JP2513206B2 - Composite magnetic head for overwriting - Google Patents

Description

The present invention relates to a composite magnetic head suitable for a so-called overwriting method used in a magnetic recording / reproducing apparatus such as a rotary head type digital audio tape recorder (R-DAT). In particular, the present invention relates to an overwriting composite magnetic head suitable for recording / reproducing of a high coercive force magnetic recording medium such as a metal tape.

[Outline of Invention]

The present invention relates to a composite magnetic head for overwriting, wherein a magnetic core half is composed of a composite magnetic material of an oxide magnetic material and a magnetic alloy thin film, wherein the magnetic alloy thin film and the oxide magnetic material in the vicinity of a magnetic gap are provided. And the saturation magnetic flux density Bs (kG) and the film thickness d (μ
In the area surrounded by four points (5.5,10), (7,10), (16,1), and (10,1) when the relationship of (m) is expressed in Cartesian coordinate system (Bs, d). By using the magnetic alloy thin film set to, it is intended to improve the recording / reproducing characteristics for the high coercive force magnetic recording medium, and to improve the productivity, mass productivity, and manufacturing yield.

[Conventional technology]

In the field of magnetic recording, high density recording and high quality recording have been pursued, and along with this, a so-called PCM (pulse signal modulation) recording system for converting an analog signal into a digital signal for recording has been developed. For example, a so-called R-DAT has been proposed in the audio field. Using this PCM recording system, low noise and high fidelity reproduction can be realized.

Normal recording (analog recording) with the PCM recording method
Compared with, the amount of recorded signals increases dramatically,
There is a demand for narrower head gap length and shorter recording wavelength. Further, a high coercive force is required for the magnetic recording medium, and for example, an alloy coating type so-called metal tape using ferromagnetic metal powder such as Fe, Co, Ni as magnetic powder has been developed and put into practical use. There is.

Therefore, in order to sufficiently magnetize such a magnetic recording medium, it is required for the core material of the magnetic head to have a sufficiently high saturation magnetic flux density commensurate with the coercive force of the medium. In particular, when recording and reproducing are performed by the same magnetic head, it is necessary that the material has not only the above-mentioned saturation magnetic flux density but also a sufficiently high magnetic permeability in the applied frequency band.

However, a ferrite head using an oxide magnetic material such as ferrite as the core material cannot handle the above high coercive force magnetic recording medium because of its low saturation magnetic flux density, and a magnetic alloy material such as Fe-Al-Si. A head using a system alloy material can record a high coercive force medium in a sufficiently high magnetic field because it has a saturation magnetic flux density approximately twice that of ferrite. The effective magnetic permeability in the band is low and the reproduction characteristics are deteriorated.

Under such circumstances, a so-called composite magnetic head has been developed in which a magnetic core half body is formed by using the composite magnetic material of the oxide magnetic material and the magnetic alloy thin film, and the abutting surface of these magnetic alloy thin films is a magnetic gap. Has been converted. This composite magnetic head exhibits excellent recording / reproducing characteristics with respect to the above-mentioned high coercive force medium because the magnetic gap is formed of a high saturation magnetic flux density material and the average magnetic permeability of the head is high.

In particular, a structure in which the magnetic alloy thin film is provided only near the abutting surface of the oxide magnetic material, and the boundary surface between the oxide magnetic material and the magnetic alloy thin film near the magnetic gap is substantially parallel to the magnetic gap surface. The composite magnetic head of 1 has the advantages that the track width can be set independently of the film thickness of the magnetic alloy thin film and that it has a simple structure similar to the conventional ferrite head. Excellent in terms of yield.

[Problems to be Solved by the Invention] In the composite magnetic head, when the productivity and mass productivity are taken into consideration, it is preferable that the thickness of the magnetic alloy thin film is smaller, but in consideration of recording characteristics. It is necessary to secure a certain thickness and saturation magnetic flux density.

That is, if the thickness of the magnetic alloy thin film is too small,
The original meaning of disposing the magnetic alloy thin film is diminished, and the recording ability to the high coercive force magnetic recording medium, especially the recording ability in the long wavelength band is deteriorated. It takes a lot of time, and the merits of productivity and mass productivity diminish.

