JPH0664905B2 - Solid-state magnetic memory device and recording / reproducing method thereof - Google Patents

Description

The present invention relates to a memory device as an external storage device of a computer.

(Prior Art and Problems Thereof) Conventionally, magnetic disk devices have been the mainstream of external storage devices for computers. Since the magnetic disk device has a rotating mechanism, it has a drawback that the access time is long, and there is a problem in mechanical durability with respect to the disk and the head.

(Object of the Invention) An object of the present invention is to provide a solid-state magnetic memory device and a recording / reproducing method thereof in which the above-mentioned drawbacks are eliminated.

(Structure of the Invention) According to the present invention, a plurality of second stripe-shaped superconductors are formed on one main surface of a magnetic recording medium layer with an insulating layer interposed therebetween at predetermined intervals. A plurality of first striped superconductors are formed on the striped superconductor and on the main surface of the magnetic recording medium layer with an insulating layer interposed therebetween so as to intersect the second striped superconductor at a predetermined angle. The body is formed at a predetermined interval, and a plurality of stripe-shaped magnetoresistive effect elements are formed at a predetermined interval on the other main surface of the magnetic recording medium layer via an insulating layer, The magnetic recording medium layer has a structure in which a plurality of third stripe-shaped superconductors are formed at predetermined intervals on the main surface and the stripe-shaped magnetoresistive effect element with an insulating layer interposed therebetween. The intersection of the two striped superconductors and the third striped superconductor A solid magnetic memory element characterized in that an intersecting portion of a conductor and a stripe-shaped magnetoresistive effect element is located at a position opposed to each other through the magnetic recording medium layer, so as to intersect at a predetermined angle through an insulating layer. A recording current is passed through the formed first and second stripe-shaped superconductors to magnetize the magnetic storage medium formed in the vicinity of the intersection of the second superconductor to record information. A third stripe-shaped superconductor formed in such a manner as to intersect at a position opposite to the intersection at a predetermined angle through an insulating layer and the third stripe-shaped magnetoresistive element Recording of a solid-state magnetic memory element characterized in that a sense current is passed through a superconductor, a magnetic field is applied to a stripe-shaped magnetoresistive effect element, and the information is reproduced as a resistance change of the stripe-shaped magnetoresistive effect element. It is a raw way.

(Detailed Description of Configuration) FIG. 1 shows a basic configuration example of the element of the present invention. An example of a circuit of a recording and reproducing system in the case where a solid-state magnetic memory is constructed by using this basic configuration is shown in FIGS. 2 and 3, and the configuration of the memory will be described by using this.

As shown in FIG. 1, the solid-state magnetic memory device of the present invention includes a first stripe-shaped superconductor 2 and a second stripe-shaped superconductor that intersect with one main surface of a magnetic storage medium layer 5 with an insulating layer 3 interposed therebetween. A body 1 is formed. At the time of recording, an electric current is passed through the two stripe-shaped superconductors to magnetize the magnetic storage medium near the intersection of these two superconductors. On the other hand, a stripe-shaped magnetoresistive effect element 7 and a third stripe-shaped superconductor 8 are formed on the other main surface of the magnetic storage medium layer 5 so as to intersect each other with an insulating layer 12 interposed therebetween. At the time of reproduction, a sense current is passed through the third stripe-shaped superconductor to extract the magnetization information as a resistance change of the stripe-shaped magnetoresistive effect element 7.

Next, an example of the memory circuit configuration during recording will be described with reference to FIG.

The first striped superconductor 2 and the second striped superconductor are respectively the first switch group 20, 21, 22, 23, 24, 25.
And 26, 27, 28, 29. Switch 26,27,28,29
Are connected to the current sources 30 and 31, respectively, and are also connected to the first Y-axis address decoder 19. Switch 20,21,22,23,
24 and 25 are connected to the current source on the one hand and the data "1" on the other hand,
It is connected to the first X-axis address decoder through AND gates 47, 48, 49, 50, 51, 52 for selecting "0". The AND gates 47, 48, 49, 50, 51, 52 are connected to the CPU and the interface 14 via the data flip-flop 45. Also, the first X-axis address decoder 44 is
CPU via the Y-axis address register 46 and the first Y-axis address decoder 19 via the first Y-axis address register.
And interface.

