JPH0465444B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a thin film magnetic head suitable for video tape recorders and the like. [Prior Art] In recent years, metal tapes have become popular as magnetic tapes used in video tape recorders, and with this, thin film magnetic heads whose core material is a sendust film with a high saturation magnetic flux density have attracted attention as a magnetic head suitable for such magnetic tapes. It has been confirmed that this head has superior performance compared to conventional ferrite heads. Such a thin film magnetic head is basically constructed by sandwiching a Sendust film between two non-magnetic substrates, but the width of the recording track to be formed on the magnetic tape is relatively wide, and the Sendust film is sandwiched between two non-magnetic substrates. Since the thickness of the film determines the track width, the thickness of the sendust film must be relatively large. However, the resistance value of the sendust film is very small, and when the film thickness is increased,
The eddy current loss at high frequencies becomes significantly large, and the regeneration efficiency at high frequencies decreases. Therefore, in order to eliminate such defects, a plurality of sendust films and electrically insulating nonmagnetic insulating films are alternately laminated between the nonmagnetic substrates, and a thin film magnetic film is created to form a multilayer structure and obtain a predetermined track width. It constitutes the core material of the head, and increases the electrical resistance of the core material to significantly reduce eddy current loss at high frequencies. By the way, in a thin film magnetic head made of the core material of such a Sendust multilayer film, it has been proposed that the thickness of the Sendust film be approximately 6 μm, and the thickness of the nonmagnetic insulating film between the Sendust films be 0.5 μm. (Japanese Patent Application Laid-Open No. 49-127195). This, as mentioned above,
By setting the respective film thicknesses of the Sendust film and the non-magnetic insulating film, the saturation magnetic flux density for the Sendust film
It is said that this is due to the fact that B _s /H _c between B _s and coercive force H _c becomes maximum. However, in the conventional thin film magnetic head described above, when a SiO ₂ film is used as the nonmagnetic insulating film, the thermal expansion coefficient α is different between the sendust film and the SiO ₂ film. If the film thickness is set to 0.5 μm as described above, stress will be applied to the sendust film, resulting in deterioration of the magnetic properties. In other words, even if the thickness of the Sendust film and non-magnetic insulating film is set so that the B _s /H _c of the Sendust film is maximized, the effects of the type of non-magnetic insulating film, coefficient of thermal expansion α, heat treatment, etc. Therefore, it has not been possible to obtain a thin film magnetic head with good magnetic properties. [Object of the invention] The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
It is an object of the present invention to provide a thin film magnetic head that has good magnetic properties over the entire target frequency band regardless of the nonmagnetic insulating film provided between the sendust films. [Summary of the Invention] In order to achieve this object, the present invention sets the thickness of the sendust film forming the core material to 1 to 10 μm, and also sets the thickness of the nonmagnetic insulating film to 0.03 μm.
The feature is that the thickness is less than 0.1 μm. When creating a thin-film magnetic head using a sendust film with a track width of several tens of micrometers, we first considered that since sendust has a significantly lower resistivity than ferrite, the initial permeability deteriorates at high frequencies due to eddy current loss. need to be considered. This is the Skin Debs formula, i.e. However, ρ: Specific resistance of Sendust (≒100μΩ−
cm) ω: Frequency μ _p : Magnetic permeability in vacuum μ _c : Magnetic permeability of sendust (core) t _s : Can be estimated by substituting the specific resistance ρ and frequency ω of sendust into the film thickness. Furthermore, when making a thin film magnetic head using the core material of Sendust, it is necessary to take into account that the magnetic properties deteriorate due to stress, that is, magnetostriction occurs, since it goes through processes such as heat treatment. Considering these points, we selected a composition of sendust that would make the magnetostriction zero, formed a sendust film by sputtering, and investigated its characteristics.We found that the frequency characteristics deteriorated due to skin depth. It was found that the film thickness was approximately 13 μm or more. Then, when we stacked two 15 μm thick Sendust films with a SiO ₂ film in between and measured their magnetic properties, we found that the initial magnetic permeability was particularly low compared to the magnetic properties of a single layer of 15 μm thick Sendust films. It was approximately 1/2 or less across the frequency band (~10MHz). Next, we created a single-layer Sendust film with a thickness of about 8 μm and examined its magnetic properties, and found that compared to a single-layer Sendust film with a thickness of 13 μm,
The initial permeability improved in parallel over the entire frequency band. On the other hand, when the film thickness t _s is calculated from the above skin depth formula for the core's initial magnetic permeability μ _c 1000, 2000 when the frequencies are 100 KHz and 4 MHz, it is as follows.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a front view showing an embodiment of the thin film magnetic head according to the present invention, in which 1 and 1' are nonmagnetic substrates,
2, 2', 2'' are sendust films, 3, 3' are non-magnetic insulating films, 4 is an adhesive, 5 is a gear spacer,
6 and 6' are core halves. FIG. 2 shows the magnetic tape sliding surface of the thin film magnetic head. In the figure, core halves 6,
6' is a non-magnetic insulating film 3, between the non-magnetic substrates 1, 1'.
