JPH07169018A - Magnetic head - Google Patents

Abstract

PURPOSE:To obtain a magnetic head having a constitution which can improve both of the reproducing efficiency and the recording efficiency of a magnetic head in a short wavelength range by narrowing a gap. CONSTITUTION:A layer-built element which composed of a ferroelectric thin film 33 and conductor thin films 32 and 32 between which the thin film 33 is sandwiched is provided in the magnetic gap 3 of a magnetic core composed of core halves 1 and 2. A voltage is applied between the conductor thin films 32 and 32 which are used as electrodes through lead wires (not shown). The thickness of the ferroelectric thin film 33 is increased by a piezoelectric effect caused by the voltage application to increase the gap width of the magnetic gap 3. Moreover, a pressure produced by the increase of the thickness of the thin film 33 is applied to the butting parts of the magnetic core which face the magnetic gap to decline the permeability of those parts substantially and the gap width is practically increased further. That is, the gap width can be varied by the existence of the voltage application and the magnitude of the applied voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head for magnetically recording / reproducing information on / from a magnetic recording medium, and particularly to an induction device constructed by winding a winding coil around a magnetic core having a magnetic gap. Type magnetic head.

[0002]

2. Description of the Related Art The structure of a conventional magnetic head of this type is shown in FIG.
Will be described. In FIG. 1, reference numerals 1 and 2 denote core halves forming a magnetic core, which are made of a soft magnetic material and whose upper surface in the drawing is formed as a medium sliding surface 7 on which a magnetic recording medium (not shown) slides. It The core halves 1 and 2 are butted against each other, and are made of a low melting glass 4 and 6 arranged in a track groove 8 formed on the medium sliding surface 7 and defining a track width, and a groove 9 formed below the butted surface. They are joined by welding to form a magnetic core. A magnetic gap 3 is formed between the upper ends of the core halves 1 and 2 facing the medium sliding surface 7 of the abutting surfaces. Then, the winding coil 5 is wound around the magnetic core through the winding groove 10 formed in one core half 2 to form a magnetic head.

In such a conventional magnetic head, the magnetic gap 3 is made of a non-magnetic material such as SiO2 or Cr2O3 as a thin film having a predetermined thickness as shown in FIG. 2, and is used as a magnetic recording medium such as a magnetic tape. It has been ideal that the gap width of the magnetic gap 3 is always constant even by sliding.

[0004]

In short-wavelength recording such as VTR using the magnetic head as described above, the S / N ratio of the reproduced signal and noise of the shortest recording wavelength is S / N of the demodulated video.
Since it can be considered that the magnetic field is determined, the gap width of the magnetic gap is set so as to maximize the reproduction output at the shortest recording wavelength. That is, the gap width is the shortest recording wavelength ×
It is set to (about 1/4).

Further, in order to increase the recording density, the recording wavelength becomes shorter and shorter, and the gap width becomes narrower accordingly.
The coercive force of the magnetic tape is increasing more and more so that the required reproduction output can be obtained even at a short wavelength. For example, in the case of 8 mm VTR, the shortest recording wavelength is about 0.5 μm, so the gap width that maximizes the reproduction output is extremely narrow at 0.125 μm. In the future, as the recording density is further increased, the recording wavelength will become shorter, the gap width will become narrower accordingly, and the coercive force of the magnetic recording medium will also become larger.

Now, the relationship between the gap width of the magnetic head and the recording efficiency will be described with reference to the equivalent circuit of the magnetic head shown in FIG. In FIG. 3, Rg is the magnetic resistance of the magnetic gap, Ryo is the magnetic resistance of the yoke portion (magnetic material portion) of the magnetic core, Ra is the magnetic resistance from the magnetic gap tip of the magnetic head to the magnetic tape surface, and V is Magnetomotive force due to winding coil,
Φ is a magnetic flux flowing through the yoke portion, Φg is a magnetic flux flowing through the magnetic gap, and Φa is a magnetic flux flowing through the magnetic resistance Ra. From this equivalent circuit, Φa = Rg × V / [Ryo + Rg × (Ryo + Ra)].