Next, an example of the memory circuit configuration during reproduction will be described with reference to FIG. At the time of reproduction, the stripe-shaped magnetoresistive effect element 7 and the third stripe-shaped superconductor 8 formed on the magnetic storage medium layer 5 are used. As shown in FIG. 3, the third stripe-shaped superconductor 8 is connected to the current source 33 via the switches 32 and 34.
Connected to. The switches 32 and 34 are connected to the CP via the second Y-axis address decoder 35 and the second Y-axis address register 36.
It is connected to U and interface 14. On the other hand, the stripe-shaped magnetoresistive effect element 7 is connected to the switches 38, 39, 40, which are connected to the CPU and the interface 14 via the reproducing circuit system 43, and at the same time, the second X-axis address decoder. It is connected to the CPU and the interface 14 via 41 and the second X-axis address register 42.

The operation at the time of data recording will be described with reference to FIGS. 4 and 5 using the configuration diagram. The operation will now be described by taking as an example one of the orthogonal superconductors on the magnetic recording medium as shown in FIG. 4- (a). The magnetic characteristics (BH curve) of the magnetic recording medium are shown in FIG. 4- (b). In FIG. 4- (a), the first X-axis address register 46, the first X-axis address decoder 44, and the data flip-flop 45 are set by an instruction from the CPU and interface 14 in FIG. Switch group 20, 21, 22, 23, 24, 25 and the first X-axis current source 16, 17
And AND gate 47,48,49,50,51,52 Select one from ON
In this state, a current Ix (pulse or direct current) is caused to flow through the first (X-axis) stripe-shaped superconductor 2, and B of FIGS.
A magnetic field (magnetic field Hx smaller than Hc of the magnetic storage medium) by the current Ix is applied to the magnetic storage medium 5 on the −H curve. However, in this state, no data is recorded on the magnetic storage medium.
Next, when a current Iy is passed through the second stripe superconductor 1 which is orthogonal to the second stripe superconductor 1, the current Iy is applied as shown in 4- (c)-(i), and as a result, the combined magnetic field Ht of Hx and Hy is generated. The magnetic field is larger than Hc and has an angle of 45 ° with respect to the applied magnetic fields Hx and Hy.

Where the magnetic field Hy due to the current in the first striped superconductor
Is bent by the Meissner effect in the portion of the second striped superconductor, so it returns to the original position in the lower portion of the second striped superconductor, and the magnetic field on the storage medium is the second striped superconductor. Works as if there were no conductor. The synthetic magnetic field Ht magnetizes the magnetic storage medium 5 in a vector manner of Ht. In an attempt to calculate the magnetic field generated by the first striped superconductor.

Ampere's law of circular integration From the formula, the cross-sectional shape of the striped superconductor is 0.5 μm.
When the magnetic field on the magnetic storage medium is calculated assuming that the thickness of the insulating layer 3 is 0.1 μm and the currents flowing through the stripe-shaped superconductor are 200 mA and 300 mA, Hx = 800 when i = 200 mA.
When Oe and i = 300mA, Hx = 1200Oe is obtained. The current density at this time is J = 8 × 10 ⁷ A / cm ³ (i = 200 mA) and J
= 1.2 × 10 ⁸ A / cm ³ (i = 300mA), synthetic magnetic field Ht
Will be 1120 Oe and 1680 Oe. For example, using the NbCN superconductor according to the literature, since the critical current density ^{Jc = 10 1 0 A / cm} 3 is obtained, with respect to the high Hc medium (Hc = 600 to 800), it is possible to sufficiently record . Next, by reversing the current directions of the currents Ix and Iy, it is possible to obtain the magnetic field in the reverse direction of the synthetic magnetic field Ht as shown in FIGS. 4 (c)-(ii).

