JPS6320796A - Bloch line memory and its production - Google Patents

Abstract

PURPOSE:To produce a stable magnetic domain and a stable magnetic wall in a simple and highly accurate way by forming a high melting point material part within the magnetic domain of a Bloch line memory. CONSTITUTION:A high melting point material part 20 is formed through a magnetic thin film 4 in a stripe magnetic domain 6 enclosed by a magnetic wall 8 provided to the film 4. Thus the position of the domain 6 is stabilized and the wall 8 is not easily moved by the variance of an external factor. In such a constitution, no groove part nor an ion implanting process, etc., are needed in the domain 6. Thus it is possible to obtain a stable magnetic domain and a stable magnetic wall in a simple and highly accurate way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to Bloch line memories. Bloch line memory can be applied to various electronic devices as a memory that can record information at extremely high density.

[Prior Art] At present, as memories such as external memory for computers, memory for electronic files, memory for still image files, etc., there are magnetic tapes, Winchester disks, flow 2P disks, optical disks, optical H1 disks, and magnetic bubbles. Various memory devices such as memory are used. Among these memory devices, other than the magnetic bubble memory, it is necessary to move the recording/reproducing head relative to the memory when recording or reproducing information. That is, with such relative movement of the head, the head records an information string definitively on the information track or reproduces an information string fixedly recorded on the information track.

However, in recent years, as there has been a demand for increasingly higher recording densities, tracking control to make the head accurately follow the information track has become more complex, and as a result of insufficient control, the quality of recorded and reproduced signals has deteriorated. The quality of the recording/reproduction signal may deteriorate due to vibrations in the head moving mechanism or dust adhering to the surface of the memory.Furthermore, in the case of memories such as magnetic tape that perform recording and reproduction while in contact with the head, sliding In the case of a memory that performs recording and reproduction without contact with the head, such as an optical disk, focusing control is required for focusing, and because this control is insufficient, the quality of the recording and reproduction signal deteriorates. The problem has arisen that

On the other hand, magnetic bubble memory can record information at a predetermined position and transfer the recorded information, and can reproduce information at a predetermined position while transferring the information. Since no relative movement is required, it is believed that the above-mentioned problems will not occur even when the recording density is increased, and high reliability can be achieved.

However, magnetic bubble memory uses, as information bits, circular magnetic domains (bubbles) generated by applying a magnetic field to a magnetic 8E film, such as a magnetic garnet film, whose axis of easy magnetization is perpendicular to the film surface. From the material properties of the garnet film, v1 is limited to the minimum bubble (diameter 0.
34m) even if you use fi+M beep) / crn'
is the limit of recording density, and it is difficult to further increase the density.

Therefore, recently, Bloch line memory has been attracting attention as a memory having a recording density that exceeds the recording density limit of magnetic bubble memory. This Bloch line memory is
Since it uses a pair of Neel Ia wall structures (Pro7 Hole line) sandwiched between Bloch domain wall structures existing around magnetic domains generated in a magnetic thin film as information bits, it is nearly two orders of magnitude larger than the magnetic bubble memory mentioned above. It is possible to increase the recording density. For example, when using a garnet film with a bubble diameter of 0.5 lumen, it is possible to achieve a recording density of 1.6 Gbit/crn' [[Nikkei Electronics 4, August 15, 1983, P141-167]
reference].

FIG. 3 shows a schematic side view of an example of the magnetic structure constituting the Bloch line memory.

In the figure, 2 is a substrate made of non-magnetic garnet such as cac or Naaal, and a magnetic garnet Q film 4 is provided on the substrate. The film can be formed by, for example, a liquid phase epitaxial growth method (LPE method), and its thickness is, for example, about 5 g.m. 6 is a striped magnetic domain formed in the magnetic garnet thin film 4, and a domain wall 8 is formed as an inner and outer boundary region of the magnetic domain.

The width of the striped magnetic domain 6 is, for example, about 5ILm, and the length is, for example, about loogm. In addition, domain wall 8
The thickness is, for example, about 0.5 m. As shown by the arrows, the direction of magnetization is upward within the magnetic domain 6, while the direction of magnetization is downward outside the magnetic domain 6.

