JPH01201814A - Superconducting magnetic head - Google Patents

Abstract

PURPOSE:To realize the reproduction of even magnetic recording with high density by generating voltage change for flux change with a few quantity of squid element. CONSTITUTION:A magnetic substrate 10 as a lower magnetic layer consisting of MnZn ferrite, etc., a magnetic yoke 11 as an upper magnetic layer, a squid constituting film 12 consisting of a superconducting thin film as an upper superconductive layer, and a superconducting material 13 as a lower superconductive layer are provided, and the superconducting material 13 and the squid constituting film 12 are constituted so as to be circulated around the magnetic yoke 11, and they are Josephson-coupled via thin insulating layers 14a and 14b. The yoke 11 and the magnetic substrate 10 constitute a ring core, and the superconducting material 13 and the constituting film 12 constitute the squid element. When a current flows on the element, the voltage change appears on a terminal 15 corresponding to the magnetic flux of the magnetic yoke 11, and the voltage having a cycle of phi0 appears. The fluxed quantum phi0 is a quantity of magnetic flux of 2.07X10<-15> Wb, and any large magnetic flux can be measured by counting the peak of the voltage change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic head using a Squillad element made of superconducting material.

[Conventional technology]

Magnetic recording plays an extremely important role as a device for recording or storing information. Its importance is particularly significant in devices such as KVTRs, cassette tape recorders, floppy disk drives, and hard disk drives for computers. Furthermore, in a device that performs magnetic recording or reproduction, the magnetic head is an essential component along with the medium, and its quality directly affects the performance of the device.

A magnetic head is generally a ring-shaped magnetic material with a wire wound around it. This is almost common to all recording, reproducing, and erasing heads. The size changes with the frequency of the signal to be recorded or reproduced. For audio recorders, the head has a track width of several hundred microns and an area of 10 mm square, and for video recorders, the head has a track width of several hundred microns and an area of approximately 2 mm square. For hard disk drives for high-speed computers, it is several tens of microns or several hundred microns.
Generally, it has a cross-sectional area of m square.

In order to increase the capacity of magnetic recording devices, research and development efforts have been made to improve recording density. As a result of previous research, records have been found to be quite dense (0.
, 25 μm/bit). It is also believed that there are no technical problems with the erasing method.

A thin-film magnetic head is a conventional magnetic head developed for high-density, high-speed operation. The yoke/electrode material is manufactured using thin film deposition means and photolithography technology, which allows the head chip to be made smaller and the resonant frequency to be higher, resulting in higher density, higher speed, and higher efficiency. did it. Figure 4 shows 2 tracks (2 channels)
An example of the structure of a conventional thin film magnetic head is shown below. 1 is the board, 2
3 is a lower magnetic yoke, 3 is an upper magnetic yoke, 4 is a magnetic gap, and 5 is an electrode. This type of magnetic head has a smaller magnetic yoke that increases efficiency and increases the output.
It is possible to increase the performance by 2 to 5 dB compared to the bulk type ring-shaped magnetic head. An example of the performance of a two-channel head for video signals as an example of the current thin film head is as follows.

That is, the reproduction output is 89μVrmS, and the noise is 89nVr.
ms (△f = 10 KHz), C/N is 6.0
dB, track width is 60 μm, extreme wavelength is 0.8 μm,
The highest frequency is 7MHz, the relative speed is 5.5m/see,
The usable coating type metal media has an Hc of 145°θe,
The Br is 2500G.

At this time, since one wavelength is considered to be two bits, the area is 24 μm2 per IBit. Considering that the reproduction output is proportional to the area and the noise is proportional to the square root of the area, the output at the same recording density as 2.5 replays per bit of optical recording is 9.
5 μVrms, noise is 29 nVrms, C/
N is 50 dB (Δf=10KH2). It is clear from various measurement results that the noise level of 29 nvrms (Δf=lQKHz) at this time is lower than the noise level of the preamplifier of the head and the impedance noise of the thin film head itself. Therefore, the coated metal medium itself used here has the potential to obtain such a high C/N.

[Problem that the invention seeks to solve]

However, such high density cannot be achieved with a C/N of 5 Q dB. In order to reproduce the same recording density as optical recording, the thin film head must have approximately 30 turns without increasing the DC resistance, but in this case, 1
This results in a decrease in efficiency per turn, a decrease in resonance frequency due to an increase in impedance, an increase in the number of photolithography steps, and a decrease in yield. Another drawback is that multi-tracking becomes difficult. In the case of a bulk type head, the number of turns is as high as 60 turns, which causes problems such as an increase in the winding window, a drive due to a reduction in the resonance frequency, and a reduction in the frequency, and 60 turns is not realistic in the 7 MHz band.