The synthetic magnetic field Ht magnetizes the magnetic storage medium 5 below the orthogonal points of the first and second striped superconductors orthogonal to each other in the opposite direction. If one direction (135 °) of the magnetization state corresponds to the data “1” and the opposite direction (−45 °) corresponds to the “0”, the first and second stripe-shaped superconductors (1 Information "1" and "0" can be recorded in the magnetic storage medium 5 below the orthogonal point of (2). The state of magnetization recorded in this way is shown in FIG.

Next, a method of reproducing the magnetization M recorded on the magnetic recording medium 5 will be described. The stripe-shaped magnetoresistive effect element 7 is present via the insulating layer 6 below the magnetic storage medium 5, and the stripe-shaped magnetoresistive effect element 7 is further provided below the stripe-shaped magnetoresistive effect element 7 via the insulating layer 12. There is a third stripe-shaped superconductor 8 orthogonal to the resistance effect element 7. Therefore, the magnetization M of the magnetic storage medium 5 is now + 135 ° with respect to the current vector I _MR flowing through the stripe-shaped magnetoresistive effect element 7 as shown in FIG. 6- (a). In this state, the magnetic field H _M given to the stripe magnetoresistive effect element 7 by the magnetic field generated from the magnetization M at the orthogonal point has an angle of −45 ° with respect to the current vector I _MR as shown in FIG. 6- (b). is doing. Here, when a sense current Ise (pulse) is passed through the third stripe superconductor 8, the sense magnetic field is generated by Ise in the same direction as the current vector I _{MR at a} point orthogonal to the magnetoresistive effect element 7.
When Hse is generated, the combined magnetic field of H _M and Hse that overcomes the demagnetizing field in the width direction of the MR stripe is in the H _M direction (−45
)) Approaches the direction of current vector I _MR .

Next, the magnetization at the orthogonal point on the magnetic storage medium 5 is shown in FIG.
When the magnetization state of the magnetic recording medium is opposite (corresponding to data “0”) as in (ii), the sense current Ise (pulse) is similarly passed to the third strike-like superconductor 8. Hse magnetic field is generated at a point orthogonal to and the combined magnetic field of H _M and Hse.
The angle of Ht becomes smaller than + 135 ° of H _M with respect to the current spectrum I _MR (Hs should be close to + 90 ° in Fig. 6- (C)).
Control e. Here, FIG. 7- (A) shows how the resistance R changes with the magnetic field H applied to the stripe-shaped magnetoresistive effect element 7.
Shown in.

In FIG. 7- (A), the current I _M of the magnetoresistive effect element 7
The direction of magnetization of the magnetic recording medium 5 is either −45 ° or + 135 ° with respect to the direction shown in FIG.
On the curve, point (a) at Θ = −45 ° corresponds to data “1”, and point (b) at Θ = + 135 ° corresponds to data “0”.
The resistance value itself remains unchanged at Θ = + 135 ° and -45 °.

In such a state, the third stripe-shaped superconductor 8
When a sense current Ise (pulse) is applied to the
When the induction magnetic field Hse by se is applied, point (a) in FIG. 7- (A) changes in the direction of the arrow, and the resistance value increases only when the current pulse of Ise is applied. Furthermore, FIG. 7-
For point (b) of (A) (corresponding to “0”), the resistance value R is
It decreases only when the current pulse of Ise is applied. Therefore, in order to convert each resistance change into a voltage, the pulse and data "1" corresponding to the data "1" are set by the circuit configuration as shown in FIG. 7- (b), as shown in FIG. 7- (C). A pulse corresponding to 0 "is obtained with the opposite polarity.

In this way, the data can be reproduced.

