60-089321 and 61-002399.

The present invention eliminates such a conventional defect and stably holds the VBL pair on the stripe domain domain wall, which is a minor loop, and enables selective transfer bit by bit.
An object of the present invention is to provide an ultra-high density magnetic memory element using a pair as an information unit.

(Means for Solving Problems) In the present invention, in a Bloch domain wall at the boundary of ring-shaped stripe domains formed in a ferromagnetic film (including a ferrimagnetic film) whose direction of magnetization is perpendicular to the film surface In a magnetic memory element using as a memory unit a VBL pair made up of two adjacent VBLs made in step 1, a ring-shaped first
And a second groove deeper than the ring-shaped first groove is provided on the outer peripheral portion of the ring-shaped groove, and the ring-shaped stripe domain is in the ring-shaped first groove-shaped portion. And a structure in which a third groove trench having the width of the domain wall is provided at the inner boundary of the ring-shaped first groove in the above structure. It is an element.

(Operation) According to the present invention, by adopting the above-mentioned structure, the surface of the stripe domain holding layer of the prior art is selectively grooved over a region in which the stripe domain is desired to be stabilized, and the stripe domain is formed in the groove. The problem that the domain was easy to separate from the inner step boundary of the groove in the structure stabilized in the shape of a striped domain was solved, and the problem of initial setting of the stripe domain for minor loops was solved. A detailed description of the configuration will be given below.

The surface of the stripe domain holding layer 1 shown in FIG. 1 is selectively dug only in the portion where the stripe domain is to be held in a ring shape, and the groove 3 is formed. This width is larger than the natural width W ₀ of the stripe domain (width without magnetic field) and is 2W ₀
The level is below. The reason for this is that if the groove is too narrow, the domain will not extend stably in the groove. If it is too wide, the domains will escape from the inner boundary of the film thickness step,
Another domain enters the groove. Within the boundaries of the groove,
Since the boundary 4 has a convex portion inside thereof, the boundary 4 serves as a guide for preventing the inner side wall of the stripe domain 6 from being too far from the boundary 4. Unlike the conventional case, the outer side of the boundary 5 is further dug, so that the boundary 5 does not bring the ring-shaped stripe domain 6 close to the boundary 5, but rather generates an effective magnetic field that presses the boundary 5 against the boundary 5.
To prevent the outer domain walls of the domain from approaching. The boundary 5 in the conventional device (the boundary indicated by 20 in FIG. 4) had a property of attracting the outer domain wall of the domain. The width of the convex portion having the boundary of 4 needs to be W ₀ or more. If this is not done, when the stripe domain 6 is held in the groove in a ring shape, the repulsive interaction between the linear domains on both sides of the convex portion having the boundary 4 is strengthened, and the inner domain wall of the stripe domain on the ring is It will no longer be fixed directly under border 4. The width of this convex portion can be made narrower than that of the conventional single groove digging method. When the groove 3 of the stripe domain stabilizing region is formed by the above method, the stripe domain is fixed in a ring shape having an inner diameter of the groove boundary 4 as shown by 6 in FIG.

When the stripe domain is held in this way, the domain wall outside the ring domain (domain wall existing away from the boundary 4)
The potential well of the portion is determined mainly by the demagnetizing effect which is determined by the stripe domain width, and is not affected by the magnetic unevenness at the boundary of the trench. When the externally applied pulse bias magnetic field is applied to such a domain wall, the domain wall movement becomes uniform over the entire domain wall 7. Therefore, when moving the information stored in the domain wall in the presence or absence of the VBL pair using the gyroscopic force generated in the VBL pair by the pulse bias magnetic field applied in the same direction as the domain holding static bias magnetic field 17, It becomes easy to control the movement amount by the pulse bias magnetic field shape. In the figure, 8 and 9 are the directions of magnetization inside and outside the domain, respectively.

Further, as shown by 19 in FIG. 3 on the outer periphery of the film thickness step boundary 4 (the surface of the groove portion 3), when a groove having a width of about the domain wall is formed, a ring-shaped domain is further stabilized just below the film thickness step boundary 4. It can be fixed easily.

