JPS61131290A - Detecting method of bloch line - Google Patents

Abstract

PURPOSE:To detect the Bloch line of a Bloch line memory with a high speed and with a low electric power consumption by changing a prescribed magnetic domain area having the Bloch line and detecting the corresponding magnetizing fluctuation. CONSTITUTION:To a conductor line 4 to insert at least one Bloch line 7 which exists at a magnetic wall 5 round a magnetic domain 3 formed at a magnetic garnet film 2 where a vertical magnetic field HB is impressed, the electric current flows mutually in the opposite direction and the direction of the electric current is changed. Then, the magnetic wall 5 is mutually oscillated and shifted to the outside and the inside, the magnetic domain area is changed and in correspondence, the magnetization is changed. The change of the magnetic domain area goes to be small and large in accordance with the existence of the Bloch line 7. Consequently, when the magnetization change in correspondence to the magnetic domain area change is detected with an optical method, etc., by using a magnet optical effect, etc., it is not necessary to transfer and detect the bubble by an external rotating magnetic field, electric current driving system, etc., the constitution is made simple and the Bloch line of the Bloch line memory can be detected at the high speed and with the low power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to solid state memories, particularly Bloch line memories.

(2) Prior art At present, external memory for computers, electronic file memory, still image file memory, etc., include various types of memory storage such as magnetic tapes, Winchester disks, floppy disks, optical disks, magneto-optical disks, and magnetic bubble memories. chairs are used. Among the above-mentioned memory processors, memories other than the magnetic bubble memory always involve relative movement between recording media such as tapes and disks and recording and reproducing heads. Therefore, for densification,
Problems such as tracking, running and abrasion between the medium and the head, problems with dust and vibrations, and problems with force pushing have occurred in optical disks and magneto-optical disks.

On the other hand, magnetic bubble memory does not require a mechanical drive;
It also has high reliability and was thought to be advantageous for increasing density. However, because magnetic bubble memory uses a circular magnetic domain (bubble) generated in a magnetic garnet film with an axis of easy magnetization perpendicular to the film surface as one bit, it is limited by the material characteristics of current garnet films. bubble(
Even if a diameter of 0.3 gm is used, the number per chip + M
B it is the limit of recording density, and unless materials such as hexaferrite and amorphous alloy can be used instead of garnet, it will be difficult to increase the density in magnetic bubble memories.

Recently, Bloch line memory has been attracting attention because it exceeds the recording sound intensity limit of the magnetic bubble memory. Bloch line memory is formed by Neel domain walls sandwiched between the Bloch domain wall structure, which is a transition region in which the direction of magnetization twist in the domain walls is opposite in the domain walls that exist around the magnetic domains that occur in the magnetic garnet film. It uses a region (Bloch line) as one bit, and can achieve nearly two-digit higher density than a magnetic bubble memory that uses a circular magnetic domain (bubble) as one pit. For example, if a garnet film with a bubble diameter of 0.51 Lm is used, a storage capacity of 1.6 GBit per chip can be achieved.

FIG. 1 shows a schematic diagram of a conventional Bloch line memory.
1 is a substrate made of group 60 garnet of GGG, NdGGl; 2 is a magnetic garnet film formed on the substrate 1 by LPE (liquid phase epitaxial growth); 3 is a striped magnetic domain; 4 is a magnetic garnet film 3 A bias magnetic field H3 is applied to the entire memory in the direction of the arrow in the figure. Information is stored on the domain wall of the striped magnetic domain 3 depending on the presence or absence of a pair of Bloch lines, and if there is a pair of Bloch lines, the information is stored at 1゛°.
, if there is none, it corresponds to "0P". The Bloch line pairs are regularly present at stable points provided in the striped magnetic domain 3, that is, at the potentia wells, and apply a pulsed magnetic field perpendicular to the substrate surface. The method for reading information from the Bloch line memory, that is, the method for detecting the presence or absence of a Bloch line pair, will be described below.

Figure 2 is an explanatory diagram of the conventional Bloch line detection method, in which the same numbers are given to the same parts as in Figure 1, 5 is a domain wall, 6 is an explanatory diagram.
indicates a separated bubble, and 7 indicates a Bloch line. Note that the arrow in the domain wall 5 indicates the direction of magnetization at the center of the domain wall, and the arrow in the conductor line 4 indicates the direction of current.