The direction of magnetization within the domain wall 8 gradually rotates from the inner surface (part of the surface facing the magnetic domain 6) to the outer surface in a twisted manner.

The direction of this rotation is opposite on both sides of the Bloch line 10 that is perpendicular to the domain wall 6 as a boundary. Third
In the figure, the direction of magnetization at the central portion of the domain wall 8 in the thickness direction is indicated by an arrow, and the direction of magnetization at the Bloch line 10 is similarly indicated.

Note that a downward bias magnetic field HB is applied to the above-described magnetic structure from the outside.

As shown in the figure, there are two types of Bloch lines 10 with different magnetization directions, and the presence or absence of a pair of these Bloch lines corresponds to information "l" and "O". The Bloch line pair exists at regular positions in the domain wall 8, that is, at any one of the potential wells. Also,
Each Bloch line pair is sequentially transferred to an adjacent potential well by applying a pulsed magnetic field perpendicular to the substrate surface. Thus, recording of information to the Bloch line memory (writing of Bloch line pairs to the fii wall 8) and reproduction of information recorded in the Bloch line memory (reading of Bloch line pairs in the domain wall 8) are performed using the Bloch line memory. This can be done while transferring the pairs within the Fji wall 8, each at a predetermined position. The above information can be recorded and reproduced by applying a pulsed magnetic field of a predetermined strength perpendicular to the substrate surface to a predetermined portion.Although not shown in FIG. Magnetic thin film as a means of applying a pulsed magnetic field for reproduction! Conductive patterns for pulse energization are formed on the surface of 5i4 at predetermined positional relationships with respect to the striped magnetic domains 6, respectively.

[Problem to be Solved by the Invention 1] In the Bloch line memory as described above, in order to perform writing, reading and transfer of Bloch line pairs well, it is necessary to stabilize the position of the 51 walls 8, that is, the position of the stripe magnetic domains 6. It is necessary to maintain it.

Therefore, grooves have been conventionally provided on the surface of striped magnetic domains.

FIG. 4(a) is a plan view showing such a striped magnetic domain as described above, and FIG. 4(b) is a sectional view taken along line BB.

In the figure, 2 is a nonmagnetic garnet substrate, 4 is a magnetic garnet thin film, 6 is a striped magnetic domain formed in the thin film, and 8 is a domain wall. A groove 12 having a radius about half the width of the magnetic domain is formed on the surface of the striped magnetic domain 6.

The direction of magnetization within the magnetic domain 6 is upward, and the direction of magnetization of the portion of the magnetic thin film 4 outside the magnetic domain 6 is downward.

FIG. 5 is a diagram showing how the magnetic field changes due to the formation of the grooves 12 as described above in the magnetic rlvJ4.

That is, when a groove 12 with a depth d is formed in the magnetic thin film 4 with a thickness h as shown in FIG. A graph is shown in FIG. 5(b). As can be seen from the graph in Figure 5(b), the larger the groove depth d, the larger the magnetic field variation (which leads to stabilization of the 8i wall position), which further affects the position and transfer of the Bloch line pair. X that has a bad influence
The directional magnetic field becomes maximum when the depth d of the groove 12 is half the thickness h of the magnetic thin film s4, and becomes minimum, ie, 0, when d is 0 or h. Therefore, in the Bloch line memory, it is preferable for the depth d of the groove 12 to be equal to the thickness h of the magnetic thin film 4 in order to stabilize the position of the magnetic domain and to stabilize the position and transfer of the Bloch line.

However, the Bloch line memory having grooved striped magnetic domains as described above has the following problems.

That is, as described above, regular potential wells are created in order to stabilize the position of the pro7 hole pair within the domain wall 8, and the formation of this potential well is achieved by, for example, forming the magnetic domains 6 on the surface of the magnetic thin film 4. A pattern is formed by applying a large number of transverse line-shaped conductor layers or monolithic layers at a predetermined pitch in parallel, and grooves 12 are present on the surface of the magnetic thin film 4 at the positions of the magnetic domains 6. Therefore, it is difficult to form a good pattern, and therefore, it is difficult to improve the positional accuracy of the potential well.