For example, in the case of Ni _{8 3} Fe _{1 9,} in T = 4.2 ° K MR element (specific resistance fo = 4.75Ω) has been obtained. Therefore, if the stripe width is 0.5 μm and the thickness is 0.05 μm, 1
The resistance R ₁ per bit is Therefore, the resistance change amount ΔR ₁ = 0.95 × with respect to this value R ₁ .
0.164 = 0.1558Ω.

Therefore, the current i flowing in the stripe-shaped magnetoresistive effect element 7 is
When i = 1mA, the playback output e becomes 0.1558mV,
When i = 2 mA, the reproduction output e becomes 0.3116 mV, so a sufficiently practical value can be obtained. Here, the resistance and voltage at both ends of the striped magnetoresistive element 7 are 48.3 KΩ and 48.3 V (i = 1 mA) and 96 V (i = 2 mA), which are practical values.

If this reproduction output is amplified by reproduction amplification 10, Θ = −45
For .DEG. And .THETA. = + 135.degree., A pulse as shown in FIG. 7- (C) is obtained.

Here, the striped superconductor is NbCN, the striped magnetoresistive element is Ni-Fe, NiCo, etc., and the insulating layer is Al.
_The substrate was polished with ₂ O ₃ , SiO ₂ , silicon nitride, etc.
Si is suitable. In addition, the solid-state magnetic memory device portion is formed by sputtering, ion milling, X-ray exposure (or optical exposure),
A thin film forming technique such as polishing can be used.

The stripe-shaped patterns formed on both main surfaces of the magnetic storage medium layer do not have to be orthogonal to each other. Further, the widths of the patterns may not all be the same.

Further, naturally, the magnetic storage medium portion on which the superconductor and the magnetoresistive effect element are formed and the necessary peripheral circuit portion are installed in an ultra-low temperature environment.

When a normal conductor is used instead of the striped superconductor with the above structure, the resistance becomes very large in a square with a cross section of 0.5 μm, and the current is 200 mA to 300 mA.
When flowing, there is a problem that the heat generation is large and the material is melted. Therefore, it is necessary to use a striped superconductor having a resistance of 0.

(Example) A solid-state magnetic memory device portion of an example of the present invention was formed as shown in FIG. Stripe width 0.5 μm on substrate 11
Of the third striped superconductor (NbCN) 8 is formed by film formation by the Sumpatta method and pattern etching by the ion milling method, and an insulating layer (SiO ₂ ) is formed on the third striped superconductor 8. It is formed by a sputtering method, and the steps on the surface of the insulating layer (SiO ₂ ) are eliminated by an etch back method using an ion milling method to flatten the surface, and then, on the insulating layer 12 (SiO ₂ ), A stripe-shaped magnetoresistive effect element 7 (NiFe) having a stripe width of 0.5 μm orthogonal to the stripe-shaped superconductor 8 is formed by film formation by sputtering and etching by ion milling. entire surface insulating layer 6 (SiO ₂₎ was formed by sputtering comprising, further after performing step difference cancellation, sputtering a magnetic storage medium 5 (CoPt) uniformly over the entire surface on the insulating layer 6 Formed by, magnetic insulating layer on the gas-storage medium 5 sputtering a second striped superconductors stripe width 0.5μm on the (SiO ₂₎ was formed by sputtering the insulating layer 4 1 (NbCN) Film is formed by a film-forming method and etching by an ion milling method, an insulating layer 3 is formed on the entire surface including the second stripe-shaped superconductor 1 by a sputtering method, and a second stripe is formed on the insulating layer 3. Stripe width of 0.5 μm so that it intersects with the superconductor
The first striped superconductor 2 (NbCN) was formed by sputtering and etching by ion milling. The superconductor portion thus formed was operated in a cryogenic state of about 4.2 ° K (liquid helium).

The distance between stripes of the stripe-shaped superconductor and the stripe-shaped magnetoresistive effect element 7 is 0.5 μm, and the thickness (t) is 0.5 μm (stripe-shaped superconductor) and 0.05 μm (stripe-shaped magnetoresistive effect). The stripe length (l) was set to 1 inch.

