JP2656485B2 - Magnetic head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head, and more particularly to an ultra-high sensitivity reproducing magnetic head using superconducting quantum interference.

[Prior Art] High-density magnetic recording has progressed remarkably, and in recent years, research on perpendicular magnetic recording suitable for high-density magnetic recording has been advanced. In conventional longitudinal magnetic recording, recording has also been improved by improving magnetic heads and recording media. Densification is progressing.

When linear recording density and track density are increased,
Since the area of the recording medium involved per pit or per wavelength decreases, the reproduction output decreases. It has been clarified that when recording is performed by perpendicular magnetic recording, a signal having a linear recording density of 500 KBPI can be recorded. But,
When the recorded signal is reproduced by a conventional magnetic head, the magnetic flux generated from the signal magnetization of the medium is weak, so that there is a problem that the output is significantly reduced as compared with a low recording density. (Proceedings of the 10th Annual Meeting of the Japan Society of Applied Magnetics (1989) p335) [Problems to be Solved by the Invention] The present invention solves such problems and reproduces recorded signals having extremely high linear recording density and track density. As you can
It is an object of the present invention to provide a reproducing magnetic head with extremely high sensitivity.

[Means for solving the problem]

In order to solve the above-mentioned problems, a magnetic head according to the present invention comprises at least a magnetic path for guiding a reproducing magnetic flux and a superconducting ring linking the magnetic path to form a superconducting quantum interferometer. That is, a superconducting quantum interferometer (abbreviated SQUID) is used as a means for detecting magnetic flux. A superconducting quantum interferometer utilizes a phenomenon in which a superconducting current flowing through a superconducting ring including one or two Josephson junctions changes according to the amount of magnetic flux passing through the ring, and the amount of magnetic flux is highly sensitive. An element to be measured.

Since this superconducting quantum interferometer utilizes a superconducting state, the device has to be made of a superconducting material, and the whole device has to be cooled to a very low temperature so as to be in the superconducting state. However, progress in research and development of superconducting materials in recent years has been remarkable, and materials that become superconducting at about 95 ° K have been found. By using such a high-temperature superconducting substance, it becomes possible to configure an ultra-sensitive reproducing magnetic head using a superconducting quantum interferometer.

[Action]

The magnetic head of the present invention comprises at least a magnetic path for guiding a reproducing magnetic flux and a superconducting ring linking the magnetic path to form a superconducting quantum interferometer. Further, by employing a configuration having a cooling element utilizing the Peltier effect, it is effective in efficiently cooling a necessary portion and maintaining a superconducting state. Further, a cooling part is separated from the recording medium facing surface of the head, and in order to facilitate the cooling, a normal coil which interlinks with a magnetic path for guiding a reproduced magnetic flux is provided once, and the coil is connected to the coil. Another intersecting magnetic path may be formed so that the magnetic flux of this magnetic path interlinks with the superconducting quantum interferometer element. In addition, in the case of this configuration, without forming another magnetic path, a coil that links with the magnetic path for reproduction magnetic flux and a magnetic flux that links the superconducting quantum interferometer element through the space can also be used. This is possible because of the high sensitivity of the superconducting quantum interferometer element.

In the magnetic head of the present invention, the shape of the magnetic path for guiding the reproduction magnetic flux may be a conventional ring type or a thin main magnetic pole film like a single pole type head for perpendicular magnetic recording.

In a conventional head, a coil having a large number of turns was required to improve the reproduction sensitivity. However, by adopting the configuration of the present invention, a ring using one superconducting material may be formed.
The advantage is that the process is greatly simplified.

The superconducting quantum interferometer used in the present invention includes a DC type including two Josephson junction elements and an AC type including one Josephson junction element. Since the direct current type needs to form two Josephson junctions, it is disadvantageous in process compared to the alternating current type including one Josephson junction,
There is an advantage that the circuit configuration is simple. On the other hand, the AC type only needs to form one Josephson junction, which is advantageous in the process, but has a complicated circuit configuration. Any type can be used for the magnetic head of the present invention, and each advantage can be selected and used.

The superconducting quantum interferometer used in the magnetic head according to the present invention has a problem that it is extremely sensitive to external magnetic flux, and thus is susceptible to leakage magnetic flux other than external signals, and noise such as electromagnetic waves. . In order to solve this point, it is desirable to provide a shield for the magnetic head of the present invention. As the shield material, a high magnetic permeability material such as a conventional Ni-Fe alloy (permalloy) or an amorphous alloy can be used. In addition, it is most preferable to use a superconducting material as a shielding material since there is an effect that magnetic flux does not penetrate into a superconducting material.

Further, in the magnetic head of the present invention, by providing a bias coil arranged so as to link the magnetic flux with the superconducting quantum interferometer element, and by passing an AC bias current to this,
It is also possible to make signal detection easier.

As the superconducting material used for the magnetic head of the present invention, for example, (Sr _x La _{1 -x} ) ₂ CuO ₄ (x = 0.05 to 0.1) or (B
A material having a composition such as a _1-x Yx) ₃ Cu ₂ O ₇ ( _{x to} 0.3) can be used. In particular, the latter is a preferable material because it becomes a superconductive state at a high temperature of 95 ° K.