The sendust films 2, 2', 2'' are laminated through the core halves 6, 6', and the sendust film 2'' is bonded to the non-magnetic insulating film 1' with the adhesive 4. ' are integrated via a gear spacer 5 to form a thin film magnetic head. The nonmagnetic substrates 1 and 1' are made of, for example, Mn-Ni oxide with a coefficient of thermal expansion α of about 140×10 ^-7 /deg, and the nonmagnetic insulating films 3 and 3' are made of, for example, a SiO ₂ film. For example, low melting point lead glass is used as the adhesive. The total thickness from the sendust film 2 to the sendust film 2'' becomes the track width of the thin film magnetic head, and the gap spacer 5 forms a head gap having a predetermined azimuth angle with respect to the track width.Sendust films 2, 2' , 2″ and the nonmagnetic insulating film 3,
The film thickness with 3' is set so that the magnetic properties of the thin film magnetic head are good in the entire frequency band,
In particular, the thickness of the non-magnetic insulating films 3 and 3' is set taking into account the prevention of film peeling between the sendust films 2, 2' and 2''. The thickness will be explained taking into account the experimental results shown in Figures 1A and B. First, the manufacturing of the thin film magnetic head shown in Figure 2 will be explained. Figures 3 A to G show the manufacturing of the thin film magnetic head shown in Figure 2. In the process diagram showing a specific example of the method, 7 is a core material, and parts corresponding to those in Figure 2 are given the same reference numerals.First, the thermal expansion coefficient α is approximately ¹⁴⁰ deg Mn
-Nonmagnetic substrates 1 and 1' made of Ni oxide were prepared (Fig. 3A), and sendust was deposited on the nonmagnetic substrate 1 at a rate of 3 μm/hour to a thickness of about 8 μm using a DC 4-pole sputtering device. Sendust film 2 with a film thickness of
Then, using an RF sputtering device, SiO ₂ is sputtered to form a SiO ₂ nonmagnetic insulating film 3.
is formed to a thickness of about 700 Å (Figure 3B). Using the same method, a sendust film 2' with a thickness of about 8 μm, a SiO ₂ film 3' with a thickness of about 700 Å, and a sendust film 2'' with a thickness of about 8 μm are successively formed (FIG. 3C). On top of the sendust film 2'', a low melting point lead glass is sputtered using an RF sputtering device at a power of 1 W/cm ² to form an adhesive material 4 made of the low melting point lead glass with a thickness of about 0.25 μm. (3rd
Figure D), similarly, on the other non-magnetic substrate 1',
A similar adhesive material 4 is formed to a thickness of about 0.25 μm.
