JPH0810772B2 - Ceramic superconducting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention controls the characteristics of a ceramic superconductor by a magnetic field generated by a current flowing through a control line provided in the vicinity thereof to perform a logical operation or the like. The present invention relates to a control line of a ceramic superconducting device.

<Prior Art> A Josephson device is known as a logic circuit device using superconducting characteristics. The Josephson element used is
It has a structure in which an extremely thin insulating film is sandwiched between superconductors made of niobium, lead, or an alloy thereof.

<Problems to be solved by the invention> The above Josephson device requires an extremely thin insulating film of several tens of liters to obtain the Josephson effect. Therefore, it was difficult to manufacture an element having uniform characteristics.

Also, while the Josephson device operates extremely fast, its output level is low, so it was a device that is difficult to put into practical use due to noise and output circuits.

The present invention is a superconducting device which is easy to manufacture to solve the above-mentioned problems, and which has a high-speed characteristic peculiar to a superconductor and has a practical output level.
It is basically the same as the element for performing a logical operation such as AND, OR or XOR shown in −29526, but it is modified to operate with the current input of a small control line.

<Means for Solving the Problems> In order to achieve the object of the present invention, a magnetic field generated by passing an electric current through a conductor provided in the vicinity of a ceramic superconducting element having a pair of electrodes at both ends is applied. The number of control lines acting on the ceramic superconductor may be one, or two or more, but at least a part of the control lines is laminated with the ceramic superconducting element through an insulating film, and , U shape, and efficiently apply the generated magnetic field to the element. With the control line having the above-mentioned configuration, it is possible to apply a generated magnetic field having a required strength to the ceramic superconducting element with a small current. Also,
With a ceramic superconductor having a thin thickness and a structure in which the crystal grain boundaries are weakly joined, the superconducting state of the element is broken even with an applied magnetic field of a weak magnetic field, so that control can be performed with a small current.

Further, according to the present invention, it is also possible to arrange a plurality of the above-mentioned control lines and to make an independent current flow through each of them, and by changing the magnitude and direction of the current flowing through each control line, various A logic circuit element that outputs a logic output to the voltage electrode of the ceramic superconducting element can be configured.

<Operation> A ceramic superconductor with a weak crystal flow field is
We have found that the superconducting state is broken by a weak magnetic field and have the electric resistance of normal conduction, and we have applied for an invention of magnetic field measurement using this phenomenon, Japanese Patent Application No. 62-233369 "Superconducting Magnetoresistive System".

The present invention utilizes the above-mentioned phenomenon of a ceramic superconductor, in which a control line formed by stacking or U-shape is arranged on the superconductor, and a magnetic field generated by a current flowing through the control line is efficiently generated. Since it works well on the ceramic superconductor, the ceramic superconducting element or the superconducting magnetoresistive element can be brought into a state having electric resistance by a small amount of current of the control line.

More specifically, the superconducting element having a ceramic-based grain boundary has a tenth characteristic when a magnetic field is not applied.
As shown in the figure, the electric resistance R ₀ of the element shows a value of completely zero, but when a certain critical magnetic field Hc is applied, the element suddenly shows an electric resistance, and the electric resistance rapidly increases as the applied magnetic field increases. The present applicant has found a new phenomenon to do so and filed the above-mentioned patent application. However, the ratio of the resistance change ΔR to the initial resistance R ₀ of this element, ΔR / R _0, becomes infinite, and It is an element showing high performance that is incomparable to the magnetoresistive element.

In other words, the direction of research on ceramic superconductors, which is being advanced by many research institutions in recent years, is to improve the critical temperature (Tc), critical magnetic field (Hc), and critical current (Jc). As a result of various researches on the above ceramic superconductor, a certain kind of this superconductor (having a weak coupling state between particles of the superconductor) has an extremely weak magnetic field (several gausses) as shown in FIG. We found that the weakly-coupled superconducting state breaks, exhibits electrical resistance, and increases sharply with the strength of the applied magnetic field, and created a ceramic superconducting device that operates as a new logic circuit element using this low critical magnetic field phenomenon. Is.

As shown in FIG. 10 above, the change characteristic of the electric resistance with respect to the application of the magnetic field is that the ceramic-based superconductor is a combination body composed of many superconducting crystal fine particles, and an extremely thin insulator or resistor is formed at the grain boundary. Exists, or the contact between particles is in a point state, particles are in point contact with each other, so-called weak coupling state of superconductivity, tunneling effect in the superconducting state without magnetic field etc. As a result, electrons move freely and the electric resistance is zero. That is, a superconductor in a weakly coupled state of crystal particles such as ceramics can be regarded as an equivalently innumerable assembly of Josephson couplings 121, 121, ... As shown in FIG.

