JP2713889B2 - Bloch line transfer method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Bloch line memory used as a magnetic storage element, and more particularly to a method of transferring a Bloch line which is a storage unit existing in a domain wall of a magnetic film in a Bloch line memory. About. <Prior Art> At present, various memory devices such as a magnetic tape, a winch-ester disk, a floppy disk, a magneto-optical disk, and a magnetic bubble memory are used for an external memory for a computer, an electronic file memory, a still image file memory, and the like. I have. Other memories except the magnetic bubble memory among the above memory devices always involve relative movement between a recording medium such as a tape and a disk and a recording and reproducing head. Therefore, with respect to high density, there are problems of tracking, running and abrasion between the medium and the head, problems of dust and vibration,
In addition, focusing and other problems have occurred with optical disks and magneto-optical disks. On the other hand, the magnetic bubble memory does not require a mechanical driving unit, has high reliability, and is considered to be advantageous for high density. However, since the magnetic bubble memory uses, as one bit, a circular magnetic domain (bubble) generated in a magnetic garnet film having an easy axis of magnetization perpendicular to the film surface, the minimum bubble (diameter) limited by the current material properties of the garnet film is used. 0.3μm) even if using several tens of Mbi per chip
t is also the limit of recording density, and there is not much difference in capacity even when comparing semiconductor memories that will be competitors in the future,
There was a problem that the range of application was very narrow. Recently, Bloch line memories have been attracting attention because the recording density of the magnetic valve memories has been exceeded. The Bloch line memory is a transition region in which the direction of the magnetization twist in the domain wall is reversed in the domain wall existing around the stripe-shaped magnetic domain generated in the magnetic garnet film,
That is, a storage unit is formed by using two regions (bloch line) formed by Neel domain walls sandwiched by the Bloch domain wall structure,
This pair of blot lines is used as one bit. Since the width of the Bloch line memory is generally about 1/10 of the magnetic domain width, the Bloch line memory can be increased in density nearly two orders of magnitude compared to the magnetic bubble memory in principle. For example, when a garnet film having a bubble diameter of 0.5 μm is used, a storage capacity of 1.6 GBit per chip can be achieved. In the Bloch line memory, it is necessary to form a stable position of a Bloch line pair, which is a storage unit, to stably store information, and to stably transfer data one bit at a time at high speed. 6 and 7 are views showing a conventional method of stabilizing and transferring a Bloch line pair. FIG. 6A shows a pattern formed for stabilizing a Bloch line pair, and FIG. 6B. FIG. 3 is a diagram showing a state of a potential in a magnetic film and stabilization of a Bloch line pair based on formation of a stabilized hattern. FIG. 7A is a schematic diagram illustrating a method of transferring a Bloch line pair, and FIG. 7B is a diagram illustrating a pulse shape of a vertical pulse magnetic field. Conventionally, in order to stabilize a Bloch line pair, a stripe pattern 3 extending in a direction orthogonal to the longitudinal direction of the stripe magnetic domain 1 is formed as shown in FIG. The position intersecting with the striped pattern 3 is a stable point of the Bloch line pair. The stripe pattern 3 is formed of a magnetic easy axis perpendicular to the film surface in the stripe magnetic domain 1, a ferromagnetic film having an easy axis of magnetization in the width direction of the stripe in the film surface, or uniform in the magnetic film. A pattern is formed by performing ion implantation to an appropriate depth. By giving the distribution 4 of the magnetic field Hx in the longitudinal direction of the stripe domain 1 as shown in FIG. 6B along the domain wall 2 of the stripe domain 1 by the above-described ferromagnetic film or ion implantation, a pair with Hx is formed. The periodic potential well for the pair of Bloch lines 6 is formed by the Zeeman energy of the magnetization 7 in the domain wall between the Bloch lines to be formed. In the above configuration, as shown in FIG. 7 (A), by applying a pulse magnetic field _Hp⊥ perpendicular to the magnetic garnet film in the direction of arrow 8, the magnetization constituting the Bloch line is rotated by the gyroscopic force. In the case shown in FIG. 7A, the magnetization line moves in the direction of arrow 9 due to the rotation of magnetization, and
The data is transferred by bits. Here, in the above method, the potential wells with respect to the pair of Bloch lines are symmetrical, and if a simple square wave shape is applied to the Bloch line transfer pulse magnetic field, the rising Bloch line line pair of the pulse moves in the direction of arrow 9. It returns to its original position when it rises, and stable transfer to one side cannot be expected. To the rise time t ₁ as the graph 10 shown in the order FIG. 7 (B), the fall time