As described above, although current recording media have memory retention capabilities, there is a problem in that they do not have a reproducing head for high-density recording. On the other hand, if the number of coil turns of the conventional head is increased, the reproduction sensitivity can be improved in principle, but the following problems arise. First, the resonant frequency decreases, and the usable band becomes narrower, making it impractical. Secondly, due to the increase in the coil window, head efficiency decreases, making it impossible to obtain the desired 8N ratio. Also, because the number of windings is large, it is susceptible to external noise. Furthermore, the yield will deteriorate, and multi-tracking, which is a feature of thin-film heads, will become difficult.
etc. are excited.

The present invention provides a magnetic head that uses squid elements to reduce noise and is capable of reproducing high-density magnetic signals recorded on current metal-coated magnetic media, for example, signals with a density 10 times that of optical recording. This is what we are trying to provide.

[Means for solving problems]

For this purpose, according to the present invention, a lower magnetic layer, a lower superconducting layer disposed on the lower magnetic layer, and a lower superconducting layer disposed on the lower superconducting layer and surrounding the lower superconducting layer together with the lower magnetic layer are provided. It has an upper magnetic layer constituting a ring-shaped magnetic core, an upper superconducting layer disposed on the upper magnetic layer and forming a squid element together with the lower superconducting layer, and a signal extraction conductive part electrically connected to the upper superconducting layer. A superconducting magnetic head is presented.

[Effect]

Since SQUID elements produce voltage changes in response to slight changes in magnetic flux, extremely high reproduction sensitivity can be obtained, making it possible to reproduce magnetic recordings with extremely high recording densities.

〔Example〕

Before describing embodiments of the present invention, a SQUID element (5QUID) will be briefly explained.

When superconductors are brought into contact via a thin insulating layer (several nanometers), interference current between the two is observed.

This contact area is called a Josephson junction. A device in which two semicircular arc-shaped superconductors are connected in a ring shape, a Josephson junction is used at the connection point, and a voltage can be applied to the Josephson junction is called a dc-squid device. In this case, even a slight change in the magnetic flux in the ring-shaped portion results in a voltage change. Detection sensitivity is 3X10-5φ0/~4■-1φa=2.07 x
l O-15wb is extremely expensive.

FIG. 1 is a diagram showing the structure of a magnetic head as a first embodiment of the present invention. In this figure, 10 is a magnetic substrate as a lower magnetic layer made of MnZn ferrite, etc.;
1 is a magnetic yoke as an upper magnetic layer for transmitting magnetic signals; 12 is a squid structure film made of a superconducting thin film as an upper superconducting layer; 13 is a lower superconducting layer formed in a magnetic substrate and embedded in a groove. It is a superconducting material. The superconducting material 13 and the SQUID component film are configured to orbit around the magnetic yoke 11, and both are covered with thin insulating layers (14a, 14b).
10-50A), Josephson coupling is established.

15 is a terminal for current supply and signal extraction, and is made of superconducting material or ordinary conductive material (Cu, AP, Au
, kl, etc.). In this figure, two tracks (
Although an example is shown (2 channels), as can be seen from the figure, the structure is simple and multi-track (multi-channel) is easy to implement. The current supplied from the terminal 15 passes through the grounded common electrode 16 to form a circuit. In the case of a multi-track head, superconducting material 13;
The terminal 16 is common. In this figure, the magnetic yoke 11
and the magnetic substrate 10 constitute a ring core, and the superconducting material 13
The SQUID component film 12 constitutes a SQUID element.