Next, the substrate obtained in this way is attached to an adhesive 4.
are brought into contact with each other and heated under weight to form a sandwich-like core body 7 (FIG. 3F). After forming the sendust films 2, 2, 2'' by sputtering, heat treatment and annealing are performed to obtain the desired magnetic properties, and then the adhesive 4 is sputtered to bond the nonmagnetic substrate 1' and the sendust film 2''. The core body 7 may be formed by adhesion, or the adhesive material 4 may be sputtered on only one of the nonmagnetic substrate 1' and the sendust film 2'' to form the core body 7. is cut at a predetermined azimuth angle to form core halves 6, 6', and the cut surfaces that will become the head gap surfaces are polished and lapped to form gap abutting surfaces.Then, the respective gap abutting surfaces are formed. Then, sputter a non-magnetic gear spacer material 5 made of, for example, SiO ₂ onto the abutting surfaces of each gear (FIG. 3G), and align the core halves 6, 6' so that the gear spacer materials 5 are in contact with each other. The thin film magnetic head shown in Fig. 2 is obtained by butting and bonding with weighted heating.The thin film magnetic head is obtained in this way, and by the same manufacturing method, as shown in Fig. 1, When core bodies with different film thicknesses per layer of sendust film were created and thin film magnetic heads were created from each core body and the output (self-recording/reproducing output) of each head was measured, the results were as shown in Figure 4. In Figure 4, the horizontal axis shows the initial permeability per layer of Sendust film at 4MHz, and the vertical axis shows the initial magnetic permeability at 4MHz.
As is clear from Fig. 4, the head output rapidly increases from around 800 to 1000, which is the same as the initial permeability in Fig. 1A. sendust film 1
This corresponds to the relationship with the film thickness per layer. Although Figure 4 shows the head output at 4MHz, the head output at 1MHz also showed exactly the same tendency. The output measurement conditions at this time were that the relative speed between the thin film magnetic head and the magnetic tape was 4.1 m/sec, the track width was 24 μm, and the inductance was 2 μH. In this way, when the initial magnetic permeability is around 800 or more, a rapid increase in head output is observed. Therefore, from Figure 1A, the film thickness per layer of sendust film should be made thinner than 8 to 10 μm. As a result, a large head output can be obtained. Incidentally, since the saturation magnetic flux density B _s and the coercive force H _c are constant with respect to the film thickness of one Sendust film (FIG. 1B), there is no need to take these into account. Next, by the manufacturing method shown in FIGS. 3A to 3G, six layers of Sendust films with a film thickness of 4 μm are laminated.
A plurality of core bodies having nonmagnetic insulating films of SiO ₂ having different thicknesses in the range of 0.01 μm to 0.52 μm were prepared, and a thin film magnetic head was created from each core body. For each thin-film magnetic head, the head output at 4 MHz and the defective rate of Sendust film peeling were investigated. As a result, as shown in FIG. 5, as the thickness of the nonmagnetic insulating film increases, the head output α decreases and the defective rate b due to film peeling also increases. In particular, it was found that the head output decreased when the thickness of the nonmagnetic insulating film exceeded 1000 Å. This film peeling failure rate b is influenced by the difference in thermal expansion coefficient α between the Sendust film and the nonmagnetic insulating film, and the nonmagnetic insulating film is SiO ₂
As mentioned above, in the case of alumina, which has a larger coefficient of thermal expansion α than SiO ₂ , a thicker film tends to result in a decrease in output and a higher rate of defective films due to film peeling than in the case of SiO ₂ . In addition, in the case of a nonmagnetic insulating film made of SiO ₂ , a decrease in head output was observed when the film thickness approached 300 Å, and the output decreased by approximately 0.5 dB when the film thickness approached approximately 100 Å. Furthermore, in an experiment with the thickness of the non-magnetic insulating film set to 100 Å or less, it was found that in the case of a non-magnetic insulating film with a thickness of about 50 Å, a Sendust multilayer film with a film thickness of 4 μm per layer does not necessarily have good magnetic properties. It was not something that could be obtained. This is because the effect of the non-magnetic insulating film has weakened due to pinholes in SiO ₂ or because the insulation is no longer necessarily good. Therefore, from the above, the thickness of the non-magnetic insulating film of the thin-film magnetic head shown in Fig. 2 is 0.03 μm or more.