A graph of the above equation is shown in FIG. From this graph, Φa becomes smaller as Rg becomes smaller.
That is, if the gap width is narrowed, the recording efficiency becomes poor.

As described above, as a major problem, when the gap width (about 1/4 of the shortest recording wavelength) is determined in consideration of the reproduction output, the gap width becomes narrower, while when the gap width becomes narrower, the recording efficiency becomes poor. However, recording on the magnetic recording medium cannot be performed sufficiently. This is a major obstacle to high density recording in magnetic recording.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic head of this type, which can improve the reproducing efficiency in the short wavelength region by narrowing the gap and the recording efficiency.

[0010]

In order to solve the above-mentioned problems, according to the magnetic head of the present invention, a ferroelectric thin film and a two-layer non-contact sandwiching the thin film are provided in the magnetic gap of the magnetic core. A magnetic conductor thin film is laminated to form a film, and the ferroelectric thin film and the conductor thin film are arranged so that the thickness direction thereof is the gap width direction of the magnetic gap, and the conductor thin film is used as an electrode to form the conductive film. By applying a voltage to the body thin film, the thickness of the ferroelectric thin film is increased by the piezoelectric effect.

[0011]

With this structure, when a voltage is applied to the conductor thin film, the thickness of the ferroelectric thin film increases, so that the gap width of the magnetic gap becomes wider. In addition, the pressure due to the increase in the thickness of the ferroelectric thin film is applied to the abutting surface portion facing the magnetic gap of the magnetic core, and the magnetic permeability of that portion is significantly reduced due to the stress, which further reduces the gap width. Increase to. That is,
The gap width can be changed depending on whether or not the voltage is applied and the height of the applied voltage.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 illustrates the structure of a magnetic head according to an embodiment of the present invention. The magnetic head is cut along the medium sliding direction perpendicularly to the medium sliding surface so as to divide the track width into two equal parts. It shows the state.

As shown in FIG. 5, core halves 1 and 2 made of a soft magnetic material are butted against each other, and a track groove 8 is formed on the medium sliding surface 7 and a groove 9 is formed below the butted surface. The low-melting-point glasses 4 and 6 arranged in the above are joined by welding to form a magnetic core. A magnetic gap 3 is formed between the upper ends of the core half bodies 1 and 2 facing the medium sliding surface 7 of the abutting surfaces. Then, the winding coil 5 is wound around the magnetic core through the winding groove 10 formed in one core half 2 to form a magnetic head.

The basic structure described so far is the same as that of the conventional example described above, but the structure of the magnetic gap 3 is different from the conventional one. The structure is shown enlarged in FIG.

As shown in FIG. 6, the magnetic gap 3 is composed of a stack of five thin films. On the outermost side, that is, on both sides in contact with the abutting surfaces of the core halves 1 and 2, a non-magnetic insulating thin film 31 made of SiO2 or Cr2O3,
31 is deposited. Non-magnetic conductor thin films 32, 32 made of gold, copper, aluminum, ITO (indium tin oxide) or the like are formed inside the thin films 31, 31, respectively. Further, sandwiched between the thin films 32, 32, a ferroelectric thin film 33 made of, for example, a PZT type ferroelectric is formed. These thin films are sequentially formed on the abutting surfaces of the core halves 1 and 2 by sputtering or the like in the manufacturing process of the magnetic head, and the total thickness thereof is the gap width of the magnetic gap 3.
That is, the thickness direction of each thin film is the gap width direction.

Further, a lead wire (not shown) is connected to the conductor thin films 32, 32, and a voltage can be applied to the thin films 32, 32 as electrodes. When a voltage is applied, the electric field causes the ferroelectric thin film 33 to expand in the thickness direction due to the piezoelectric effect, and the thickness increases,
When the application of voltage is stopped, it contracts and returns to the original thickness. In other words, the conductor thin films 32, 32 and the ferroelectric thin film 33 form a piezoelectric element.