When a magnetic field is applied to an element of such a superconductor, the superconductivity of the Josephson couplings 121, 121, ... Is broken due to the influence of the magnetic field, that is, the application of a weak magnetic field breaks the superconducting state from the weak coupling portion, and the element is electrically connected. It becomes resistive and the electrical resistance increases rapidly with increasing magnetic field strength.

As is clear from the above principle, this property is determined by the absolute value of the magnetic field strength without depending on the direction of the applied magnetic field because the crystal 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 an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a superconducting magnetoresistive element including a pair of current electrodes 21 and 21 provided at both ends of the ceramic superconductor 3 and voltage electrodes 22 and 22 provided near the electrodes 21 and 21, On the superconducting magnetoresistive element 1, a control line 5 having a U-shape is formed via an insulating film 10.

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

First, in order to manufacture a magnetoresistive element of a ceramic superconducting film used in this apparatus, in the film forming apparatus outlined in FIG. 9, the substrate 7 was stabilized zirconia (YSZ) and the heater 9 was used to adjust the substrate temperature. While maintaining at 400 ℃, Y (N
_{O 3) 3 · 6H 2 O} , Ba (NO 3) 2, Cu (NO 3) the _{2 · 3H 2 O Y 1 Ba} 2 Cu
_A predetermined amount of ₃ O ₇ -x is weighed, and an aqueous solution of nitrate dissolved in water is intermittently sprayed from the jetting device 11 toward the substrate 7 so as to form a uniform film having a film thickness of 5 μm, and heat is applied. Decompose and oxidize to form a ceramic film, then 950 ℃ for 60 minutes and 500 ℃
It was annealed in air for 10 hours. The resistance of the ceramic superconductor film manufactured in this way begins to drop from 100k, and it shows zero resistance at 83k.

Next, this ceramic high-temperature superconductor film is 50 μm wide and long.
In order to form the superconductor 3 by processing it to 30 mm, a resist was applied and processed into a thin stripe shape by an ordinary photolithography process to produce the superconductor portion 3 of the superconducting magnetoresistive element 1. This ceramic high temperature superconductor could be easily processed with a phosphoric acid-based etching solution.

An insulating film made of polyimide resin on the superconductor 3.
After forming 10, the electrodes 21 and 22 and the control line 5 for generating a magnetic field are formed. Then, a wiring pattern of the Ti vapor deposition film is formed again by the photolithography process and the lift-off method of the Ti vapor deposition film. The ceramic superconducting device of the present invention shown in the figure was produced.

Ceramic superconducting magnetoresistive element 1 used in this example
Is considered to be an assembly of Josephson couplings because the insulating layer and the point contact interposed in the grain boundary are weakly coupled, and the relationship between the applied magnetic field and the element resistance is from the state of zero resistance as shown in FIG. The resistance suddenly appears in the magnetic field, and the rate of change of the resistance is extremely large. Further, the magnitude (threshold value) of the magnetic field where the resistance suddenly appears and the resistance increase rate can be controlled by the magnitude of the constant current flowing through the ceramic superconducting magnetic sensor 1.

When a current of 10 mA is applied to a straight Ti conductor wire, the magnetic field strength at a distance of about 50 μm from the conductor wire is about 0.4 gauss. From the characteristic graph of the superconducting magnetoresistive element shown in FIG. 2, it was found that the strength of this magnetic field was 20 μV when a constant current of 2 mA was applied to the ceramic superconducting magnetoresistive element.

From the above experiment, in the first embodiment, the control line 5 has a width of 30 μm and a thickness of 1 μm as shown in FIG.
The center-to-center distance between the superconducting magnetic sensor 1 and the parallel part was set to 50 μm. The thickness of the insulating film 10 was about 1 μm.

In the above configuration, when at least the superconducting magnetic sensor 1 is cooled to a temperature of 83k or less, no current is passed through the conductor 5 and no magnetic field is applied to the superconducting magnetoresistive element 1, through the terminals a and b. Even if a current of about mA is applied to the sensor 1, it is still in a superconducting state. Therefore, by passing a constant current I of 5mA through the conductors via terminals e and f, the magnetic field created by that current breaks the superconducting state of the superconductor 3. As shown in FIG. 3, an output voltage of 20 μV was obtained between the terminals c and d with a delay of about 0.5 picoseconds corresponding to the current I as shown in FIG. At this time, the constant current between the terminals a and b passed through the superconducting magnetoresistive element 1 was 2 mA.