By making t ₂ long enough, it was transmitted in one direction. However, in the above-described method, since the two blot lines are simultaneously moved, there is a problem that the blot lines vibrate due to a suction force and a repulsive force between the blot lines, so that stable transfer is difficult. Further, since the distance between the Bloch lines constituting the pair is very narrow, the depth of the potential well due to Zeeman energy becomes shallow, and there is a problem that it is difficult to stabilize the Bloch line pair 6. Further, when a normal valve material is used for the magnetic garnet film, the fall time t ₂
Must be set to 1 μsec or more, which causes a problem that the Bloch line transfer speed is significantly reduced. Further, in order to generate a pulse shape as shown in the figure, there is a problem that an electric circuit becomes more complicated and power consumption becomes larger as compared with the case of producing a square wave pulse. <Summary of the Invention> It is an object of the present invention to provide a method of transferring a Bloch line that is stable and highly reliable in view of the above-mentioned conventional disadvantages. In order to achieve the above object, a method of transferring a Bloch line according to the present invention is to transfer a Bloch line existing in a domain wall of a stripe domain formed in a magnetic film having an easy axis of magnetization in a direction perpendicular to a film surface to the stripe domain. A method of transferring by applying a vertical pulse magnetic field perpendicular to the film surface of the film, wherein when applying the vertical pulse magnetic field to the stripe domain, an in-plane pulse magnetic field in the longitudinal direction of the stripe domain is applied to the stripe domain. Having a step of applying
The time when the in-plane pulse magnetic field rises is set earlier than the time when the vertical pulse magnetic field rises. According to the present invention, the driving force due to the in-plane pulse magnetic field and the driving force generated when the vertical pulse magnetic field rises act on the pair of blot lines, so that the blot lines can be accurately transferred one by one. Further features of the present invention are described in the following examples. <Examples> FIGS. 1 (A) and (B) and FIGS. 2 (A) to (D)
FIG. 2 is an explanatory diagram of a Bloch line transfer method according to the present invention, wherein 2 indicates a domain wall including a Bloch line pair, and 5 indicates magnetization in a domain wall other than the Bloch line pair. Reference numeral 6 denotes a pair of Bloch lines, and 7 denotes magnetization in a domain wall between the pair of Bloch lines. 8, a pulse magnetic field perpendicular to the magnetic film for applying a gyro force to the Bloch line and transferring it; 13, 13 ', an in-plane magnetic field H〃 in the longitudinal direction of the stripe magnetic domain for applying a driving force to the Bloch line to transfer the Bloch line in one direction It is. 14, 14 'represent the driving force F _H 〃 due to the in-plane magnetic field _H受 け る which the left Bloch line 18 receives. 15, 15 'represent the gyroscopic force F _Hp⊥ from the vertical pulse magnetic field H _p⊥ received by the left blow line 18; 16, 16' represent the force _received by the right blow line from the in-plane magnetic field H〃; This represents the force that the right side Blochler 19 receives from the vertical pulse magnetic field _{Hp #} . In FIG. 2A, reference numeral 4 denotes an in-plane magnetic field along a domain wall serving as a potential well for the Bloch line pair 6.
It is the distribution of H _x. In FIG. 2 (B), reference numerals 18 and 19 denote two Bloch lines constituting the Bloch line pair 6.
Also, in FIGS. 2 (C) and 2 (D), 20, 20 'represent the waveform of the in-plane magnetic field H _# , and 21, 21' represent the waveform of the vertical pulse magnetic field _{Hp #.} Street, in-plane magnetic field (pulse)
Is set earlier than the rise of the vertical pulse magnetic field. Δt and Δt ′ represent the time during which both H〃 and _Hp⊥ are simultaneously applied. Reference numeral 23 denotes a pitch Δx _p of a periodic distribution of the in-plane magnetic field Hx. The operation will be described below step by step. First, in FIG. 1 (A), a force F _{Hp の of} arrows 15 and 17 is applied to the two Bloch lines 18 and 19 in the same direction by the vertical pulse magnetic field H _{p し よ う and tends} to move to the left. At this time, the in-plane magnetic field H〃 in the direction along the domain wall
Is applied, a force F _Hと す る for expanding the pair of blot lines as shown by arrows 14 and 16 is applied. As a result, the left Bloch line 18 has a force of | F _Hp⊥ | + | F _H 〃 | A force of magnitude is applied to the left, and the right Bloch line 19
| F _Hp⊥ | − | F _H 〃 | Where F