Therefore, in the composite magnetic head having the above configuration,
While ensuring recording characteristics for high coercive force magnetic recording media,
Further improvement is desired in order to improve productivity and mass productivity.

Further, in a device for recording a digital signal such as the above R-DAT, a so-called overwriting recording system is adopted in which a new signal is written over the previous signal,
It does not have a dedicated erase head such as a video tape recorder (VTR). Therefore, for example, when a short wavelength signal (new signal) is recorded from a long wavelength signal (previous signal), the previous signal is not completely erased and so-called unerased occurs. This unerased signal appears as noise during reproduction, which causes deterioration of reproduction characteristics.
This improvement is also desired.

Therefore, the present invention has been proposed in view of such conventional circumstances, is excellent in recording ability for a high coercive force magnetic recording medium, and has no unerased signal before, and has excellent recording characteristics, Moreover, it is an object of the present invention to provide a composite magnetic head for overwriting that is excellent in productivity and mass productivity.

[Means for solving problems]

As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that there are optimum ranges for the film thickness and the saturation magnetic flux density of the magnetic alloy thin film depending on the signal recording method. In particular, in the composite magnetic head mounted in the above-mentioned overwriting type magnetic recording / reproducing apparatus, the magnetic alloy thin film serving as the main core material has its optimum thickness range naturally set by the saturation magnetic flux density of the thin film. By using the magnetic alloy thin film in the region in which the film thickness and the saturation magnetic flux density are related to each other, it has been found that the recording performance, productivity and mass productivity of the composite magnetic head can be simultaneously improved.

The present invention has been completed based on the above findings, and a pair of magnetic core halves composed of an oxide magnetic material and a magnetic alloy thin film are butted, and a magnetic gap is formed by the magnetic alloy thin films. A composite magnetic head in which a boundary surface between the oxide magnetic material and the magnetic alloy thin film in the vicinity of the magnetic gap is substantially parallel to the magnetic gap surface, and the saturation magnetic flux density Bs (kG) of the magnetic alloy thin film and When the relationship of the film thickness d (μm) is expressed in the Cartesian coordinate system as (Bs, d), it is (5.5,10), (7,10), (16,1), (10,1) 4
It is characterized in that it is set within an area surrounded by dots.

[Action]

Since the composite magnetic head for overwriting of the present invention has a structure in which the boundary surface between the magnetic alloy thin film and the oxide magnetic material in the vicinity of the magnetic gap is substantially parallel to the magnetic gap surface,
It can be manufactured with the same number of steps as a conventional ferrite head, and since the film thickness d (μm) of the magnetic alloy thin film is set within the range of 1 ≦ d ≦ 10, productivity and mass productivity are improved.

Further, in the present invention, the film thickness d of the magnetic alloy thin film is set from the relationship with the saturation magnetic flux density Bs of the thin film in consideration of the recording ability to the high coercive force magnetic recording medium. Can be sufficiently magnetized (recorded). In particular, the magnetic alloy thin film in the above region has a low recording output in the long wavelength band, and even if a short wavelength signal is recorded on it, noise due to so-called unerased signal is reduced.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

A composite magnetic head to which the present invention is applied is a recording / reproducing (or recording-only) mounted on a magnetic recording / reproducing apparatus to which an overwriting recording system by PCM recording corresponding to high density and high quality of recording is applied. It is a composite magnetic head for overwriting.

In the composite magnetic head for overwriting of this embodiment, as shown in FIGS. 1 (A) and 1 (B), the magnetic core portions (1), (11) occupying most of the magnetic core half body. Are made of an oxide magnetic material, and both sides thereof are cut out in a substantially arc shape in the vicinity of the contact surface by track width regulating grooves (2) and (12) for regulating the track width. In addition, the contact surfaces of the magnetic core portions (1) and (11) include the inner walls of the track width regulating grooves (2) and (12), and extend from the front gap forming surface to the back gap forming surface. Up to this, magnetic alloy thin films (3) and (13) made of a high saturation magnetic flux density alloy are adhered to form a pair of magnetic core halves (I) and (II).

Then, the two parallel portions of the magnetic core halves (I) and (II) are formed on the contact surfaces of the magnetic alloy thin films (3) and (13) through the gap film (23) having a predetermined film thickness l. (3a),
By abutting (13a) with each other, a magnetic gap g having a track width of Tw in FIG. 1 (B) is formed. In the overwriting composite magnetic head of the present embodiment, the magnetic gap g is inclined by a predetermined angle with respect to the direction orthogonal to the running direction X of the magnetic recording medium, which is suitable for a so-called azimuth recording system. .