In the superconducting magnetic sensor provided with the control line of the previous application Japanese Patent Application No. 63-29526, the control line is linear and the center distance from the element is 50 μm. 20mA for superconducting magnetoresistive element 1
When the output voltage is 20μV by applying the constant current of
It was necessary to pass a current of 10 mA through the straight parallel control lines. However, when the U-shaped laminated control line of the present invention is used, the magnetic field generated by the current converges on the superconducting magnetoresistive element 1, so control is performed. Apply a current of 5mA to line 5 and connect element 1 to 20.
This means that the output voltage of μV can be obtained and the input current can be reduced to half.

The second embodiment shown in FIG. 4 has a U-shape in which a pair of current electrodes 21 and a pair of current electrodes 21 and voltage electrodes 22 are partially laminated on the magnetoresistive element 1 of the superconductor 3 with an insulating film 10 interposed therebetween. Of the control line 5 and the control line 6 arranged in parallel to the superconductor 3 of the control line 5, and is formed on the substrate 7 by using a film forming technique.

Where the control lines 5 and 6 and the superconductor in FIG. 4 are parallel to each other, the center-to-center distance between them is 50 μm, and the line width of each is 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 described above, a current of 20 mA had to be applied to the control line 6.

Further, the currents I ₁ and I ₂ flowing in the control lines 5 and 6 are in the same direction, and the magnetic field acting on the superconductor 3 by the current I ₁ flowing in the control line 5 is H ₁ and the current I ₂ flowing in the control line 6 is By superconductor 3
Let H _{2 be} the magnetic field that acts on H, and let H _{0 be} the critical magnetic field of the superconducting magnetic sensor 1 when a predetermined constant current is flowing. H ₁ <H ₀ , H ₂ <H ₀ , H ₁ + H ₂ > H ₀ . Under the condition (1), the output voltage is generated between the terminals c and d as shown in FIG. 5 only when the currents flow through the control lines 5 and 6 at the same time, and it becomes the AND logic output. For example, when a current of 3 mA as I _{1 and} a current of 15 mA as I ₂ is applied to conductors 5 and 6, respectively, the current I ₁
An output voltage of 20 μV or more was obtained between the terminals c and d only during the period when I ₂ and I ₂ were flowing simultaneously.

Further, under the condition of H ₁ > H ₀ , H ₂ > H ₀ , | H ₁ −H ₂ | <H ₀ (2), the current I flowing through the control line 5 and the control line 6 as shown in FIG. _When the directions of ₁ and I ₂ are reversed, the output voltage is obtained between the terminals c and d only during the period when only _one of the currents I ₁ and I ₂ exists between the terminals c and d as shown in FIG. And the logical output of exclusive or was obtained. Also, under this current condition, an OR logic output is obtained by causing the currents I ₁ and I ₂ to flow in the same direction.

Although the current values I ₁ and I ₂ are appropriately selected in the above-described embodiment, the present invention is not limited to this, and for example, the current may be applied to the control lines 5 and 6. The current values I ₁ and I ₂ are set to constant values, the interval between the superconductor 3 and the control line 5 or the control line 6 is appropriately selected, and the control line 5 and the control line 5 are placed at positions satisfying the above formula (1) or (2). 6 may be provided.

Further, when the device of the present invention is manufactured, the method is not limited to the above-mentioned method, and the control lines 5 and 6 or the superconducting magnetic sensor 1 may be formed by a thin film by sputtering, MOCVD, electron beam evaporation, or the like. The result can be obtained, and the miniaturization of the processed shape can be expected.

The ceramic high-temperature superconductor film used in the examples of the present invention was Y ₁ Ba ₂ Cu ₃ O ₇ -x, but other Bi-Sr-Ca-Cu-O may be used as long as it has grain boundaries. System or Tl-Ca-Ba-
Needless to say, the same result can be obtained by using a high temperature superconductor having a component such as Cu-O.

Further, the positional 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 lines 6 may be arranged parallel to the superconductor 3 as shown in the figure, or may be laminated on the control lines 5.

