JPS62293583A - Bloch line memory and its manufacture - Google Patents

Abstract

PURPOSE:To improve the position accuracy and transfer accuracy of paired Bloch lines by forming a heating resistor of a shape corresponding to a magnetic domain on the surface of a magnetic thin film and providing a power application means to the heating resistor. CONSTITUTION:A magnetic garnet thin film 4 is provided on a nonmagnetic garnet substrate 2. A film of HfB2 is formed on the entire face of the thin film 4 and patterning is applied to the film 20 so as to leave only a flat shape part slightly larger than the flat shape of an objective stripe magnetic domain 6. Then electrodes 22, 23 are formed by patterning on a prescribed location of the thin film 4 and the heat resistor 20. Then an upward bias magnetic field Hb is applied externally, a pulse voltage is applied between the electrodes 22 and 23 to give a pulse current to the resistor 20. Thus, a magnetic bubble 7 is generated on the thin film 4 corresponding to any of the maximum point of two temperatures and the stripe magnetic domain 6 corresponding to the heating resistor at the position formed in advance with the resistor 20 is formed accurately and stably.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a Bloch line memory. 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 external memory for computers, memory for electronic files, memory for still image files, etc., there are magnetic tapes, Winchester disks, floppy disks, optical disks, magneto-optical disks, magnetic bubble memories, etc. Various types of memory devices are used. Among these memory devices, other memory except 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 fixedly on the information track or reproduces the 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 the quality of recorded and reproduced signals may deteriorate due to insufficient control. The quality of recorded and reproduced signals deteriorates due to vibrations in the head moving mechanism and dust adhering to the surface of the memory, and in the case of memories such as magnetic tapes that perform recording and reproduction while in contact with the head, wear due to sliding occurs. 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 if this control is insufficient, the quality of the recording and reproduction signal may deteriorate. A problem has arisen.

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 there is no need for relative movement with the second card, the above-mentioned problems do not occur even when the recording density is increased, and it is thought that high reliability can be achieved.

However, magnetic bubble memory uses circular magnetic domains (
bubbles) are used as information bits, the minimum bubble (diameter o
, 3 pm), the limit of the Q density is several tens of Mpi)/crn', and it is difficult to further increase the density.

Therefore, recently, blown 2-hole line memory has been attracting attention as a memory having a recording density that exceeds the recording density limit of the above-mentioned magnetic bubble memory. This Bloch line memory uses, as information bits, a pair of Neel domain wall structures (Bloch lines) sandwiched between Bloch domain wall structures that exist around magnetic domains generated in a magnetic thin film, so it is different from the above-mentioned magnetic bubble memory. It is possible to increase the recording density by nearly two orders of magnitude. For example, when using a garnet film with a bubble diameter of 0.5 gm, it is possible to achieve a recording density of 1.6 Gbit/crn' [[Nikkei Electronics J, August 15, 1983, p. 141-167
reference].

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

In the figure, 2 is a substrate made of non-magnetic garnet such as GGG or NdGG, and a magnetic garnet thin film 4 is provided on the substrate. The film can be formed by, for example, liquid phase epitaxial 1171i or inverse injection (LPE method), and its thickness is, for example, about 5 μm. 6
is a striped magnetic domain formed in the magnetic Gurney 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, 5 IL steps, and the length is, for example, about 10 gm. Also, /j1
The thickness of the wall 8 is, for example, about 0.5 pm. 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 (that is, the side 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 illustrated, 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 "1" and "0". The Bloch line pairs exist at regular positions in the domain wall 8, that is, in any of the potential wells. Further, each Bloch line pair is sequentially transferred to an adjacent potential well by applying a pulsed magnetic field perpendicular to the substrate surface. Thus, the recording of information to the Bloch line memory (writing of Pro7 Hol line pairs to the domain wall 8) and the reproduction of the information recorded in the Bloch line memory (reading of the Bloch line pairs in the domain wall 8) are performed using the Bloch line memory. This can be carried out at predetermined positions while transferring the pairs within the domain wall 8. 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. As a means for applying a pulsed magnetic field for reproduction, conductive patterns for pulsed current application are formed on the surface of the magnetic thin film 4 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, the position of the domain wall 8, that is, the position of the striped magnetic domain 6 must be kept stable. It is necessary.