In this embodiment, one bit has a size of 1 μm × 1 μm, and an area density of 6.45 × 10 ⁸ bits square inch is realized. If the stripe width is further reduced, the capacity per square inch increases. Also, the bit size 1
In case of μm × 1μm, if you use 2.5 inch square substrate,
One board can have a memory capacity of about 1 gigabyte (GB).

(Effects of the Invention) As described above, the mechanical durability and the like required for the rotating mechanism and the disk head system of the conventional magnetic disk device are eliminated, and a large capacity (5 × 10 ⁸ bits / square inch or more) is obtained.
A non-volatile solid magnetic file memory was obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a solid-state magnetic memory device of the present invention. FIGS. 2 and 3 are diagrams showing an example of a circuit configuration at the time of data recording and reproduction, respectively, and FIG. 4 (a),
(B) and (c) are diagrams showing the principle at the time of recording, FIG. 5 is a diagram showing the magnetized state in which the magnetic storage medium is recorded, and FIGS. 6 (a), (b) and (c) are at the time of reproducing. Showing the principle of, No. 7
(A), (b), (c) is a figure explaining operation | movement of this invention. 1 is the second striped superconductor, 2 is the first striped superconductor, 8 is the third striped superconductor, 3, 4,
6, 12 and 13 are insulating layers, 5 is a magnetic storage medium, 7 is a striped magnetoresistive element, 9 is a resistor R, 43 is a regenerative amplifier, 11
Is a board, 14 is a CPU and an interface, 46 is the first x
Axis address register, 18 is first y-axis address register, 44 is first x-axis address decoder, 19 is first y-axis address decoder, 45 is data flip-flop, 4
7,48,49,50,51,52 are AND gates, 16,17,30,31 are current sources, 20,21,22,23,24,25,26,27,28,29 are first switches Group, 36 is a second y-axis address register (for reproduction), 42 is a second x-axis address register, 35 is a second y-axis address decoder, 41 is a second x-axis address decoder, and 43 is a reproducing circuit Reference numeral 9 denotes a resistor R, 38, 39, 40, 32, 34 denote second switch groups 33, and current sources, respectively. Further, in FIG. 2 and FIG. 3, the inner portion of the broken line shows the solid magnetic memory element portion.

Claims (2)

[Claims] 1. A plurality of second stripe-shaped superconductors are formed on one main surface of a magnetic storage medium layer with an insulating layer interposed at predetermined intervals. A plurality of first stripe-shaped superconductors are predetermined so as to intersect the second stripe-shaped superconductor at a predetermined angle on the conductor and on the main surface of the magnetic storage medium layer via an insulating layer. And a plurality of stripe-shaped magnetoresistive elements are formed at predetermined intervals on the other main surface of the magnetic storage medium layer with an insulating layer interposed therebetween. The first and second stripes have a structure in which a plurality of third stripe-shaped superconductors are formed at predetermined intervals on the main surface of the medium layer and on the stripe-shaped magnetoresistive effect element via an insulating layer. -Shaped superconductor intersection and third stripe-shaped superconductor Solid-state magnetic memory device characterized by intersection of the stripe-like magnetoresistive effect element is disposed at a position opposed through the magnetic storage medium layer. 2. A recording current is applied to first and second stripe-shaped superconductors which are formed so as to intersect each other at a predetermined angle through an insulating layer, and are formed in the vicinity of the intersection of the two superconductors. A third stripe shape formed so that the magnetic recording medium is magnetized to record information, and a position facing the intersection via the magnetic recording medium is an intersection, and the intersection is formed at a predetermined angle via an insulating layer. Of the superconductor and the stripe-shaped magnetoresistive effect element, a sense current is passed through the third stripe-shaped superconductor,
A recording / reproducing method for a solid-state magnetic memory element, characterized in that a magnetic field is applied to the stripe-shaped magnetoresistive effect element and the information is reproduced as a resistance change of the stripe-shaped magnetoresistive effect element.