Set within the range of less than 0.1 μm. Next, another specific example of the method for manufacturing a thin film magnetic head according to the present invention will be described. A sendust film with a thickness of 5 μm was formed on a nonmagnetic substrate of Mn-Ni oxide using a DC 4-pole sputtering device, and then a nonmagnetic insulating film with a thickness of 1000 Å was formed by sputtering alumina using an RF sputtering device. Formed. This process was repeated 5 times to sequentially form 5 layers of Sendust films each having a thickness of 5 μm with the nonmagnetic insulating film interposed therebetween. Next, this Sendust multilayer film substrate was placed in a vacuum
Annealing is performed for 30 minutes at 600°C in a furnace at 10 ^-2 to 10 ^-3 Torr, and the top of the sendust film is then gently lapped and cleaned, and the low melting point glass containing about 70 to 80% lead is coated with the sendust film. and sputtered onto the other Mn--Ni oxide nonmagnetic substrate to a thickness of 0.25 μm. These two substrates are butted together with their low melting point glass films brought into contact with each other, heated under weight under the same conditions as the annealing conditions, and the sendust films are laminated in a sandwich pattern to form a core body. Next, this core body is cut at a predetermined azimuth angle to obtain two core halves. The cut surfaces of these core halves are mirror-finished to form head gap surfaces, and lead-based low melting point glass is sputtered onto these head gap surfaces using an RF sputtering device.
An adhesive material with a thickness of approximately 0.15 μm is formed. and,
The two core halves are butted together so that their respective adhesives are in contact with each other, and bonding is performed in a vacuum furnace at 10 ^-2 to 10 ^-3 Torr at a temperature lower than that during lamination, followed by a predetermined process to form a thin film magnetic material. A head is created. The thin film magnetic head thus obtained has an effective gap length of about 0.25 to 0.3 μm,
This sufficiently satisfies short wavelength recording. Note that in the above embodiments and manufacturing method, the case where the Sendust film is laminated only on one non-magnetic substrate and the other non-magnetic substrate is bonded to this is explained, but the Sendust film is laminated on both non-magnetic substrates respectively. It is also possible to laminate them by stacking them and butting them together, and as a non-magnetic insulating film
SiO ₂ .Not limited to alumina. [Effects of the Invention] As explained above, according to the present invention, the thickness of each layer of the sendust film to be stacked is 1 to 10 μm.
The thickness of the nonmagnetic insulating film between the sendust films is
Since it is 0.03 μm or more and less than 0.1 μm,
without changing the saturation magnetic flux density and coercive force.
The initial magnetic permeability increases significantly and the magnetic properties are improved,
The head output is significantly increased and there is almost no variation in performance.Furthermore, it is possible to reduce film peeling defects without deteriorating performance, and the manufacturing yield is greatly improved, which is not possible with the above conventional technology. A thin film magnetic head with excellent functionality can be provided.

[Brief explanation of the drawing]

FIGS. 1A and 1B are characteristic diagrams showing the experimental results of the magnetic properties of stacked Sendust films, FIG. 2 is a front view showing an embodiment of a thin film magnetic head according to the present invention, and FIGS. Figure 2 is a process diagram showing a specific example of the manufacturing method for the thin film magnetic head, Figure 4 is a characteristic diagram showing the measurement results of the reproduction output versus the initial magnetic permeability of the thin film magnetic head in Figure 2, and Figure 5 is a diagram showing the measurement results of the reproduction output with respect to the initial magnetic permeability of the thin film magnetic head in Figure 2. FIG. 3 is a characteristic diagram showing measurement results of reproduction output with respect to the film thickness of the nonmagnetic insulating film of the thin-film magnetic head shown in the figure. 1, 1'... Nonmagnetic substrate, 2, 2', 2''... Sendust film, 3, 3'... Nonmagnetic insulating film.

Claims (1)

[Claims] 1. A thin film magnetic head comprising two core halves each formed by laminating a plurality of sendust films between two nonmagnetic substrates with only a nonmagnetic insulating film interposed therebetween, and integrated through a gear spacer, the core The thickness of the sendust film of each half is 1 to 10 μm, and the thickness of the nonmagnetic insulating film of each of the core halves is 0.03 μm.
A thin film magnetic head characterized in that the thickness is greater than or equal to 0.1 μm.