In FIG. 2(a), striped magnetic domains 3 are formed in the magnetic garnet film 2'', and Bloch lines 7 are present in the domain walls 5. However, the potential well is not illustrated here. Two conductor lines 4 are provided across the stripe magnetic domain 3, and when pulsed currents in opposite directions are passed as shown by the arrows in the figure, the magnetic field created by the current flowing through the conductor lines 4 is generated across the stripe magnetic domain 3. Since the magnetization direction is opposite to the magnetization direction, the magnetic domain sandwiched between the two conductor lines 4 is contracted, and the domain wall 5 moves as shown by the broken line in the figure. When the amount of current is further increased, as shown in FIG. 2(b), both domain walls merge and the tips of the striped magnetic domains 3 become bubbles 7 and separate. After the current is stopped, the remaining stripe magnetic domain 3
A Bloch line similar to that before separation appears at the tip, and the size of the magnetic domain also recovers.

FIG. 3(e) shows the case where no Bloch line exists. At this time, when a current is applied to the conductor line 4, two lines appear as in the case of FIGS. It is possible to move the domain wall at a position sandwiched between the conductor lines 4, and by further increasing the amount of current, the domain walls on both sides can be combined. However, in Figure 2 (a) and Figure 2 (C) where Bloch lines exist, the magnetization direction within both domain walls sandwiched between two conductor lines is (a).
In the case of (C), the directions are the same, and in the case of (C), the directions are opposite. Therefore, when the two domain walls are combined, the interaction (exchange interaction) that acts between the magnetizations of the domain walls is different, and the Bloch line 7 When , the current value for merging the domain walls is smaller than when it does not exist. Therefore, by selecting the current to be applied to the conductor line 4 between the current value required to merge the domain walls when the Bloch line 7 exists and the current value required when the Bloch line 7 does not exist, the Bloch line 7
The presence or absence of the Bloch line 7 can be made to correspond to the presence or absence of the separated bubble 6, and the presence or absence of the Bloch line 7 can be determined by detecting the bubble 6 in the same manner as the conventional magnetic bubble memory.

In the conventional Bloch line detection method described above, it is necessary to separate striped magnetic domains each time a Bloch line is detected, and in addition, the separated bubbles are separated using an external rotating magnetic field, a current drive method, etc. Since it has to be transferred and detected, the configuration is complicated and it was not possible to increase the speed of mouth detection.

Furthermore, it has the disadvantage of high power consumption.

(3) Summary of the Invention An object of the present invention is to eliminate the drawbacks of the prior art described in -I- and to provide a high speed, low power consumption Bloch line detection method.

The Bloch line detection method according to the present invention detects the Bloch line by means of changing the area of a predetermined magnetic domain having the Bloch line, and means for detecting magnetization fluctuation caused by the change in the predetermined magnetic domain area. It is characterized by

”-Means for changing a predetermined magnetic domain area include those using a local magnetic field and those using photothermal effects, and the magnetic domain area can be changed both statically and dynamically. In addition, the means for detecting the magnetization changes include those that utilize the magneto-optical effect of polarized light flux, such as the Faraday effect or the Kerr effect, or those that use an ordinary MR element, Hall element, etc. to detect magnetic flux changes using an electric (4
) Embodiment FIGS. 3, 4, and 5 are explanatory diagrams showing an example of the method for detecting Bloch lines according to the present invention. FIG. The figure shows an example of the configuration of an optical system for detecting protuberance lines, and FIG. 5 shows the output of a photodetector. Here, 1 to 7 refer to the same things as in FIGS. 1 and 2, 8 is a light spot, 9 is a light emitting part such as a semiconductor laser or a pin photodiode, and lO is a diverging luminous flux emitted from the light emitting part 9. A collimator lens for collimating the beam; l is a polarizing plate; 12 is a condensing lens for forming a light spot 8 at a predetermined position on the striped magnetic domain 3; 13 is an analyzer; 14 is a photodetector; 12' is a light beam. Detector 1
4, a condenser lens that collects the light transmitted through the analyzer 13, 15
16 shows the output of the photodetector 14 when the Bloch line 7 exists in the optical spot 8, and 16 shows the output of the photodetector 14 when the Bloch line 7 does not exist.

