JPH0551961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic head for efficiently recording and reproducing high frequency signals, which is suitable for systems handling high frequency signals such as high-quality VTRs and digital VTRs.

BACKGROUND ART Conventionally, in devices for recording and reproducing high frequency signals such as VTRs, ferrite materials with low high frequency loss have generally been used as magnetic materials for video heads. However, in recent years, the development of systems that handle wider band signals, such as high-definition VTRs and digital VTRs, has become active.
In order to record such large amounts of information, recording media are also shifting from iron oxide based media to high coercive force media such as alloy powder media and metal evaporated media. On the other hand, the maximum magnetic flux density of a ferrite head is about 5000 Gauss at most, and in order to efficiently reproduce short wavelength signals, it is necessary to have a narrow gap. With anti-magnetic media, the ferrite core at the tip of the gap becomes saturated, making it impossible to record adequately.
Therefore, magnetic heads using metallic magnetic materials such as sendust alloys and amorphous magnetic alloys with high maximum magnetic flux density are being developed, but using bulk metallic magnetic materials suffers from large high frequency losses due to eddy currents. It cannot be used with the above systems. For this reason, in order to suppress the above-mentioned loss as much as possible, it is being considered to use a thin film of metal magnetic material. For example, by constructing the main magnetic circuit with a laminate of a metal magnetic thin film and an insulating thin film, it is possible to cope with high frequencies. It's on.

Problems to be Solved by the Invention The recording signal band of high-quality VTRs and digital VTRs reaches 30 to 60 MHz, and core materials for magnetic heads are required to have high initial magnetic permeability in such high frequency bands. . Figure 2 shows CoNbTaZr
This figure shows the frequency characteristics of the initial magnetic permeability of a laminate of an amorphous magnetic thin film and a SiO ₂ film. The thickness of the magnetic thin film per layer was 4 μm in consideration of eddy current loss, and the SiO ₂ film thickness between layers was 0.2 μm, and five layers were laminated. The figure shows an unoriented laminated film, and the eddy current loss is improved due to the lamination effect, but its high frequency characteristics are limited by Snook's limit line due to ferromagnetic resonance, and the initial permeability in the high frequency band of 30MHz or higher will be less than 500. Therefore, if such a non-oriented magnetic thin film is used as a head core, it cannot be applied to the above-mentioned high frequency system. On the other hand, the initial magnetic permeability characteristic of a multilayer film in which amorphous magnetic thin films with uniaxial anisotropy are laminated with their easy axes aligned is that the initial magnetic permeability is extremely low in all frequency bands when measured in the easy axis direction. On the other hand, when measured in the difficult axis direction, it maintains a high initial permeability up to high frequencies, and has a value of 1000 or more even at 60MHz. However, if a magnetic head with a relatively large winding window, such as a video head, is constructed using such a magnetic core having anisotropy in one direction, the magnetic path will include the easy axis direction, resulting in a decrease in head efficiency. There is a large decrease in Furthermore, it is extremely difficult to configure all magnetic paths in the hard axis direction from the viewpoint of the head manufacturing method.

Means for Solving the Problems In a magnetic head in which part or all of the magnetic path is formed by a multilayer magnetic core in which ferromagnetic thin films and insulating thin films are alternately laminated, the multilayer magnetic cores are anisotropic with respect to each other. A ferromagnetic thin film whose directions are substantially orthogonal and one of the easy axes of magnetization is configured to be substantially perpendicular to the sliding surface of the recording medium, and the direction of the easy axis of magnetization is substantially perpendicular to the sliding surface of the recording medium. The total thickness of the two ferromagnetic thin films is larger than the total thickness of the other ferromagnetic thin film.

Effect With the above configuration, the signal magnetization generated from the signal magnetization on the recording medium and taken into the magnetic head is
Near the magnetic gap, the thickness of the ferromagnetic thin film, which has a large initial magnetic permeability in the direction parallel to the recording medium sliding surface, is larger, so most of the magnetic flux flows in the direction parallel to the recording medium sliding surface rather than in the gap depth direction. . Therefore, leakage magnetic flux at the magnetic gap portion is relatively reduced, and the reproduction efficiency of the magnetic head is increased. On the other hand, in the magnetic path in the direction perpendicular to the sliding surface of the recording medium, the ferromagnetic conductive film with high initial magnetic permeability in the direction perpendicular to the sliding surface is thin, but the film width is wide, so it is sufficient to function as a magnetic path. The reluctance can be reduced, and the regeneration efficiency can be further improved. That is, since the magnetic head of the present invention can effectively utilize the characteristics of the hard-axis direction of the ferromagnetic thin film having the above-mentioned anisotropy in most of the magnetic paths,
A magnetic head capable of recording and reproducing signals with sufficiently high efficiency even at high frequencies of 30 MHz or higher can be obtained.

Embodiment A perspective view (partially cutaway view) of an embodiment of the present invention is shown in FIG. In the figure, 1 and 2 are made of ferromagnetic thin films such as amorphous alloys and Sendust alloys, and each has uniaxial anisotropy in the magnetic path plane. The easy axis is arranged so that the direction of the easy axis is substantially perpendicular to the recording medium sliding surface, while the easy axis of 2 is arranged in a direction that is substantially perpendicular to 1. These ferromagnetic thin films 1 and 2 are
A magnetic core 4 made of a multilayer film is constructed by laminating them with an insulating thin film 3 of SiO ₂ or the like interposed therebetween.
In addition, the film thickness per layer is less than the thickness considering eddy current loss in the frequency band used, and the total thickness of the ferromagnetic thin film 1 whose easy axis direction is almost perpendicular to the recording medium sliding surface is: It is configured to be larger than the total thickness of the other ferromagnetic thin film 2. A magnetic core 4 made of such a laminated film is sandwiched between non-magnetic substrates 5 such as barium titanate ceramics, and bonded to an opposing core having a winding window 6 through a bonding glass 7 to form a magnetic gap 8. There is.