With such a structure, the conductor thin films 32, 3
When a voltage is applied to 2, the thickness of the ferroelectric thin film 33 increases, and the gap width of the magnetic gap 3 becomes wider accordingly. Further, the pressure due to the increase in the thickness of the thin film 33 is applied to the abutting surface portion of the core halves 1 and 2 facing the magnetic gap 3, and the magnetic permeability of that portion is significantly reduced due to the stress, whereby the gap width is reduced. Further increased substantially.

By thus applying the voltage to the conductive thin films 32, 32, the gap width of the magnetic gap 3 can be increased, and the gap width can be variably controlled by the height of the applied voltage. .

According to the magnetic head of this embodiment, no voltage is applied to the conductor thin films 32, 32 during reproduction, and the gap width of the magnetic gap 3 is set to be the original narrow width, which is 1 / the shortest recording wavelength. 4, recording can be efficiently performed, and a voltage can be applied to the thin films 32 and 32 at the time of recording to increase the gap width, thereby enabling efficient recording.
That is, it is possible to achieve both improvement in reproduction efficiency in the short wavelength region due to narrowing of the gap and improvement in recording efficiency, which have not been realized conventionally.

As another effective use, when the magnetic recording medium recorded by another device is reproduced instead of the self-recording reproduction and the shortest recording wavelength of the medium is long, the gap is adjusted according to the wavelength. Increasing the width enables efficient reproduction.

In the above embodiment, only one set of the laminated body of the ferroelectric thin film 33 and the conductive thin films 32, 32 constituting the piezoelectric element is provided in the magnetic gap 3, but it is also possible to provide a plurality of sets. To be

[0023]

As is apparent from the above description, according to the magnetic head of the present invention, in the magnetic gap of the magnetic core,
A ferroelectric thin film and two layers of non-magnetic conductor thin films sandwiching the thin film are laminated to form a film, and the thickness direction of the ferroelectric thin film and the conductor thin film is the gap width direction of the magnetic gap. Since the thickness of the ferroelectric thin film is increased by the piezoelectric effect by applying a voltage to the conductive thin film using the conductive thin film as an electrode, the presence or absence of the voltage application , And the width of the magnetic gap can be changed according to the height of the applied voltage, and the optimum gap width can be set for both recording and reproducing according to the recording wavelength, and both recording and reproducing can be performed efficiently and a narrow gap can be achieved. It is possible to obtain an excellent effect such that the improvement of the reproducing efficiency in the short wavelength region due to the realization and the improvement of the recording efficiency can both be achieved.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of a conventional magnetic head.

FIG. 2 is a perspective view showing a magnetic gap of a conventional magnetic head.

FIG. 3 is a circuit diagram showing an equivalent circuit of a magnetic head.

FIG. 4 is a graph showing a relationship between a magnetic flux Φa flowing from a magnetic gap tip of a magnetic head to a magnetic tape and a magnetic resistance Rg of the magnetic gap.

FIG. 5 is a perspective view showing a structure of a magnetic head according to an embodiment of the present invention and showing a state cut perpendicularly to a medium sliding surface.

FIG. 6 is a perspective view showing a structure of a magnetic gap of the magnetic head.

[Explanation of symbols]

 1, 2 core half body 3 magnetic gap 4, 6 low melting point glass 5 winding coil 7 medium sliding surface 8 track groove 10 winding groove 31 insulator thin film 32 conductor thin film 33 ferroelectric thin film

Claims (2)

[Claims] 1. A ferroelectric thin film and two non-magnetic conductive thin films sandwiching the thin film are laminated to form a film in a magnetic gap of a magnetic core, and the ferroelectric thin film and the conductive thin film are electrically connected to each other. The ferroelectric thin film is arranged so that the thickness direction of the body thin film is the gap width direction of the magnetic gap, and a voltage is applied to the conductor thin film by using the conductor thin film as an electrode to reduce the thickness of the ferroelectric thin film by a piezoelectric effect. A magnetic head characterized by increasing the number. 2. The magnetic head according to claim 1, wherein an insulator thin film is formed by laminating each of the two conductor thin films on the outer side.