In Figure 3, (YSmLuCa)3 (FeGe)5
012 and (YSmL'uCd)3 (FeGa)501
A perpendicular bias magnetic field H3 is applied to the magnetic garnet film 2, such as No. 2, downward from above with respect to the plane of the paper, and striped magnetic domains 3 are formed in the magnetic garnet film 2. Bloch lines 7 are present in the domain wall 5 around the striped magnetic domain 3. Furthermore, two conductor lines 4 are provided on the magnetic garnet film 2'' with at least one Bloch line 7 sandwiched therebetween. The Bloch line 7 stably exists between the conductor lines 4 due to the potential well,
When a current is passed through the conductor line 4 in the direction of the arrow in the figure, if the direction of the magnetic field generated by the current is equal to the magnetization direction of the striped magnetic domain 3, the domain walls 5 in the area sandwiched between the two conductor lines 4 are on the outside of each other. Move to.

Further, when the direction of the current is opposite to the direction of the arrow in the figure, the domain walls 5 move inward from each other.

In FIG. 4, the diverging light beam emitted by the light emitting unit 9 becomes a parallel light beam by the collimator lens 10, is linearly polarized by the polarizing plate 11, and passes through the condensing lens 12 to form the light spot 8 shown in FIG. is irradiated to a predetermined magnetic domain position. The light flux transmitted through the magnetic garnet film 2 and the substrate 1 undergoes rotation of the plane of polarization due to the Faraday effect due to the magnetization within the striped magnetic domains 3, and the rotation angle of the plane of polarization is determined by the magnitude of the magnetization of the striped magnetic domains 3 within the optical spot 8. It is proportional to that.

After passing through the analyzer 13, the transmitted light beam enters the photodetector 14 via the condenser lens 12'. As described above, the output signal from the photodetector 14 depends on the magnitude of the magnetization of the striped magnetic domain 3, that is, the change in the area of the magnetic domain. The output produced by the device 14 also changes approximately sinusoidally.

Here, if a Bloch line exists in the domain wall between the two conductor lines 4, when the domain wall vibrates, the domain wall width becomes narrower than that of a domain wall without a Bloch line, so the braking force against domain wall movement becomes stronger. . In other words, since the magnetic inertia force is large, the area change of the striped magnetic domain 3 becomes small.

Therefore, the vibration value of the output obtained from the photodetector 14 is smaller than when the Bloch line does not exist, and as shown in FIG. occurs, which makes it possible to determine the presence or absence of Bloch lines.

Since the Bloch line can be directly detected by the method described above, the detection operation can be made faster, and the current flowing through the conductor line can also be reduced because there is no need to chop the striped magnetic domains.

FIG. 6 and FIG. 7 are diagrams showing an application example of the above embodiment, in which FIG. 6 shows a Bloch line memory having a plurality of striped magnetic domains, and FIG. 7 shows a configuration of a detection optical system of the Bloch line memory. An example is shown. The numbers in the figure indicate the same ones as in FIGS. 3 and 4. In addition, 17 is an A10 deflector,
It is an optical deflector such as an E10 deflector.

Here, the predetermined positions of the plurality of striped magnetic domains 3 are
The detection optical system shown in the figure is used to continuously irradiate the substrate 1 with a scanning light beam, thereby enabling high-speed reproduction in the Bloch line memory based on the same detection principle as in the previous embodiment.

In addition, the Bloch line within the domain wall 5 of the striped magnetic domain 3 is
By applying a vertical pulse magnetic field to the entire memory, data can be sequentially transferred within the domain wall 5. Further, an optical system in which a plurality of light emitting sections 9 and photodetectors 13 are arranged is also possible.

FIG. 8 shows another embodiment in which the predetermined magnetic domain area is changed, and the numbers in the figure refer to the same ones as in FIG. 3. In this embodiment, a predetermined magnetic domain area is changed using the photothermal effect. When the magnetic garnet film 2 is irradiated with a linearly polarized light beam in the same manner as in the above embodiment, the temperature of the irradiated part, that is, the light spot 8 becomes -R, and depends on the temperature characteristics of the material of the magnetic garnet film 2. The width of the striped magnetic domain 5 in the irradiation area changes. Therefore, by temporally changing the intensity of irradiated light from a light emitting unit such as a semiconductor laser, the area of the striped magnetic domain can be temporally varied. Using the wood method eliminates the need for conductor lines, which not only simplifies the configuration but also eliminates the need to consume power.