According to the inventor's experiments, in a multilayer film in which amorphous magnetic thin films of the same thickness are formed so that their anisotropy directions are orthogonal to each other, the initial magnetic permeability characteristic measured in one of the anisotropy directions As shown in Figure 2,
Although it is about half of the value in the hard axis direction of a multilayer film with aligned anisotropic directions, its frequency characteristics are almost equal to those in the hard axis direction, and an initial permeability of more than 500 was obtained even at 60MHz. Furthermore, it was found that almost the same characteristics could be obtained by rotating the measurement direction by 90 degrees and measuring in the other anisotropic direction.

Furthermore, in another experiment, a video head was prototyped using an amorphous magnetic thin film having uniaxial anisotropy in the same direction as shown in Figures 3a and b, and the head output characteristics were measured, resulting in the results shown in Figure 4. The results were obtained. That is, the head a configured so that the axis of easy magnetization is perpendicular to the sliding surface of the recording medium obtained a considerably higher head output than the head b configured so that the axis of easy magnetization is parallel to the sliding surface of the recording medium. This is caused by the signal magnetization on the recording medium because the initial magnetic permeability in the direction perpendicular to the sliding surface of the recording medium near the magnetic gap, that is, in the direction parallel to the gap surface, is high in head b, as explained in the operation section. Most of the signal magnetic flux generated flows along the gap surface. Therefore, it is thought that the leakage magnetic flux at the magnetic gap increases and the regeneration efficiency decreases. On the other hand, in head a, the initial magnetic permeability in the direction parallel to the gap surface is quite small, and most of the signal magnetic flux flowing in from the tip of the gap flows in the direction parallel to the sliding surface, which has high initial magnetic permeability, so it flows into the gap surface. It is thought that the magnetic flux flowing along the magnetic gap is reduced, and therefore the leakage magnetic flux at the magnetic gap portion is reduced, and the regeneration efficiency is increased. This tendency can be clearly seen by looking at the magnetic flux line diagram calculated using the finite element method.

Figure 4c shows the head output characteristics of a video head in which the ferromagnetic thin film whose easy axis of magnetization is perpendicular to the sliding surface of the recording medium has a thickness of 3 μm, and the parallel ferromagnetic thin film has a thickness of 1 μm. This is what is shown. In the configuration of the present invention, as described above,
In the vicinity of the magnetic gap, the ferromagnetic thin film 1 having a high initial magnetic permeability in the direction parallel to the sliding surface has an advantage in terms of cross-sectional area and is therefore dominant, reducing leakage magnetic flux and increasing regeneration efficiency. Furthermore, in the magnetic path section perpendicular to the sliding surface, since the width of the magnetic path is wide, the ferromagnetic thin film 2, which has a high initial magnetic permeability in the direction perpendicular to the sliding surface, is dominant even if the film thickness is thin. As a result, it is possible to effectively utilize the characteristics in the difficult axis direction in most of the magnetic paths, so that signals can be recorded and reproduced with sufficiently high efficiency even in the high frequency range of 30 MHz or higher.

In a method of manufacturing such a magnetic head, first, ferromagnetic thin films and nonmagnetic insulating thin films are alternately laminated on a nonmagnetic substrate by sputtering. At that time, the ferromagnetic thin film is sputtered in a fixed magnetic field, and by forming a laminated film while rotating the magnet position 90 degrees for each layer, the anisotropic directions as described above can be easily alternately orthogonally crossed. A multilayer film is obtained. By stacking a plurality of head substrates on which multilayer films have been formed in this way, bonding them with crystallized glass or the like, and cutting them, a core block in which the multilayer films and nonmagnetic substrates described above are alternately laminated can be obtained. Thereafter, the magnetic head shown in FIG. 1 can be manufactured through the same steps as in the conventional ferrite head manufacturing method.

Effects of the Invention According to the present invention, it is possible to easily obtain a high frequency magnetic head that can record and reproduce data with sufficiently high efficiency even in a high frequency band of 30 MHz or higher.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a magnetic head according to an embodiment of the present invention, FIG. 2 is a diagram showing the measurement results of the initial magnetic permeability characteristics of a ferromagnetic thin film depending on the direction of anisotropy, and FIG. FIG. 4 is a plan view showing an example of a video head constructed of a ferromagnetic thin film having uniaxial anisotropy; FIG. 4 is a diagram showing head output characteristics of the video head shown in FIG. 3 and a video head of an embodiment of the present invention; be. 1, 2...Ferromagnetic thin film, 3...Insulating thin film, 4...
...Magnetic core, 5...Nonmagnetic substrate, 8...Magnetic gap.

Claims (1)

[Claims] 1. In a magnetic head in which part or all of the magnetic path is constituted by a multilayer magnetic core in which ferromagnetic thin films and insulating thin films are alternately laminated, the anisotropy directions of the multilayer magnetic cores are substantially orthogonal to each other and The direction of one easy axis of magnetization is substantially perpendicular to the sliding surface of the recording medium, and the total thickness of the ferromagnetic thin film whose direction of the easy axis of magnetization is substantially perpendicular to the sliding surface of the recording medium is A magnetic head characterized in that the thickness is greater than the total thickness of the magnetic thin film.