Further, in the magnetic head of the present invention, by providing the recording coil in linkage with the magnetic path of the magnetic head, the magnetic head can be used as a conventional recording head. As the recording coil, the above-described bias coil or a high-frequency coil for signal detection used in an AC superconducting quantum interferometer can be switched to a recording film. By using a superconducting material as the material of this coil, heat generation due to the recording current can be minimized, and an excellent recording head can be obtained.

〔Example〕

Next, the magnetic head of the present invention will be described in detail with reference to examples.

FIG. 1 is an example of a head having a structure in which a portion of a superconducting quantum interferometer is separated from a recording medium facing surface. (A) is a plan view excluding a protective material, and (b) is a diagram showing a cross section taken along line AA ′ of (a). This head, like a normal ring-type head, allows a magnetic flux leaking from a recording medium to flow through a magnetic path composed of a substrate 1 and a magnetic pole 2 made of a magnetic material, and is temporarily converted into a signal current by a magnetic flux transfer coil 22 interlinking with the magnetic flux. Then, a magnetic flux is generated in a rear magnetic path composed of the rear substrate 23 and the rear magnetic pole 24 interlinking with the ring, and a ring 4 made of a superconducting material interlinking the magnetic flux is generated.
Is used to detect a signal. In this case, the portion made of the superconducting material can be separated from the portion in sliding contact with the recording medium, so that only the portion using the superconducting material can be easily cooled. In the example of the head shown in FIG. 1, a superconducting material is used by using a cooling element 26 using a Peltier effect or the like via a material 25 having good heat conduction in a portion using the superconducting material. The part can be cooled efficiently. In such a case, it is desirable that the substrate forming the front magnetic path and the substrate forming the rear magnetic path be separated using an insulating material 27 in order to thermally insulate the substrate.

FIG. 2 is an example in which the rear magnetic path of the head shown in FIG. 1 is omitted, and a coil for transmitting a reproduction signal and a superconducting ring are magnetically coupled through a space. Such a configuration is also possible because the superconducting quantum interferometer has extremely high magnetic flux detection sensitivity. In the heads shown in FIGS. 1 and 2, only an example of a DC superconducting quantum interferometer is shown, but as shown in FIG. 3, a head combined with an AC superconducting quantum interferometer is used. It is, of course, possible.

In FIG. 3, the superconducting ring 4 includes one Josephson junction 5, and further includes a high-frequency coil 10 for signal detection magnetically coupled to the superconducting ring.
The reproducing magnetic head equipped with such a superconducting quantum interferometer has a magnetic flux configured so that the reproducing magnetic flux penetrates the superconducting ring of the superconducting quantum interferometer. It has the feature that it can be detected with high sensitivity.

〔The invention's effect〕

As described above, the magnetic head according to the present invention can reproduce a very weak signal having an extremely high recording density with high sensitivity, and can obtain a magnetic head that is resistant to external noise and generates little heat during recording.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a magnetic head according to the present invention.
FIG. 3 and FIG. 3 are views showing another embodiment of the magnetic head of the present invention. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Magnetic pole, 3 ... Insulating material, 4 ... Superconducting ring,
5 ... Josephson junction, 6 ... Terminal part, 7 ... Insulation material, 8 ...
Recording medium facing surface, 9: protective material, 22: magnetic flux transmission coil, 23
... rear substrate, 24 ... rear magnetic pole, 25 ... thermal conductive material, 26 ... cooling element, 27 ... insulating material.

Continued on the front page (72) Inventor Takeo Yamashita 1-280 Higashi-Koigabo, Kokubunji-shi, Hitachi, Ltd. Central Research Laboratory, Ltd. Inventor Yoshinobu Tarutani 1-280 Higashi-Koigabo, Kokubunji-shi Inside Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-60-140164 (JP, A) JP-A-62-75954 (JP, A) JP-A-61-61 255077 (JP, A)

Claims (4)

(57) [Claims] A substrate; an insulating layer formed on the substrate;
A superconducting ring formed on the insulating layer and having a Josephson junction; and a magnetic pole formed on the insulating layer so as to interlink with the superconducting ring, one end of the magnetic pole facing the recording medium. A first magnetic path, a second magnetic path composed of a magnetic flux transmission coil interlinking with the first magnetic path, and a third magnetic path interlinking with the second magnetic path and the superconducting ring. Consists of roads,
The substrate includes a first substrate that forms a recording medium facing surface together with the first magnetic pole and is made of a magnetic material, a second substrate on which the superconducting ring is formed, and a first substrate and a second substrate. A third substrate for thermally insulating the substrate of
A magnetic head, wherein a cooling element for cooling the superconducting ring is formed above the superconducting ring. 2. The magnetic head according to claim 1, wherein said superconducting ring has two Josephson junctions. 3. The magnetic head according to claim 2, wherein a coil interlinking with said magnetic pole is further provided inside said superconducting ring. 4. The superconducting ring has one Josephson junction, and further includes a signal detection coil magnetically coupled to the superconducting ring. 2. The magnetic head according to claim 1.