JPH01302785A - Ceramic superconducting device - Google Patents

Abstract

PURPOSE:To operate a device with practical output voltage and high speed performance by arranging a laminated layer or U-shaped control line, making magnetic field generated by passing a current through the control line act on a ceramic superconductor. CONSTITUTION:On a superconducting magnetoresistive element 1, a U-shaped control line 5 is arranged, via an insulating film 10. When, in the state where the superconducting magnetoresistive element 1 is cooled at a temperature equal to or lower than a specified value, current is not made to flow through the control line 5, and magnetic field is not applied to the superconducting magnetoresistive element 1, it is in a superconducting state. When a current is made to flow through the control line 5, the generated magnetic field is converged on the superconducting magnetoresistive element 1, because the control line is U-shaped. As a result, the superconducting state of the superconductor 3 is broken, and resistance is exhibited.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention allows logical operations to be performed by controlling the characteristics of a ceramic superconductor using a magnetic field generated by a current flowing through a control line provided in close proximity. This relates to control lines for ceramic superconducting devices.

<Prior art> Josephson elements are known as logic circuit elements that use the characteristics of superconductivity. The Josephson elements used are elements between superconductors made of niobium, lead, or their alloys. 〇 <Problems that the invention will solve the solution of the invention, which is a structure that loses an extremely thin insulating film. It was difficult to do.

Furthermore, while Josephnon elements operate extremely quickly,
Since the output level was low, it was difficult to put this device into practical use due to noise and output circuit considerations.

The present invention is a superconductor device that solves the above-mentioned problems, is easy to manufacture, has high-speed operation characteristic of superconductors, and has a practical output level.
AND shown in 3-29526.

Although it is basically the same as an element that performs logical operations such as OR or XOR, it has been improved to operate with a small control line current input. To achieve this purpose, a single control line is used to apply a magnetic field to the ceramic superconductor, which is generated by passing a current through a conductor provided in close proximity to a ceramic superconductor having a pair of electrodes at both ends. Alternatively, it is also possible to have two or more, but the magnetic field is efficiently applied to the element by forming the magnetic field in the shape of a square. With the control line having the above configuration, a generated magnetic field of necessary strength can be applied to the ceramic superconducting element even with a small current. In addition, in the case of a ceramic-based superconductor with a thin thickness and a structure with weak junctions at grain boundaries, the superconducting state of the element can be broken even with a weak magnetic field applied, so it can be controlled with a small amount of current. According to the above, it is also possible to arrange multiple control lines and create a configuration in which independent currents flow through each one, and by changing the thickness and direction of the current flowing through each control line, various logical outputs can be generated. It is possible to configure a logic circuit element that outputs to a voltage electrode of a ceramic superconducting element.

〉 He discovered that a ceramic superconductor, whose grain boundaries are weakly bonded, breaks its superconducting state when exposed to a weak magnetic field and exhibits the electrical resistance of normal conduction.He invented a method for measuring magnetic fields using this phenomenon, and filed a patent application. No. 1982-233369 ``Superconducting magnetoresistive system'' has been filed.

The present invention utilizes the above-mentioned phenomenon of ceramic superconductors, and by arranging a laminated or U-shaped control line on top of the superconductor, the magnetic field generated by the current flowing through the control line can be effectively controlled. Since it often acts on ceramic superconductors, ceramic superconducting elements can be
Alternatively, the superconducting magnetoresistive element can be made to have electrical resistance.

To explain in more detail, a superconducting element having ceramic grain boundaries has a 10th
As shown in the figure, the electrical resistance RO exhibited by the element is completely zero, but when a certain critical magnetic field Hc is applied, the element suddenly exhibits electrical resistance, and as the applied magnetic field increases, the electrical resistance increases rapidly. The present applicant discovered a new phenomenon and filed the above-mentioned patent application, but the ratio of the change in resistance ΔR to the initial resistance RO of this element, ΔR/Ro, becomes infinite, and it is different from the conventional magnetoresistive element. It is a device that exhibits high performance that is incomparable to that of other devices.

That is, the direction of research into ceramic superconductors that has been progressing in many research institutes recently is to improve the critical temperature (Tc), critical magnetic field (He), and critical current (Jc). have conducted various studies on the ceramic superconductors mentioned above, and have found that some types of these superconductors (those with a weak bond between superconductor particles) are exposed to an extremely weak magnetic field (several Gauss) as shown in Figure 1O above. They discovered that the weakly coupled superconducting state is broken and exhibits electrical resistance, which increases rapidly with the strength of the applied magnetic field, and created a ceramic superconducting device that uses this low critical magnetic field phenomenon to operate as a new logic circuit element. It is.