Example 1 An example will be described below. The process of forming the stripe domain in a ring shape using Fig. 1 is converted into the bubble domain when reading the information stored in the VBL pair in the stripe domain domain wall, which is a necessary condition for this device. , Or an example of a grooved pattern shape including the gate portion 13 for performing the function of storing the data represented by the presence or absence of bubbles in the major line 16 in the stripe domain domain wall at the time of writing, as a VBL pair A specific operation process is shown. A valve generator 10 and a conductor pattern 11 for pressing the generated bubble against the tip 14 of the plateau are placed on the tip 14 of the grooved portion 3. In advance, a magnetic field in the same direction as the bias magnetic field 17 is applied to the entire effective chip to magnetize the entire chip.
Saturate in the direction of. And a suitable bias field Hz
When a pulse current is applied to this bubble generator 10 in the state of adding a bubble, a valve is generated in 14 and the bubble is prevented from expanding in the direction of 13 by the current magnetic field generated from the conductor pattern 11, and the Hz is lowered. When the bubble rises, the bubble moves 3 along the plateau boundary 4.
Try to stretch inside. Then, the striped domains extending along the groove 3 become U-shaped with the tips thereof entering the introduction guides 15 and 15 ', respectively. A pulse current is applied to the conductor pattern 12 with respect to such a stripe domain, and a portion extending into 15 and a portion extending into 15 ′ of the stripe domain in the region between the two conductor patterns are separated. To join. The shape of the bonded stripe domains is determined by the effects of the bias magnetic field Hz and the surface tension of the domain wall that minimizes the surface energy of the domain wall. When the bias field Hz is adjusted, the ring-shaped stripe domain finally becomes as shown in FIG. A VBL pair, which is an information carrier, is written in the outer domain wall 7 of the domain 6. The groove 13 is for a gate that connects a major line 16 that represents information regarding the presence or absence of a valve necessary for a Bloch line memory and a ring-shaped stripe domain portion that stores information regarding the presence or absence of a VBL pair.

The depth of the first groove 3 was actually evaluated in the range of 5% to 40% of the total film thickness of the stripe domain holding layer, but there was no problem in forming the ring stripe domain. FIG. 2 shows an example of a major / minor configuration in which a large number of the units shown in FIG. 1 are arranged.

(Embodiment 2) FIG. 3 shows a thin groove 19 dug along the peripheral edge 4 of the plateau 2 of FIG. When the inner domain wall of the ring-shaped domain bulges into this groove, the inner domain wall becomes more difficult to disengage from 4 as compared with the structure of FIG. 1, and the stability of the ring-shaped domain is further increased. A contour etching method (for example, Technical Report SSD-7
7-42). After forming a Mo or Cr thin film, a pattern mask to be contour-etched is formed with a resist, and is etched with CCl ₄ / O ₂ gas plasma.

(Effects of the Invention) According to the present invention, the instability in which the inner domain wall of the ring-shaped stripe domain is separated from the step of grooving step, which has been a conventional problem, has been greatly improved. Since the non-uniformity of the potential well in the domain wall portion of the stripe domain stabilization can be eliminated as usual, the transfer stability of the Bloch line pair is increased, and thus the reliability of the Bloch line memory is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a structural example of a ring-shaped stripe domain holding method of the present invention, and FIG. 2 is a diagram showing a configuration example of a chip using the try domain holding method of the present invention. FIG. 3 is a diagram showing an example of contour etching around the plateau. FIG. 4 is a diagram showing a structural example of a conventional ring domain holding method. In the figure, 1: stripe domain holding layer, 2: plateau, 3: first grooved part, 4: inner grooved boundary, 5: grooved outer boundary, 6: ring-shaped stripe domain, 7 : Stripe domain outer peripheral domain wall, 8: Magnetization direction inside the domain, 9: Magnetization direction outside the domain, 10, 11: Bubble generator conductor pattern, 12: Stripe domain coupling conductor pattern 13: Transfer gate part, 14: Groove moat Rib tip (bubble generating part), 15 and 15 ': Stripe domain tip introduction guide
16: major line (bubble transfer path), 17: direction of static bias magnetic field, 18: second grooved portion, 19: first groove by contour etching, third groove on inner boundary (around plateau) of grooved portion Horibe,
20: outer boundary of grooved portion, 21: valve generator, 22: conductor pattern for stripe domain coupling.

Claims (2)

[Claims] 1. A ring having an information reading means, an information writing means and an information accumulating means and formed on a ferromagnetic material (including ferrimagnetic material) film in which a direction perpendicular to a film surface is an easy magnetization direction. Using a pair of vertical Bloch lines composed of two adjacent vertical Bloch lines created in the Bloch domain wall at the boundary of the striped stripe domain as a memory information unit,
In a magnetic memory element having means for transferring the vertical Bloch line in a Bloch domain wall, a ring-shaped first grooved portion is provided on the surface of the ferromagnetic film, and the ring is formed on an outer peripheral portion of the ring-shaped groove. A second groove trench deeper than the first groove having a ring shape, and the ring-shaped stripe main is provided in the first groove groove having a ring shape in contact with an inner groove boundary. element. 2. A ring which has an information reading means, an information writing means and an information accumulating means and which is formed on a ferromagnetic material (including ferrimagnetic material) film in which a direction perpendicular to the film surface is an easy magnetization direction. Using a pair of vertical Bloch lines composed of two adjacent vertical Bloch lines created in the Bloch domain wall at the boundary of the striped stripe domain as a memory information unit,
In a magnetic memory element having means for transferring the vertical Bloch line in a Bloch domain wall, a ring-shaped first grooved portion is provided on the surface of the ferromagnetic film, and the ring is formed on an outer peripheral portion of the ring-shaped groove. A second groove trench deeper than the ring-shaped first groove, the ring-shaped stripe domain is provided in the ring-shaped first groove trench in contact with an inner groove boundary, and the ring-shaped first domain is provided. At the inner boundary of the groove, the third wall having the width of the domain wall
A magnetic memory element characterized by being provided with a grooved part.