As described in the above embodiment, if the control lines are laminated or the shape is U-shaped, the magnetic field due to the current in the vicinity of the element is converged inside the U-shape and is smaller than that of the linear control line. A magnetic field having the same strength can be applied to the ceramic superconductor by an electric current, and an efficient control line can be obtained.

By further thinning the ceramic superconducting film having grain boundaries, the control magnetic field can be reduced and a larger output voltage can be obtained.

Further, if the control line is arranged close to the superconductor via the thin insulating film, the magnetic field generated by the current of the control line can effectively act on the superconductor.

By combining the above improvements, a magnetic field due to a small amount of control line current can be effectively applied to the superconductor to perform various logical operations at high speed, and a ceramic superconducting device having a practical output level can be obtained. .

In addition, thinning, miniaturization, and reduction of the control line current reduce magnetic noise to the surroundings, enabling high-density integration.

<Effects of the Invention> As described above, according to the present invention, a weak bond that naturally intervenes at a grain boundary of a ceramic superconductor is used without using a Josephson junction for artificially producing an extremely thin insulating layer as in the conventional case. It is used to perform a logical operation using the superconducting magnetoresistive effect, and it is possible to efficiently operate a device having a practical output voltage and an extremely high operating speed peculiar to superconductivity.

Further, as described in the embodiments of the present invention, the control line is partly laminated on the superconductor via the insulating film or is U-shaped, so that the magnetic field due to the current of the control line is converged on the superconductor. Therefore, it is possible to operate with a small input current.

Furthermore, the control lines can be arranged in a plane as described in the embodiments, or the control lines can be easily formed into a multi-layer by an insulating film of a resin such as polyimide or an oxide such as SiO ₂ .
The device can efficiently perform various logical operations at high speed.

[Brief description of drawings]

FIG. 1 is a plan view showing the structure of an embodiment of the ceramic superconducting device of the present invention, FIG. 2 is a view showing an example of the characteristics of the ceramic superconducting magnetoresistive element, and FIG. FIG. 4 is a diagram showing the output response of the resistance element, and FIG. 4 is a plan view showing a structure in the case where a plurality of control lines for generating a magnetic field are provided in the other embodiment of the ceramic superconducting device of the present invention and the current directions are the same. 5 and 5 are views showing the relationship between the output response and the control line current in the case where the control lines have the same current direction according to the configuration of FIG. 4, and FIG. 6 shows the magnetic field in another embodiment of the present invention. FIG. 7 is a diagram showing a configuration in which the current directions of the two control lines generated are opposite to each other, and FIG. 7 shows the relationship between the output response of the device of the present invention having the configuration of FIG. 6 and the waveform of the current flowing through the control line. 8 and 9 show the ceramic superconducting device of the present invention. FIG. 9 is a plan view showing the structure of another embodiment, FIG. 9 is a view showing the schematic structure of a ceramic superconducting film manufacturing apparatus used for manufacturing the apparatus of the present invention, and FIG. 10 is a graph showing characteristics of the superconducting magnetoresistive element. FIG. 11 is a diagram showing an example, and an equivalent circuit of a superconducting magnetoresistive element. 1 …… Superconducting magnetoresistive element, 21,21 …… Current electrode, 22,22
...... Voltage electrode, 3 ...... Superconductor, 5,6 ...... Control line, 7 ......
Substrate, 10 ... Insulating film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Nojima Hideo Nojima 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (56) References JP-A-62-115881 (JP, A) JP-A-59 -17175 (JP, A)

Claims (4)

[Claims] 1. A ceramic superconducting element having at least a pair of electrodes, which exhibits a magnetoresistive characteristic by breaking a weakly coupled superconducting state of crystal grain boundaries by an extremely weak magnetic field, and a conductor provided in proximity to the ceramic superconducting element. The control line for controlling the conductivity of the ceramic superconducting element by the action of the magnetic field generated by the current flowing through the conductor, at least a part of which has a laminated structure with a thin insulating film interposed therebetween. Ceramic superconducting device. 2. The ceramic superconducting device according to claim 1, wherein the control line has a U-shaped folded shape, and a magnetic field generated in the conducting wire on each side by an electric current acts on the ceramic superconducting element. 3. The ceramic superconducting device according to claim 1, wherein the ceramic superconducting element is provided with two or more control lines capable of controlling individual currents. 4. The ceramic superconducting device according to claim 1, wherein the ceramic superconducting element is made of a film-shaped ceramic superconductor formed on a non-magnetic substrate.