The change in electrical resistance in response to the application of a magnetic field, as shown in Figure 10 above, is due to the fact that ceramic superconductors are composites composed of many superconducting crystalline particles, and there is an extremely thin insulator or resistor at the grain boundaries. In a superconducting state where there is a so-called weakly coupled superconducting state, such as when there is a point state of contact between particles, or where there is point contact between particles, and there is no magnetic field, there is a tunnel effect. etc., electrons move freely and the electrical resistance shows zero. In other words, a superconductor in a weakly bonded state of ceramic crystal grains, etc. As shown in the diagram 1-1iII, it can be equimetrically regarded as an aggregation of innumerable Josephson bonds +2+, +21°, . . .

When a magnetic field is applied to such a superconductor element, Josephson coupling 121°121,...
The superconductivity of the element is broken, that is, the superconductivity is broken from the weak coupling part by the application of a weak magnetic field, and the element begins to exhibit electrical resistance, and the electrical resistance increases rapidly as the strength of the magnetic field increases.

As is clear from the above principle, this property does not depend on the direction of the applied magnetic field, but is determined by the absolute value of the strength of the magnetic field, since the grain boundaries are randomly arranged. .

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing one embodiment of the present invention.

In FIG. 1, l indicates a pair of current electrodes 21.21 provided at both ends of the ceramic superconductor 30 and this electrode 21.21.
21 is a superconducting magnetoresistive element consisting of voltage electrodes 22 and 22 provided near 21, and 5 is a U-shaped control line 5 formed on this superconducting magnetoresistive element l via an insulating film 10. has been done.

Next, a method for manufacturing the device shown in FIG. 1 will be described in detail.

First, in order to fabricate the magnetoresistive element of the ceramic superconductor film used in this device, the substrate 7 is made of stabilized zirconia (YSZ) in the film forming process outlined in FIG. While keeping the temperature at 400℃, Y(
NO3)3 ・6H20゜Ba (NO3)2,
Cu (NO3)2 ・3H20 YIBFLzCu3
0t
It was sprayed to form a --like film with a thickness of 5 μm, and a ceramic film was formed by thermal decomposition and oxidation, followed by annealing in air at 950° C. for 60 minutes and at 500° C. for 10 hours. The resistance of the ceramic superconductor film prepared in this way is 10
It starts to fall from 0k and shows completely zero resistance at 83.

Next, in order to process this ceramic high-temperature superconductor film into @50μm and 30mm length to form superconductor 3, a resist was applied and processed into thin stripes using a normal photolithography process to form a superconducting magnet. The superconductor portion 3 of the resistance element 1 was manufactured. This ceramic high-temperature superconductor could be easily processed using a phosphoric acid-based etching solution.

An insulating film I made of polyimide resin is formed on this superconductor 3.
After forming the O, in order to fabricate the electrodes 21 and 22 and the control line 5 for generating a magnetic field, a wiring pattern is formed using the Ti vapor deposited film again by the photolithography process and the lift-off method of the Ti vapor deposited film. A ceramic superconducting device of the present invention shown in FIG. 1 was manufactured.

The ceramic superconducting magnetoresistive element 1 used in this example is as follows:
The insulating layers and point contacts intervening in the grain boundaries become weakly coupled, which is considered to be an aggregate of Josephson couplings, and the relationship between the applied magnetic field and the element resistance suddenly changes from zero resistance state to a certain magnetic field, as shown in the fJrJ2 diagram. A resistance appears, and the rate of change of that resistance is extremely large. In addition, the magnitude of the magnetic field (threshold value) at which resistance suddenly appears and the rate of increase in resistance can be controlled by the magnitude of the constant current flowing through this ceramic superconducting magnetic sensor l.A current of 10 mA is applied to a straight Ti conductor wire. When you run
The strength of the magnetic field at a distance of approximately 50 μm from the conductor wire is 0.
It will be about 4 Gauss. Looking at the characteristic graph of the superconducting magnetoresistive element in Figure 2, the strength of this magnetic field is 20μ when a constant current of 2 mA is passed through the ceramic superconducting magnetoresistive element.
It was found that an output of V can be obtained.