_The speed V _{BL at which the} Bloch line moves due to Hp⊥ must be considered for the motion of the domain wall. Becomes Here, a is the length of the domain wall to be considered. In this case, it is sufficient to consider only the width of the Bloch line (πΛ). Γ is the gyromagnetic constant, Λ is the Bloch line width parameter, and the above equation (1) is V _BL = { _γH p _} (2). Next, the speed V _'BL which Bloch lines is moved by the force F _H 〃 caused by in-plane magnetic field H〃 is expressed by the following equation. Therefore, in the case of FIG. 1 (A), the speed V _{BL18 of the} Bloch line 18 is calculated from the equations (2) and (3). Next, likewise velocity V _BL19 of Bloch lines 19 Becomes Here, lambda and delta ₀ substantially the same as a good think for the size, vertical pulse magnetic field H _P⊥ effect than plane magnetic field H
The effect of 〃 is πQ ^1/2 / (2α) times. By using a magnetic film as used in conventional bubble material, Q> 1, the in-plane magnetic field H〃 than α«1 the magnetic field of the same degree as compared to the vertical pulse magnetic field H _P⊥ size at least one order of magnitude Bloch lines of It can be seen that it affects the speed. That is, a very large driving force can be obtained by H〃. As described above, by using a magnetic film such as that usually used for a bubble material, it is possible to move only one of the blot line 6 of the pair of blot lines 6 with an in-plane magnetic field H _# that is one digit smaller than the vertical pulse magnetic field Hp #. Similarly, when applied in the direction opposite to the H〃 as shown in FIG. 1 (B), the force F _H 〃 acts in a direction in which the distance between the Bloch lines pairs 6 is narrowed, only the right Bloch lines 19 pairs left Direction. The magnetic field distribution as shown in FIG.
The transfer of the Blochholin-in pair on the domain wall given Hx will be described below. Figure 2 Bloch lines: 6 as shown in (B) is a plane field H〃 perpendicular pulse magnetic field H _P⊥ where you are stabilized
When applied with waveforms such as 20, 21, only the blot line 18 is moved to the left by the above-described effect, and is moved to the next stable place. Accordingly, as shown in FIG. 2 (C), the blot line moves and stabilizes at the position 18 '. Next, an in-plane magnetic field H _磁界 and a vertical pulse magnetic field _Hp⊥ are applied as shown at 20 ′ and 21 ′ in FIG.
Only the left is moved to 19 '. The reason why the timing of the fall of the waveform of the in-plane magnetic field H _# is earlier than the _fall of the vertical pulse magnetic field Hp # is that the waveform is restored to the Bloch line pair 6 caused by the _fall of the vertical pulse magnetic field _Hp #. When the force -F _Hp⊥ acts, the in-plane magnetic field H
This is to prevent the driving force F _H 〃 by 〃 from working. In other words, in order to transfer a pair of Bloch lines stably in one direction, the vertical pulse magnetic field H is obtained by utilizing the constraint force on the Bloch line by the peak Hxp of the magnetic field distribution Hx in FIG.
_It can be seen that it is sufficient not to transfer only with _p⊥ . Therefore, considering the transfer speed, the above (2) and (3)
From the formula Is found. Also, to transfer across the potential well of Hx Condition is required. Further, in the case of FIG. 2 (C) due to the in-plane magnetic field H〃, it is necessary to prevent the Bloch line 19 from moving rightward, so that Hxp> H〃 (8). Therefore, according to equations (6), (7), and (8), By applying the in-plane magnetic field H〃 and the vertical pulse magnetic field Hp⊥ that satisfy the above condition, the _{blot line} can be stably moved in one direction. Further, in order to transfer only one bit, the moving distance by the time Δt at which H〃 and _Hp⊥ overlap with each other should be less than the pitch ΔXp of Hx. The stable bit-by-bit transfer can be performed with Δt satisfying the condition. Although the above principle is based on the case where the domain wall does not move, almost the same idea can be applied even when the domain wall moves. Next, a specific embodiment will be described with reference to FIG. 24 in the figure
Is a chip of a magnetic film having a stripe magnetic domain having a domain wall including a Bloch line, 25 is a coil for applying a magnetic field in the longitudinal direction of the stripe magnetic domain, and 26 is a coil for applying a magnetic field perpendicular to the magnetic film. is there. 27 is a pulse driver for passing a pulse current to 25 coils, and 28 is a pulse driver for passing a pulse current to 26 coils. Reference numeral 29 denotes a trigger generator for controlling the timing of the pulse drivers 27 and 28. With the simple magnetic field application system described above, stable transfer of a Bloch line pair can be performed. In this apparatus, the pulse dry 27, 28 is driven by the trigger pulse generator 29 at a timing satisfying the above (10). The pulse drivers 27 and 28 apply pulse currents having waveforms such as H _# 20, 20 'and _{Hp #} 21, 21' in FIGS. 2 (C) and 2 (D) to the coils 25 and 26. Here, (YSmLuGa) ₃ (GeFe) ₅ O ₁₂ was used as the magnetic film, the magnetic parameters were 4πM = 195 (Gauss), the stiffness constant A was 2.63 × 10 ⁻⁷ (crg / cm), and the anisotropy constant was Ku = 8690 (erg / cm ³ ) α = 0.11 and γ = 1.83 × 10 ⁷ are used. In the above description, the amplitude of the potential well Hx is set to 1
0e, and the pitch ΔXp of the period of the potential well is set to 1
μm, the transferable range of the in-plane pulse magnetic field amplitude H _{ vertical pulse magnetic field amplitude Hp} is the fifth from the above condition (a).