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 an 81 wall. On the surface of the striped magnetic domain 6, there is a layer 111 having a width about half of the width of the magnetic domain.
2 is formed.

The groove can be formed, for example, by ion milling, chemical etching, or the like. The direction of magnetization within the magnetic domain 6 is downward, and the direction of magnetization of the portion of the magnetic g film 4 outside the magnetic domain 6 is upward.

However, the Bloch line memory having one or more grooved striped magnetic domains has the following 151 problems.

That is, in order to increase the recording density, it is necessary to make the width of the magnetic domains 6 as thin as possible and arrange many magnetic domains per unit area, but the width of the groove 12 is about half the width of the magnetic domains. For this reason, fine machining is required in response to higher density, making it difficult to perform groove machining with sufficient accuracy.

Furthermore, as described above, regular potential wells are created to stabilize the positions of the Bloch line pairs within the domain wall 8, but if the grooves 12 exist, the potential wells are disturbed due to the influence of the grooves 12, and the Bloch lines are This adversely affects the positional accuracy and transfer accuracy of line pairs.

In addition, when manufacturing the Bloch line memory as described above, in order to form and fix the striped magnetic domains 6, first a large bias magnetic field HB is applied to uniformly magnetize the entire magnetic thin film 4, and then the bias magnetic field is Magnetic bubbles are generated in a portion of the thin film 4 corresponding to the grooves by gradually reducing the size, and the bubbles are grown to form striped magnetic domains 6, and the magnitude of the bias magnetic field must be controlled. It's inconvenient.

Therefore, an object of the present invention is to solve the problems of the conventional Bloch line memory as described above, form stable magnetic domains and domain walls easily and with good accuracy, and improve the positional accuracy and transfer accuracy of Bloch line pairs. shall be.

[Means for Solving the Problems] According to the present invention, in order to achieve the above-mentioned objects, information is recorded using pro-7 holes in domain walls formed around magnetic domains in a magnetic thin film. A Bloch line memory carried out is characterized in that a heating resistor having a shape corresponding to a magnetic domain is formed on the surface of a magnetic thin film, and a means for energizing the heating resistor is provided.
Bloch line memory is provided.

Furthermore, according to unreleased IgI, a suitable method for manufacturing such Bloch lines is a process in which information is recorded using Bloch lines within the domain walls formed around the magnetic domains in the magnetic thin film 11!2. In a method for manufacturing a point line memory, a heating resistor and a pole for conducting electricity to the heating resistor are formed on the surface of a magnetic thin film, and the heating resistor is energized while applying a bias magnetic field from the outside. Provided is a method for manufacturing a Bloch line memory, which is characterized by generating heat by forming a magnetic domain in a magnetic thin film corresponding to the heating resistor.

[Example] A specific example of the present invention will be described below with reference to one drawing.

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 FIG. 1, 2 is a non-magnetic garnet substrate, and 4 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 IN film. 8 is a domain wall around the striped magnetic domain 6. A heating resistor 20 and an electrode 22 are arranged on the surface of the magnetic thin film 4.
．． 23 is given.

The heating resistor 20 is made of, for example, HfB2 or the like, and has a thickness of, for example, about 0.03 m.

Further, the heating resistor 20 is formed at a position corresponding to the magnetic domain 6 and the domain wall 8, and has a planar shape slightly larger than the magnetic domain 6. For example, if a striped domain has a width of 5I
In the case of Lm and length 1100p, the heating resistor 20 has a radius of 7gm and a length of 1054m. The electrodes 22.23 are made of, for example, AI, Al-Cu, Al/Mo, etc., and have a thickness of, for example, about 1ILm. The electrodes are provided at both ends of the heating resistor 20, slightly overlapping each other. Note that a voltage applying means (not shown) is connected between these pair of electrodes.

The direction of magnetization within the striped magnetic domain 6 is downward, and the magnetization outside the magnetic domain 6 is downward. 1llll! The direction of magnetization in the portion 24 is upward. Further, HB is a bias magnetic field applied from the outside and directed upward.

Within the domain wall 8, a pair of Bloch lines (not shown) stably exist.

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

FIG. 2(a) is a partial plan view showing a state in the middle of the process in an example of the method for manufacturing the Bloch line memory of the above embodiment, and FIG. 2(b) is a sectional view taken along line BB.