From the above experiments, in the first example, the width of the control line 5 is 30 μm, the thickness is 1 μm, the shape is as shown in FIG. The distance was set to 50 μm. The thickness of the insulating film 10 was about 1 μm. In the above configuration, at least when the superconducting magnetic sensor l is cooled to a temperature below 83, no current is passed through the conductor 5, and the superconducting magnetoresistive element When no magnetic field is applied to 1, by passing constant current ■ to terminals a+b,
The magnetic field created by the current breaks the superconducting state of the superconductor 3 and exhibits resistance, so as shown in Figure 3, 0.5 pico An output of 20 μV was obtained with a delay of about seconds. In addition, at this time, a superconducting magnetoresistive element! The constant current between terminals a and b is 2mA.
It was.

In the superconducting magnetic sensor equipped with a control line disclosed in the previous patent application No. 63-29526, the control line was made straight and the center distance from the element was 50 μm.

When a constant current of 2 mA is applied to the superconducting magnetoresistive element l to make its output voltage 20 μV, it is necessary to apply a current of IO mA to the straight parallel control lines, but the U-shaped laminated control of the present invention When it is a wire, the magnetic field generated by the current converges on the superconducting magnetoresistive element l, so the control wire 5 has a 5 mA
, an output voltage of 20 μV can be obtained from the element l by passing a current of 20 μV, which means that the input current can be reduced by half.

In the second embodiment shown in FIG. 4, a part of the magnetoresistive element l of the superconductor 3, which is provided with a pair of current electrodes 21 and a voltage electrode 22, is partially laminated via an insulating film lO. A control line 5 in the shape of a square and a control line 6 arranged parallel to the superconductor 3
This is a logic element constructed by using a film forming technique on a substrate 7.

Where the control lines 5 and 6 and the superconductor in FIG. 4 are parallel, the distance between their centers is 50 μm, and the line widths are 30 μm, 30 μm, and 50 μm. At this time, in order to obtain an output of 20 μV from the superconducting magnetoresistive element in which a constant current of 2 mA was applied as before, a current of 20 mA had to be applied to the control line 6.

In addition, currents 1 and I2 flowing through the control wires 5 and 6 are in the same direction, and the current flow is flowing through the control wire 5! The magnetic field acting on the superconductor 3 is H1, the magnetic field acting on the superconductor 3 due to the current I2 flowing through the control line 6 is H1, and the critical magnetic field of the superconducting magnetic sensor l when a predetermined constant current is flowing is Ho. As Hl <Ho, Hz<Ho, Hl +H2>Ho
- (Under the condition 11, only when current flows through control lines 5 and 6 at the same time, an output voltage is generated between terminals cod as shown in Figure @5, resulting in an AND logical output. For example, ■!
A current of 3 mA as Iz and 15 mA as Iz
．． 6, an output voltage of 20 μV or more was obtained between terminals END only during the period when currents I and I2 were flowing at the same time.

Also, Hl>Ha, Hl>HO, l Hl Hz
Under the condition of l < Ho - (2), if the directions of the currents I+ and I2 flowing through the control line 5 and control line 6 are reversed as shown in Fig. 6, the current between terminals c and d will change as shown in the seventh factor. current I
1. An output voltage was obtained between the terminals C9d only during the period when only one of I2 was present, and an exclusive OR logic output was obtained. Also, under this current condition, the current I
By flowing t and Iz in the same direction, an OR logic output will be obtained.

In the above embodiment, the values of the current values II and I2 are appropriately selected, but the present invention is not limited to this. For example, the current values flowing through the control lines 5 and 6 It and E2 are set to constant values, and the distance between the superconductor 3 and the control line 5 or 6 is appropriately selected, and the control lines 5 and 6 are placed at a position that satisfies the above equation (1) or (2). It is also possible to provide one.

In addition, when manufacturing the device of the present invention, the method is not limited to the above-described method, and the control line 5.6 or the superconducting magnetic sensor 1 may be formed using a thin film by sputtering, MOCVD, electron beam evaporation, etc. results can be obtained, and further miniaturization of the processed shape can be expected.

Further, although the ceramic high temperature superconductor film used in the examples of the present invention was YIBazCuzOt-x, other B1-8r-Ca-Cu-0 series or T I- It goes without saying that similar results can be obtained by using a high-temperature superelectric material having components such as Ca-B a -Cu-0.