Here, the film thickness l of the gap film (23) corresponds to the gap length of the composite magnetic head, and the film thickness l is appropriately set according to the purpose of use.

Non-magnetic materials (22), (22) for restricting the track width in the track width restricting grooves (2), (12) to prevent wear of the magnetic alloy thin films (3) (13). Is melt-filled. The magnetic core half (I) has a winding hole (21) for restricting the depth of the magnetic gap g and winding a coil.

In the composite magnetic head for overwriting having such a configuration, the track width Tw can be freely set without depending on the film thickness d of the magnetic alloy thin films (3) and (13). Therefore, the time required for forming the magnetic alloy thin films (3) and (13) can be freely set, which is extremely advantageous in terms of productivity and mass productivity.

Further, the composite magnetic head has a magnetic core portion (1),
The structure is almost the same as the conventional ferrite head except that the magnetic alloy thin films (3) and (13) are arranged on the contact surface of (11). It is also excellent in terms of manufacturing yield.

Here, a large recording magnetic field corresponding to a high coercive force magnetic recording medium corresponding to high density and high quality recording is generated,
In order to obtain a head which is not erased and which is also excellent in terms of productivity and mass productivity, in the present invention, the film thickness d and the saturation magnetic flux density Bs are used as the magnetic alloy thin films (3) and (13). Was used within a predetermined region (shown by the diagonal lines in FIG. 2).

Here, as the magnetic alloy thin films (3) and (13),
Fe-Ga-Si soft magnetic thin film, Fe-Al-Ge soft magnetic thin film, Fe-
Ga-Ge soft magnetic thin film, Fe-Si-Ge soft magnetic thin film, Fe-Co-
Examples include magnetic alloy thin films having a high saturation magnetic flux density (8 kG or more) and excellent soft magnetic properties, such as Si-based soft magnetic thin films and Fe-Al-Si-based soft magnetic thin films.

As the Fe-Ga-Si-based soft magnetic thin film, the composition, Fe _a Ga _b Si _c (where, a, b, c are representative. Each composition ratio as atomic%) in the case of the, the composition range , 68 ≦ a + b ≦ 84 1 ≦ b ≦ 23 9 ≦ c ≦ 31 a + b + c = 100.

In the Fe-Ga-Si based soft magnetic thin film, part of Fe may be replaced with Co. In this case, not only the saturation magnetic flux density but also the corrosion resistance and wear resistance are improved with the increase of Co. However, if the Co substitution amount is too large, not only the saturation magnetic flux density is significantly deteriorated but also the soft magnetic characteristics are deteriorated. , For Fe
The Co substitution amount is preferably suppressed to 0 to 15 atom%.

That is, when the composition of the Fe-Ga-Si-based soft magnetic thin film is Fe _d Co _e Ga _f Si _g (where d, e, f, and g are the composition ratios expressed as atomic%), The composition range thereof satisfies the relationship of 68≤d + e≤840 0 <e≤15 1≤f≤35 1≤g≤35 d + e + f + g = 100.

In order to further improve the corrosion resistance and wear resistance of the Fe-Ga-Si-based soft magnetic thin film, Fe, Ga, Co (a part of Fe is Co
(Including those substituted with Ti), Ti with an alloy with a basic composition of Si,
At least one of Cr, Mn, Zr, Nb, Mo, Ta, W, Ru, Os, Rh, Ir, Re, Ni, Pd, Pt, Hf and V may be added.

That is, the composition of the Fe-Ga-Si-based soft magnetic thin film is represented by Fe _h Co _i Ga _j Si _k M _m (where h, i, j, k, m represent the composition ratio in atomic%, and M represents Ti, Cr, Mn, Zr, Nb, Mo, Ta, W, Ru, Os, Rh, Ir, Re, Ni, P
Represents at least one of d, Pt, Hf, and V. ), The composition range satisfies 68 ≦ h + i ≦ 84 0 ≦ i ≦ 15 1 ≦ j ≦ 23 6 ≦ k ≦ 31 0.05 ≦ m ≦ 15 h + i + j + k + m = 100. A soft magnetic thin film may be used. Here, if the addition amount m of the additional element M is less than 0.05 atom%, sufficient effects on wear resistance and corrosion resistance cannot be obtained, while if the addition amount m exceeds 15 atom%, the soft magnetic properties deteriorate. And decrease in saturation magnetic flux density are not preferable. However, since the addition amount m and the reduction ratio of the saturation magnetic flux density are different for each addition element M, the addition amount m is appropriately set within the above range for each addition element.