Furthermore, when a conductor pattern for conducting current is provided on the surface of the magnetic thin film 4 so as to cross the striped magnetic domain 6 in order to apply a pulsed magnetic field for Bloch line pair transfer, the conductor pattern is not formed well (extremely In some cases, the wire may be disconnected), which may impede the Bloch line pair transfer.

In addition, the formation of grooves in striped magnetic domains as described above is
For example, this is done by dry etching using ion milling or by wafer etching, which involves destroying the crystal lattice with ion implantation and then treating it with phosphoric acid. Depending on these groove forming methods, it is possible to form grooves of such depth that they penetrate through the magnetic thin film with good accuracy. difficult to form. That is, in dry etching, it is necessary to perform ion milling for a long time in order to form the depth 111t12 that penetrates the magnetic thin film 4, and as a result, the temperature of the mask increases due to ion irradiation and the pattern is deformed. In addition, the width of the pattern at the top of the groove increases, making it impossible to expect a uniform effect on the domain walls. In addition, wet etching
Since it is possible to etch only about 100° in one process, it is necessary to repeat the ion implantation and acid treatment several times, which increases the processing time and reduces pattern accuracy.

SUMMARY OF THE INVENTION Therefore, the present invention solves the above-mentioned problems of the conventional blown two-horizontal memory, forms stable magnetic domains and domain walls easily and with good accuracy, and improves the positional accuracy and transfer accuracy of protube line pairs. With the goal.

[Means for Solving the Problems] According to the present invention, in order to achieve the above objectives, information is recorded using brochure lines within domain walls formed around magnetic domains in a magnetic thin film. A Bloch line memory is provided in which a high melting point material portion that can penetrate a magnetic thin film is formed within the magnetic domain.

Further, according to the present invention, as a method suitable for manufacturing such a Bloch line, a Bloch line memory is used in which information is recorded using blow 2 hole lines in a domain wall formed around a magnetic domain in a magnetic thin film. In the manufacturing method, a high melting point part is formed on a part of the substrate, a magnetic thin film is formed on the upper part of the substrate where the high melting point part is not formed, and the high melting point part is surrounded by applying a bias magnetic field. A method of manufacturing a Bloch line memory is provided, which is characterized by forming magnetic domains in a similar manner.

[Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1(a) is a partial plan view of a Bloch line memory according to the present invention, and FIG. 1(b) is a sectional view thereof taken along line B--B.

In Figure 1, 2 is a non-magnetic garnet substrate;
is a magnetic garnet thin film. Magnetic domains 6 having a striped planar shape are formed in the magnetic garnet thin film. 8 is a domain wall around the striped magnetic domain 6.

At the center of the striped magnetic domain 6, a high melting point material portion 20 having a convergence approximately half the width of the magnetic domain is formed. The high melting point material may be any material that has a melting point that does not interfere with the manufacturing process and use of the memory device, such as high melting point metals such as MO, Ta, and W, MgO, and A1203.
．． It is made of high melting point oxide such as 5i02. When the substrate 2 is non-magnetic garnet, oxides are more preferable in terms of compatibility with the substrate.

The direction of magnetization of the magnetic thin film within the striped magnetic domain 6 is upward, and the direction of magnetization in the portion of the magnetic thin film 4 outside the magnetic domain is downward. Further, HB is a bias magnetic field applied from the outside and is directed downward. Within the domain wall 8, a pair of Pro7 holines (not shown) stably exist.

In the Bloch line memory of this embodiment, there is a high melting point material portion 20 in the striped magnetic domain 6 which has the same effect as the groove in the conventional example, and the high melting point material portion penetrates through the magnetic thin @4. Therefore, the position of the striped magnetic domain 6 is stable, and even if some external factors change, the magnetic wall 8
does not move easily, allowing stable Bloch line writing, reading, and transfer.

The Bloch line memory of this embodiment as described above can be manufactured, for example, in the following manner.

FIGS. 2(a) to 2(d) are process diagrams showing an example of a method for manufacturing the Bloch line memory of the above embodiment. These figures show the same parts as in FIG. 1(b) above.

First, a high melting point material portion 2o is formed to a predetermined thickness on the entire surface of the nonmagnetic garnet substrate 2 by sparging. For example, thickness 2. Form a Mo film of m [Fig. 2 (
a)].