FIG. 9 shows a sectional view of another structure of the Bloch line memory, in which 18 is a light reflecting film, which is provided on the magnetic garnet film 2I-. The Bloch line memory having such a configuration can detect Bloch lines using the method of the above embodiment using the optical system shown in FIG.

In Figure i10, the light emitted from the light emitting part 9 is converted into a parallel beam by the collimator lens IO, linearly polarized by the polarizing plate 11, passed through the beam splitter 19, and then formed on the magnetic garnet film 2 by the condenser lens 12. A predetermined position of the striped magnetic domain 3 is irradiated. The incident light flux that has undergone modulation corresponding to the presence or absence of Bloch lines is reflected by the light reflecting film 1.
8, is modulated again, and returns to the original optical path. In other words, it undergoes two Faraday rotations. The reflected light, which has become a parallel beam of light through the condensing lens 12, has its optical path changed by the beam splitter 19 and passes through the analyzer 1.
3 and a condenser lens 12', and is captured by a photodetector 14. In the above configuration, the S/N ratio is improved by twice Faraday rotation of the plane of polarization.

FIG. 11 is a diagram showing another embodiment of the present Bloch line detection method, in which (A) is a top view of the Bloch line memory, (B) is a cross-sectional view, (C) is a side view, and 19 is a diagram showing a top view of the Bloch line memory. Electrode 20 for capacitance detection is a magnetostrictive material with magnetic garnet film 2
It is located at a predetermined position on the top. Note that the other numbers indicate the same items as in the above embodiment.

Due to the action of the magnetic field generated by passing a current through the conductor lines 4, the domain wall 5 between the two conductor lines 4 vibrates with different amplitudes depending on the presence or absence of Bloch lines as the current changes. Therefore, the area of the striped magnetic domain 3 sandwiched between the inner conductor lines 4 changes, and the distribution of the magnetic field changes as shown by the broken line arrow in FIG. 11(b). At this time, the magnetic field distribution applied to the magnetostrictive material 20 filled between the two capacitance detection electrodes 19 changes, and the ancient city changes as the effective distance between the two capacitance detection electrodes 19 changes. . By detecting the capacitance change, high-speed detection is possible to determine the presence or absence of a Bloch line, and an optical system like the above embodiment is unnecessary, resulting in a simple configuration.

(5) Effects of the originating Z (1) As explained above, the Bloch line detection method according to the present invention does not require conversion into bubbles, and enables high-speed detection 111 of Bloch line memories having large volumes. This is a detection method that can achieve low power consumption.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional Bloch line memory. FIG. 2 is a diagram showing a conventional Bloch line detection method. FIG. 3, FIG. 4, and FIG. 5 are explanatory diagrams of the Bloch line detection method according to the present invention. Figure 6. FIG. 7 is a diagram showing a Bloch line memory using the Bloch line detection method of the present invention. FIG. 8 is a diagram showing another method of changing the predetermined magnetic domain area. FIGS. 9 and 10 are diagrams showing another embodiment of the Bloch line memory using the Bloch line detection method of the present invention. FIG. 11 is a diagram showing another embodiment of the Bloch line detection method of the present invention. ■---Substrate, 2-1-1 magnetic garnet film, 3-1--stripe magnetic domain, 4-1-1 conductor line, 5-1-
-Domain wall, 6----magnetic bubble, 7----brochure line, 8-111 light spot, 9--11 light emitting part, 10
----Collimator lens, 11--m-polarizing plate, 12
, l 2'---One condensing lens, 13---One analyzer, 14---One photodetector, 15.16---Output of photodetector, 17---Light polarizer , 18-- one light reflective film, 19-
--One immersion detection electrode, 20---One magnetostrictive material. hmm

Claims (1)

[Claims] (1) In a Bloch line memory, a method for detecting a Bloch line is characterized in that a predetermined magnetic domain area is changed by vibrating a domain wall, and magnetization fluctuations caused by the change in the predetermined magnetic domain area are detected.