The composition range of the above Fe-Al-Ge soft magnetic thin film is Fe _u Al _v Ge _w (where u, v, and w are compositional ratios in atomic%). Satisfies the relation of 68 ≦ u ≦ 84 1 ≦ v ≦ 31 1 ≦ w ≦ 31 u + v + w = 100.

When the composition of the Fe-Ga-Ge based soft magnetic thin film is Fe _o Ga _p Ge _q (where o, p, and q are compositional ratios in atomic%), the composition range is Satisfies the relation of 64 ≦ o ≦ 84 1 ≦ p ≦ 35 9 ≦ q ≦ 35 o + p + q = 100.

The composition range of the above Fe-Si-Ge soft magnetic thin film is Fe _r Si _s Ge _t (where r, s, and t are compositional ratios expressed as atomic%). Satisfies 80 ≦ r ≦ 90 1 ≦ s ≦ 199 9 ≦ t ≦ 19 r + s + t = 100.

When the composition of the Fe-Co-Si soft magnetic thin film is Fe _x Co _y Si _z (where x, y, and z are the composition ratios in atomic%), the composition range is Satisfies 9 ≦ y ≦ 15 19 ≦ z ≦ 23 x + y + z = 100.

In addition, in these Fe-Al-Ge soft magnetic thin films, Fe-Ga-Ge soft magnetic thin films, Fe-Si-Ge soft magnetic thin films, and Fe-Co-Si soft magnetic thin films, saturation magnetic flux density and corrosion resistance ， In order to improve wear resistance, soft magnetic thin film in which part of Fe is replaced by Co may be used. Furthermore, in order to further improve the corrosion resistance and wear resistance of each soft magnetic thin film. In addition, Ti, Cr, Mn, Zr, Nb, Mo, Ta, W, Ru, Os, Rh, Ir, R
A soft magnetic thin film formed by adding at least one of e, Ni, Pd, Pt, Hf and V may be used. In this case, the substitution amount of Co and the addition amount of the additional element are set to be substantially equal to the substitution amount and the addition amount in the Fe-Ga-Si based soft magnetic thin film.

As the Fe-Al-Si soft magnetic thin film, those having a composition conventionally used as a core material of a composite magnetic head of this type are used, and particularly, Co is added to the Fe-Al-Si soft magnetic thin film. The soft magnetic thin film thus obtained has improved saturation magnetic flux density, corrosion resistance, and wear resistance, and is suitable as the core material. In this case, the composition of the soft magnetic thin film is set within the range of Co 5 to 15 atom%, Al 8 to 13 atom%, Si 10 to 17 atom%, and the balance Fe.

Further, in order to further improve the corrosion resistance and wear resistance of the Fe-Al-Si-based soft magnetic thin film, Fe, Al, Co (a part of Fe is
The above-described additional element M may be added to the same extent to alloys having a basic composition of Si (including those substituted with Co) and Si.

Here, as a method for forming these magnetic alloy thin films (3) and (13), various conventionally known methods are conceivable. Among them, the vacuum thin film forming technique is preferable.

Examples of the technique of this vacuum thin film forming technique include sputtering, ion plating method, vacuum deposition method, cluster ion beam method and the like. In particular, sputtering may be performed in an inert gas (Ar gas or the like) atmosphere containing oxygen gas or nitrogen gas to further improve the corrosion resistance and the like of the obtained soft magnetic thin film.

In addition, as a method of adjusting the composition of each of the above-mentioned component elements, i) each component element is weighed so as to have a predetermined ratio, and these are melted in advance in, for example, a high-frequency melting furnace to form an alloy ingot. , A method of using this alloy ingot as an evaporation source, ii) a method of preparing evaporation sources of individual elements of each component, and controlling the composition by the number of these evaporation sources, iii) preparation of evaporation sources of individual elements of each component Then, the output (applied voltage) applied to these evaporation sources is controlled to control the evaporation speed to control the composition, iv) a method of implanting another element while evaporating the alloy as the evaporation source, and the like.