Next, milling is performed using an ion milling device,
The high melting point material portion 2o is patterned to correspond to the arrangement pattern of the patented Ripe magnetic domains 6. For example, acceleration voltage 500v, ion current 1 mA/crn
' Perform ion milling for 50 minutes [Figure 2 (b)]
.

Next, a magnetic thin film 4 is formed on the substrate z to have the same thickness as the high melting point material portion 20 . As this magnetic thin film, for example, a magnetic garnate thin film of (YSm) 3 (FeGa) s 012 can be used, and the film can be formed by a liquid phase epitaxial growth method. Conditions for this liquid phase epitaxial growth method include, for example, a growth temperature of 87°C.
Examples include a temperature of 5° C., a substrate rotation speed of 1100 rp during growth, a substrate pulling speed of 5 mm/min during growth, and a growth time of 4 minutes. According to the liquid phase epitaxial growth method, magnetic thin Wi 4 grows on the surface of the substrate 2 with uniform lattice constants, but does not grow on the high melting point material part 20. Therefore, by controlling the growth time, A magnetic thin film 4 can be formed on the surface of the magnetic material, that is, on a portion other than the high melting point material portion 20, to a thickness that is the same as that of the high melting point material portion [FIG. 2(c)].
.

Next, by applying a strong upward bias magnetic field of 200 millimeters or more from the outside to uniformly magnetize the magnetic thin film 4 upward, and further applying a downward bias magnetic field HB from the outside, the above-mentioned high melting point material portion is 20, domain wall movement is performed so as to surround the high melting point material portion and form a striped magnetic domain 6. The size of the magnetic domain 6 formed can be controlled by the size of the applied bias magnetic field [FIG. 2(d)].

According to the method described above, the striped magnetic domains 6 can be accurately and stably formed at positions corresponding to the high melting point material portions 20 formed in a pattern in advance.

[Effects of the Invention] According to the present invention as described above, stable magnetic domains and domain walls can be formed easily and accurately at desired positions of a magnetic thin film, and since the surface is flat, it is possible to form a stable magnetic domain and a domain wall in desired positions of a magnetic thin film. A desired pattern can be formed, and the position and relationship between the writing means, reading means, transfer means, etc. of the Bloch line pair thus formed and the domain wall can be kept stable, and good recording and reproduction can be performed. can.

[Brief explanation of the drawing]

FIG. 1(a) is a partial plan view of the Bloch line memory of the present invention, and FIG. 1(b) is a sectional view thereof taken along line B--B. FIGS. 2(a) to 2(d) are manufacturing process diagrams of the Bloch line memory of the present invention. FIG. 3 is a schematic perspective view of the magnetic structure constituting the Bloch line memory. FIG. 4(a) is a partial plan view showing the magnetic domains of a conventional Bloch line memory, and FIG. 4(b) is a sectional view taken along line B--B. Figures 5(a) and (b) show magnetic fl! ! FIG. 2 is a diagram showing how the magnetic field changes due to the formation of grooves in FIG. 2: Substrate, 4: Magnetic pJPA, 6: Magnetic domain, 8: Domain wall. lO: Bloch line. 20: High melting point material part. Agent Patent Attorney Jo Yamashita Figure 2 □ Dimensions

Claims (4)

[Claims] (1) In a Bloch line memory that records information using Bloch lines within a domain wall formed around a magnetic domain in a magnetic thin film, a high melting point material portion that can penetrate the magnetic thin film is formed within the magnetic domain. Bloch line memory featuring. (2) The Bloch line memory according to claim 1, wherein the magnetic thin film is a magnetic garnet thin film. (3) In a method for manufacturing a Bloch line memory in which information is recorded using Bloch lines in a domain wall formed around a magnetic domain in a magnetic thin film, a high melting point side is formed on a part of the substrate, Manufacture of a brochure line memory, characterized in that a magnetic thin film is formed on the upper part of the substrate where the high melting point part is not formed, and a bias magnetic field is applied to form a magnetic domain so as to surround the high melting point part. Method. (4) The method for manufacturing a Bloch line memory according to claim 3, wherein the magnetic thin film is a magnetic garnet thin film, and the formation thereof is carried out by a liquid phase epitaxial growth method.