It becomes like the shaded area 30 in the figure. In FIG. 5, the area 31 cannot be transferred, and other areas are transferred but biy by
This is an area where bits cannot be transferred. Here, the in-plane magnetic field H〃
= 0.90E, when the vertical pulse magnetic field _H p⊥ 20 0e, overlap Δt of the condition (10) plane magnetic field pulse and the vertical magnetic field pulse from the equation may be below 20 nsec, easily controlled by a trigger diethyl Nereta 29 It is a possible value. FIG. 4 shows a further embodiment. In the figure, 24 is a chip having a magnetic film as in the previous embodiment, 27 'is a pulse driver for applying an in-plane magnetic field H〃, and 33 is a conductor layer formed on the chip 24 for applying an in-plane magnetic field H〃. , 34 indicate the direction of the current i flowing through the conductor layer 33. This embodiment is the same as the embodiment described above, except that the
Instead of 25, a current i31 is applied to the conductor layer 33 formed on the chip to apply H〃. Here, the longitudinal direction of the stripe magnetic domain is the x direction in the figure. In the present embodiment, the conductor layer 33
Since the spacing between the magnetic film 24 and the magnetic film 24 is small, the current i required to generate H〃 satisfying the condition (9) can be reduced, and the Bloch transfer can be performed with low power consumption. <Effects of the Invention> As described above, according to the method of transferring a Bloch line according to the present invention, since the Bloch lines constituting the Bloch line pair are separately driven and individually driven, the stabilization by the potential well can be easily performed, and the vibration due to the repulsive force between the Bloch lines. There is no need to consider such factors, and stable transfer can be performed. Further, the transfer of the Bloch line in one direction can be performed with a normal square wave pulse magnetic field, so that the peripheral circuit can be simplified. Further, since the difference between the timings of the two pulse magnetic fields is used instead of the width of the pulse magnetic field to move the pair of blot lines to the adjacent bit position, the control can be easily performed. In addition, it is not necessary to lengthen the _fall time due to the unidirectional transfer, and if the magnetic field H _平行 parallel to the magnetic film is made larger than the magnetic field ( _Hp⊥ ) perpendicular to the magnetic film, the transfer is performed with a smaller current value. And power consumption is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (A) and 1 (B) and FIGS. 2 (A) to 2 (D) are illustrations of a method of transferring a Bloch line according to the present invention. FIG. 3 is a schematic diagram of a magnetic field application device showing a specific embodiment of the present invention. FIG. 4 is a diagram showing an example of a magnetic field applying method showing a further specific embodiment of the present invention. FIG. 5 is a graph showing a range of an in-plane pulse magnetic field amplitude and a vertical pulse magnetic field amplitude which can be transferred by a Bloch line. 6 (A) and 6 (B) and FIGS. 7 (A) and 7 (B) are diagrams showing an example of a conventional method for transferring a pair of Bloch lines. 2 ... domain wall 5,7 ... direction of magnetization in domain wall 6 ... pair of Bloch lines 8 ... vertical pulse magnetic field 13 ... in-plane pulse magnetic field 18, 19 ... Bloch line

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Hiroshi Yoneda               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Akira Niimi               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Tetsuya Kaneko               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Nobuo Watanabe               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc.

Claims (1)

(57) [Claims] A Bloch line existing in a domain wall of a stripe magnetic domain formed in a magnetic film having an easy axis of magnetization in a direction perpendicular to the film surface is transferred to the stripe magnetic domain by applying a vertical pulse magnetic field perpendicular to the film surface of the magnetic film. Applying a vertical pulse magnetic field to the stripe magnetic domain, comprising applying a longitudinal in-plane pulse magnetic field of the stripe magnetic domain to the stripe magnetic domain, and setting a time at which the in-plane pulse magnetic field rises. A method for transferring a Bloch line, wherein the time is set earlier than the time when the vertical pulse magnetic field rises.