The soft magnetic thin film formed by the above-mentioned vacuum thin film forming technique has a slightly higher coercive force in the state as it is, and good soft magnetic characteristics cannot be obtained. It is preferable to remove and improve the soft magnetic properties.

On the other hand, as the oxide magnetic material occupying most of the magnetic core halves (I) and (II), for example, Mn-Zn ferrite or Ni-Zn ferrite is used. Further, the oxide magnetic material may be either a single crystal oxide magnetic material or a polycrystalline oxide magnetic material. Further, the single crystal oxide magnetic material and the polycrystalline oxide magnetic material are so-called hot It may be a joined body integrated by a pressure treatment method or the like.

The present inventors have proposed, as the magnetic alloy thin films (3) and (13), Fe—Al—Si soft magnetic thin films (Fe83.5 atomic%, Al5.5 atomic%, Si11 atomic) with a saturation magnetic flux density Bs of 10 kG. %) And the saturation magnetic flux density Bs is 12kG, 13kG, 15kG Ru-added Fe-Ga-Si-based soft magnetic thin films are prepared, and the film thickness d of these soft magnetic thin films is changed.
A composite magnetic head for overwriting shown in FIGS. 1A and 1B was produced. Then, with respect to each of these composite magnetic heads, various characteristics of the heads were examined. As a result, the relationship between the film thickness d and the saturation magnetic flux density Bs is within the region shown by the shaded area in FIG. 2 (including the boundary line), that is, in FIG. When the relation between (kG) and film thickness d (μm) is expressed in Cartesian coordinate system as (Bs, d), (5.5,10), (7,10), (16,1), (10,1)
It was confirmed that the overwriting composite magnetic head using the magnetic alloy thin film existing in the region surrounded by the four points exhibits good head characteristics.

In the composite magnetic head for overwriting of the present invention, it is necessary that the film thickness d of the magnetic alloy thin film and the saturation magnetic flux density Bs satisfy the above-mentioned relationship, and within the region shown by diagonal lines in FIG. If a magnetic alloy thin film having a film thickness d and a saturation magnetic flux density Bs is used for), the magnetic flux in the long wavelength region (about 130 kHz) is easily saturated, and as a result, the noise due to the unerased signal is drastically reduced, and the recording / reproducing characteristics It is an excellent composite magnetic head.

For example, when the film thickness d of the magnetic alloy thin films (3) and (13) is less than 1 μm, the wear amount per unit contact area of the magnetic alloy thin films (3) and (13) is the magnetic core portions (1), (13). 11)
Due to its large size, the magnetic gap g
A step is generated in the vicinity. This step deteriorates the close contact state between the head and the medium during recording and causes a spacing between the magnetic gap g and the medium, and this step acts as a so-called pseudo gap, which causes a ripple in the reproduction output frequency characteristic. Therefore, the reproduction characteristic is deteriorated.

Further, if the film thickness d is made extremely small, the merit of disposing the magnetic alloy thin films (3) and (13) is weakened, a large recording magnetic field cannot be obtained, and the recording characteristics for the high coercive force magnetic recording medium deteriorate.

On the other hand, if the film thickness d exceeds 10 μm, it takes a long time to form the magnetic alloy thin films (3) and (13), and the merits in terms of productivity, mass productivity and manufacturing cost are diminished. Moreover,
Even if the film thickness d exceeds 10 μm, various characteristics such as recording characteristics cannot be expected to be improved.

In addition, when (Bs, d) in FIG. 2, (7,
A composite for overwriting using a magnetic alloy thin film having a saturation magnetic flux density Bs and a film thickness d in a region (not including the boundary line) above the line connecting the point 10) and the point (16,1) In the magnetic head, since the signal is strongly magnetized in the medium, when a new signal is overwritten on this signal, it cannot be magnetized sufficiently.