Furthermore, the arrangement relationship between the superconductor 3 and the control lines 5 and 6 is not limited to the above embodiment, and as shown in FIG. The other control line 6 may be arranged parallel to the superconductor 3 as shown in the figure, or may be laminated on the control line 5.

As explained in the above embodiments, if the control line is laminated or shaped into a U-shape, the magnetic field due to the current close to the element will be converged inside the U-shape, and will be smaller than that of a straight control line. A magnetic field of the same strength can be applied to the ceramic superconductor using an electric current, making it possible to create an efficient control line.

By making the ceramic superconductor film with grain boundaries even thinner, the control magnetic field can be reduced and the output voltage can be increased.

Furthermore, if the control line is placed close to the superconductor via a thin insulating film, the magnetic field caused by the current in the control line can be effectively applied to the superconductor.

By combining the above improvements, it is possible to create a ceramic superconducting device that allows the magnetic field generated by the small control line current to effectively act on the superconductor, performs various logical operations at high speed, and has a practical output level. .

In addition, by thinning the film, miniaturizing the device, and reducing the current in the control line, magnetic noise to the surroundings is reduced, allowing for high-density integration.

<Effects of the Invention> As described above, according to the present invention, instead of using the G3-Sefson junction that artificially creates an extremely thin insulating layer as in the past, weak bonds that naturally exist in the grain boundaries of a ceramic superconductor are used. It performs logical operations using the superconducting magnetoresistive effect, making it possible to efficiently operate devices with practical output voltages and extremely high operating speeds unique to superconductors.

Further, as described in detail of the present invention, a portion of the control line is laminated to the superconductor via an insulating film or formed into a U-shape, so that the magnetic field due to the current of the control line is focused on the superconductor. It should be possible to operate with a small input current.

Furthermore, as explained in the examples, the control lines can be arranged in a plane, or they can be easily multilayered using an insulating film of resin such as polyimide or oxide such as SiO2. It can be made into a device that performs various logical operations.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of an embodiment of the ceramic superconducting device of the present invention, FIG. 2 is a diagram showing an example of the characteristics of a ceramic superconducting magnetoresistive element, and FIG. 3 is a superconducting magnet due to the current flowing through the control line. FIG. 4 is a diagram showing the output response of a two-resistance element, and shows the case where the control lines for generating the magnetic field in another embodiment of the ceramic superconducting device of the present invention are arranged in the same direction. A plan view showing the configuration, Figure 5 is the 4th
A diagram showing the relationship between the output response and the control line current when the current directions of the control lines are in the same direction according to the configuration shown in the figure. Figure 6 shows the relationship between the two control lines that generate a magnetic field in another embodiment of the present invention. Figure 7 is a diagram showing the configuration when the current directions are opposite to each other.
FIG. 8 is a plan view showing the configuration of still another embodiment of the ceramic superconducting device of the present invention; FIG.
FIG. 9 is a diagram showing a schematic configuration of the ceramic superconducting film manufacturing apparatus used for manufacturing the example device of the present invention, FIG. 10 is a diagram showing an example of the characteristics of a superconducting magnetoresistive element, and FIG. 11 is a diagram showing a superconducting magnetic resistance element. 21.21. Current electrode, 22.22. Voltage electrode, 3. Superconductor, 5°6... Control line, 7... Substrate, 10... Insulating film. Agent Patent attorney Takeshi Sugiyama (and 1 other person) Figure 9c; -yyu (8pgstt + aqua Figure 1O Figure 11)

Claims (1)

[Scope of Claims] 1. Comprised of a ceramic superconducting element having magnetoresistive characteristics and having at least one pair of electrodes, and a conductor provided in close proximity to the ceramic superconducting element, the above-mentioned A ceramic superconducting device characterized in that at least a part of a control line for controlling conductivity of a ceramic superconducting element has a laminated structure with a thin insulating film interposed therebetween. 2. The ceramic superconducting device according to claim 1, wherein the control wire has a U-shaped folded shape, and a magnetic field generated in the conductive wires on each side by a current acts on the ceramic superconducting element. 3. The ceramic superconducting device according to claim 1 or 2, wherein the ceramic superconducting element is provided with two or more control lines capable of individually controlling current. 4. The ceramic superconducting device according to claim 1, wherein the ceramic superconducting element is made of a film-like ceramic superconductor formed on a non-magnetic substrate.