By passing a current through this element, a voltage change is caused at the terminal 15 in accordance with the magnetic flux φ of the magnetic yoke 11. The situation is shown in Figure 2. As shown in this figure, the voltage changes with a period of φ0. φ0 is called magnetic flux quantum, 2
．． The amount of magnetic flux is 07 x 1 o-15wb. Therefore, any large magnetic flux can be measured at the level of φ0 by counting the peak of this voltage change, and the period φ
In the range of 0, it generally has a resolution of 10-5φO/j. According to research by the inventors, coated metal magnetic media generates a magnetic flux of about 22φ0 from an optical recording area of 2.5 μm2. It can be seen that the above voltage resolution is sufficient for detection.Furthermore, it is understood that sufficient resolution is achieved even at a density 10 times that of optical recording.In the present invention, the superconducting material shown in this example Material is LaBa2Cu30
7; YBa2CuO7 ceramic or these KS
r-doped, and further Y-8c -Ba-8r
-Cu-Mn-0 series ceramics, ceramics in which rare earth elements are added to the above ceramics, and ceramics in which fluorine is added to the above ceramics are used. These ceramics exhibit superconductivity at room temperature, so they can be used as squid elements that operate at room temperature.
A high-sensitivity playback head is made. Furthermore, there are no special limitations as long as it is a superconducting material that operates at room temperature. Needless to say, a superconductor that operates at low temperatures requires a cooling device. Since such a structure requires fewer overall steps, it is possible to use a thin film head with multiple windings (for example, the one shown in Figure 4).
This makes it much easier to manufacture and allows for easier multi-tracking. In addition, since crosstalk in the case of multi-tracking is determined by the size of the magnetic material of the yoke, crosstalk can be easily reduced.

FIG. 3 is a diagram showing the configuration of a magnetic head as a second embodiment of the present invention. In FIG. 1, a groove is formed in the magnetic substrate 10 and filled with a superconducting material, but in FIG. 3, a superconducting member 20 is formed on the substrate 10 using a film formation 7 otrinography technique. Moreover, this superconducting member includes a substrate 10 and a yoke 11.
Another feature is that it forms a magnetic gap between them. In the case of such a shape, there is no need to process the substrate in advance and it can be manufactured through a photolithography process regardless of the groove position on the substrate, and the presence of superconducting material in the magnetic gap improves the playback efficiency of the head. Features such as: In addition, in the embodiment shown in FIG. 2, the superconducting layer M1
A terminal 15 for current supply and signal detection, which is electrically connected to the superconducting thin film, is made of the same material and in the same process as the superconducting thin film. Accordingly, the number of diagonals compared to the head shown in FIG. 1 is reduced, making it possible to reduce costs.

〔Effect of the invention〕

As explained above, according to the superconducting magnetic head of the present invention,
Since extremely high reproduction sensitivity can be obtained, it has become possible to reproduce even extremely high-density magnetic recording. In addition, since the number of winding patterns is small, it is resistant to external noise and the manufacturing process can be simplified. Furthermore, since the structure is simple, effects such as multi-channelization can be obtained easily.

[Brief explanation of the drawing]

1 is a diagram showing the configuration of a head as a first embodiment of the present invention, FIG. 2 is a diagram for explaining the output characteristics of the head in FIG. 1, and FIG. 3 is a diagram showing the configuration of a head as a first embodiment of the invention. FIG. 4 is a diagram showing an example of the configuration of a conventional thin film magnetic head. In the figure, 10 is a magnetic substrate as a lower magnetic layer, 11 is a magnetic substrate as an upper magnetic layer. yoke, 12 a superconducting film as an upper superconducting layer, 13 a superconducting material as a lower superconducting layer, 1
5 is a conductive terminal as a signal extraction section.

Claims (5)

[Claims] (1) A lower magnetic layer, a lower superconducting layer disposed on the lower magnetic layer, and an upper portion disposed on the lower superconducting layer and forming a ring-shaped magnetic core around the lower superconducting layer together with the lower magnetic layer. A superconducting magnetic head comprising a magnetic layer, an upper superconducting layer disposed on the upper magnetic layer and forming a squid element together with the lower superconducting layer, and a signal extraction conductive part electrically connected to the upper superconducting layer. (2) The superconducting magnetic head according to claim (1), wherein the signal extraction conductive portion is made of a superconducting material. (3) The superconducting magnetic head according to claim (1), wherein the lower superconducting layer is configured to serve as a magnetic gap of the ring-shaped magnetic core. (4) The superconducting magnetic head according to claim (1), wherein the lower superconducting layer is grounded. (5) a lower magnetic layer, a lower superconducting layer disposed on the lower magnetic layer, and a ring-shaped magnetic layer disposed in parallel on the lower superconducting layer, each surrounding the lower superconducting layer together with the lower magnetic layer; a plurality of upper magnetic layers constituting a core; a plurality of upper superconducting layers each disposed on the plurality of upper magnetic layers and forming a plurality of squid elements together with the lower superconducting layer; and each of the plurality of upper superconducting layers. A multichannel superconducting magnetic head having a plurality of electrically conductive parts for signal extraction.