On the contrary, when (Bs, d) in Fig. 2, (5.5,1
Overwriting composite using a magnetic alloy thin film having a saturation magnetic flux density Bs and a film thickness d in a region (not including the boundary line) below the line connecting the point (0) and the point (10,1) In the magnetic head, a sufficiently large recording magnetic field corresponding to the high coercive force of a metal tape or the like cannot be obtained, and it becomes impossible to record a signal on this medium.

The present inventors applied the above Fe to the magnetic alloy thin films (3) and (13).
Using a -Ga-Si soft magnetic thin film (Bs = 10 kG), this film thickness d
A composite magnetic head for overwriting was prepared by changing the above, and the relationship between the film thickness d and the recording output at each recording wavelength (4.7 MHz, 1.5 MHz, 130 kHz) was investigated. Here, the evaluation of the recording output is
The magnetic alloy thin film is arranged at an angle of about 45 ° with respect to the magnetic gap surface, and the material of the thin film, the track width, the gap length,
Depth and the like are expressed as the recording output ratio of the head of this embodiment and the same composite magnetic head (comparative example).

As is clear from FIG. 3, it was found that as the film thickness d of the magnetic alloy thin film was reduced, the recording output ratio was also deteriorated, and in particular, magnetic saturation was remarkable on the long wavelength side (low frequency band). Here, in the overwriting method to which the present invention is applied, if the recording output in the long wavelength band (about 130 kHz) is lower by about -4 to -6 dB than the composite magnetic head of the comparative example,
It has been confirmed that good overwrite characteristics can be obtained.
Therefore, the shaded area in Fig. 2 (including the boundary line)
It was confirmed that the use of the magnetic alloy thin film described in (1) provides a composite magnetic head having excellent recording ability for a high coercive force magnetic recording medium and having no noise due to an unerased signal.

〔The invention's effect〕

As is clear from the above description, the overwrite composite magnetic head of the present invention satisfies the relationship between the film thickness and the saturation magnetic flux density such that a sufficient recording magnetic field can be generated for the high coercive force magnetic recording medium. Since a magnetic alloy thin film that is used as the main core material is used, it exhibits excellent recording characteristics for metal tapes and the like that are compatible with higher density and higher quality. Further, in the above magnetic alloy thin film, since the recording output is reduced to some extent in the long wavelength region, when the overwriting method is applied, the unerased portion of the previous signal is eliminated, resulting in excellent reproduction characteristics without noise. To be

At the same time, since the thickness of the magnetic alloy thin film is set to be extremely thin at 1 to 10 μm, productivity and mass productivity can be secured.

Furthermore, since the composite magnetic head for overwriting of the present invention has a simple structure similar to that of a conventional ferrite head, it is advantageous in terms of productivity and manufacturing yield.

Therefore, according to the present invention, excellent recording characteristics are exhibited in a wide frequency band even for a high coercive force magnetic recording medium which is prevalent in the field of R-DAT and the like, and high recording density and high quality are achieved. It is possible to provide a composite magnetic head for overwriting suitable for use at low cost.

[Brief description of drawings]

FIG. 1 (A) is a schematic perspective view showing an embodiment of a composite magnetic head for overwriting to which the present invention is applied, and FIG.
FIG. 4 is an enlarged plan view of an essential part showing a sliding surface of a magnetic recording medium of the overwriting composite magnetic head shown in FIG. FIG. 2 is a characteristic diagram showing a setting region of the film thickness and the saturation magnetic flux density of the magnetic alloy thin film. FIG. 3 is a characteristic diagram showing the film thickness dependence of the recording output ratio when the recording frequency is changed. I, II …… Magnetic core half 1,11 …… Magnetic core (oxide magnetic material) 3,13 …… Magnetic alloy thin film

Claims (1)

(57) [Claims] 1. A pair of magnetic core halves composed of an oxide magnetic material and a magnetic alloy thin film are butted against each other, and a magnetic gap is formed by the magnetic alloy thin films, and the oxide is formed in the vicinity of the magnetic gap. A composite magnetic head in which a boundary surface between a magnetic material and a magnetic alloy thin film is substantially parallel to a magnetic gap surface, and a saturation magnetic flux density Bs (kG) and a film thickness d of the magnetic alloy thin film.
The area surrounded by four points (5.5,10), (7,10), (16,1), and (10,1) when the relationship of (μm) is expressed in Cartesian coordinate system as (Bs, d). A composite magnetic head for overwriting characterized by being set inside