First, a magnetic garnet thin film 4 is deposited on a non-magnetic garnet substrate 2 by liquid phase epitaxial growth. Then, HfBzv2 is applied to the entire surface of the thin film 4 by sputtering.
0 is formed into a film with a thickness of about o and an i-pot m, and the film is patterned using a photolithography technique so as to leave only a portion with a planar shape slightly larger than the planar shape of the intended striped magnetic domain 6.

Next, in the same manner, electrodes 22 and 23 are patterned into predetermined shapes at predetermined positions on the surfaces of the magnetic thin film 4 and heating resistor 20.

Next, while applying an upward bias magnetic field HB from the outside, a pulse voltage is applied between the electrodes 22 and 23 to cause a pulse current i to flow through the heating resistor 20. is 0.1p, mj width is 7JLm
In this case, it is appropriate to use a current value of 200 mA and a pulse intensity of about 1 s. 100ns from the rise of this pulse current application
The temperature distribution in the plane of the heating resistor after a certain period of time is shown in Figure 2
As shown in a), there are two maximum temperature points at symmetrical positions.

When the temperature at this maximum point exceeds a critical value, a magnetic bubble 7 is generated in a portion of the magnetic thin film 4 corresponding to either of the two maximum points, as shown in FIG. 2(b). The probability of a bubble occurring at a position corresponding to either local maximum point is the same. The temperature criticality described above is determined by the thickness of the magnetic garnet FM film 4, saturation magnetization, anisotropic magnetic field, etc., but in the case of a 5pLm bubble thin film for forming a stripe magnetic domain with a width of 5gm as in the above example, the temperature criticality 200, which is about the same as one temperature
It is around ℃. The characteristics of the pulse voltage yi,i are set so as to obtain a predetermined heat generation for generating such a bubble.6 The generated magnetic bubble 7 is FMlhi! below the heating resistor 20. Since the temperature of the thin film portion 4 is higher than the other thin film portions, the magnetic domain grows to occupy this high temperature portion, forming a striped magnetic domain 6 as shown in FIG.

When the L pulse current is cut off, the heating resistor 20 gradually cools down, and the striped magnetic domains 6 tend to contract accordingly. However, when the heating resistor 20 is formed, the magnetic %jj film portion corresponding to the resistor A strain is generated, and in the presence of an appropriate bias magnetic field HB, a potential based on the strain prevents contraction, and the shape and position can be kept stable.

According to the method described above, it is possible to accurately and stably form striped magnetic domains 6 having a shape corresponding to the heat generating resistor 20 at the position where the heat generating resistor 20 has been previously formed.

[Effects of the Invention] According to the present invention as described above, by simply causing the heating resistor to generate heat, stable magnetic domains can be generated at desired positions of the magnetic thin film while keeping the magnitude of the external bias magnetic field constant. In addition, since the dimensions of the heating resistor may be larger than the dimensions of the striped magnetic domains to be formed, even minute magnetic domains can be formed with good precision.
Il! 2. Since the film applied to the surface can be relatively thin, the surface can be kept almost flat, and a desired pattern can be well formed on the surface through the insulating layer. The positional relationship between the line pair writing means, reading means, transfer means, etc. and the domain wall can be kept stable, and good recording and reproduction can be performed.

[Brief explanation of drawings]

FIG. 1(a) is a partial top view of the Bloch line memory of the present invention, and FIG. 1(b) is a sectional view thereof taken along line BB. FIG. 2(a) is a partial plan view showing a state in the middle of the process in the Bloch line memory manufacturing method of the present invention;
Figure (b) is the BB sectional view. 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. 2: Substrate, 4: Magnetic thin film 1 6: Magnetic domain, 7: Magnetic bubble, 8: Domain wall, 10: Bloch line, 20: Heat generating resistor. 22, 23: Electrode. Agent Patent Attorney Minoru Yamashita Children Figure 2 (a) Figure 2 (b) ==9

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 heating resistor with a shape corresponding to the magnetic domain is formed on the surface of the magnetic thin film. A Bloch line memory comprising: a means for energizing the heating resistor; (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 heating resistor is provided on the surface of the magnetic thin film, and a heating resistor is attached to the heating resistor. A Bloch line memory is characterized in that an electrode for energization is formed, and a heating resistor is energized to generate heat while applying an external bias magnetic field to form a magnetic domain in a magnetic thin film corresponding to the heating resistor. manufacturing 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.