JPH0422282B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a magnetic head for a magnetic recording device (hereinafter referred to as a magnetic head), and more specifically, the present invention relates to a magnetic head for a magnetic recording device (hereinafter referred to as a magnetic head), and more specifically, two high permeability magnetic bodies are connected to each other via an operating gap on a surface facing a magnetic recording medium. The present invention relates to a magnetic head having opposing magnetic cores, at least one of which is made of single crystal ferrite. [Prior Art] There is an extremely strong demand today for advancement of magnetic recording technology, especially for increasing the density of magnetic recording. In order to meet this demand, it is necessary to increase the coercive force, increase the magnetic flux density, and lower the noise of magnetic recording media.
Significant improvements in the recording characteristics and reproduction sensitivity of magnetic heads have become a major challenge. The present invention was achieved as a result of extensive research to solve the above problems, and provides a magnetic head with significantly superior recording and reproducing characteristics compared to conventional magnetic heads of the same type. For example, as shown in FIG. 1, the magnetic heads that are widely used at present include blocks 11 and 11' made of high magnetic permeability magnetic material through an actuating gap 12 so as to form a coil winding window 10. The coils 13, 1 are connected to the magnetic core formed by joining the
It is constructed by wrapping 3'. In particular, it is generally well known that when single crystal ferrite is used as the high permeability magnetic material forming the magnetic core, a magnetic head with excellent high frequency characteristics and excellent wear resistance can be obtained. The above-mentioned single crystal ferrite is usually cubic system Mn-Zn
Ferrite is used, which exhibits magnetic anisotropy in which the <100> or <111> axis is the axis of easy magnetization, depending on its constituent element composition. However, as to how the above-mentioned crystal axis directions should be arranged in the magnetic core of the magnetic head, much remains unexamined, and there is still no firm guiding principle. It goes without saying that the performance of a magnetic head depends on the distribution of magnetic resistance inside the magnetic core. However, it is difficult to obtain detailed information on changes in magnetic properties due to surface processing of ferrite, especially in the vicinity of the working gap, which strongly controls the properties of the magnetic head. It is extremely difficult to predict what kind of magnetoresistance distribution will be achieved by arranging the orientations. Furthermore, even if this is possible to predict, it is difficult to calculate how to arrange the magnetic anisotropy axis in the working gap to obtain the best recording and playback characteristics, especially with today's high-performance computers. Even when using , it is still extremely difficult. This can be said to be the main reason why the desirable arrangement of crystal axes in a magnetic core is extremely unclear. [Problems to be Solved by the Invention] An object of the present invention is to provide a magnetic head with particularly excellent magnetic recording and reproducing characteristics by skillfully utilizing the magnetic anisotropy of ferrite constituting the magnetic core. . [Means for solving the problem] The structure of the present invention to achieve the above object is as follows:
Two single crystals facing each other through an operating gap
A magnetic head comprising Mn-Zn ferrite, a notch narrowing the width of the ferrite near the working gap, and a non-magnetic member filled in the notch, wherein at least one of the ferrite {110 } plane is made almost parallel to the main magnetic path forming plane, and the angle θ between the <100> direction existing in the {110} plane and the forming plane of the working gap is 5° to 40° or 80° to 120°, and the non-magnetic member is made of glass whose shrinkage rate is lower than that of the ferrite when the temperature is lowered from the fixing temperature to room temperature. However, here, θ is assumed to be a vector directed toward the surface facing the recording medium on the working gap forming surface, and the terminal end of the vector is centered on the starting end of the vector and is directed from the gap forming surface toward the inside of the ferrite. When rotating on the road forming surface, the rotation angle swept by the above vector is assumed to be positive. With such a configuration, the glass filled in the notch of the ferrite applies tensile stress to the ferrite when it solidifies. This tensile stress controls the magnetic anisotropy of the ferrite and improves the recording and reproducing characteristics of the magnetic head. The glass filled in the notch near the working gap has a volume sufficient to apply enough stress to particularly control the recording/reproducing characteristics, and since it surrounds the working gap,
The magnetic properties of ferrite near the operating gap, which are important for recording and reproducing characteristics, can be efficiently controlled. Further, the notch that narrows the width of the ferrite near the working gap narrows the gap width and enables high-density recording, and the glass in the notch also has the role of protecting the gap. The single crystal Mn-Zn ferrite is -2×10 ⁴ ~
It has a magnetocrystalline anisotropy constant of 1×10 ⁴ erg/cc, more preferably −1.5×10 ⁴ to 8×
It has a magnetocrystalline anisotropy constant of 10 ³ erg/cc. In the magnetic head according to the present invention, the ferrite surface near the working gap (excluding the surface facing the magnetic recording medium and the working gap forming surface) is melted and adhered with glass having a shrinkage rate lower than that of the ferrite. A tensile stress is generated within the ferrite, the magnetic anisotropy of the ferrite is controlled by the presence of this tensile stress, and this controlled magnetic anisotropy is utilized to improve the recording and reproducing characteristics. However, if the magnetocrystalline anisotropy constant of the ferrite is outside the above range, a desired magnetic anisotropy cannot be obtained even in the presence of tensile stress, and the effects of the present invention cannot be expected. Note that in order to induce uniaxial magnetic anisotropy within the ferrite surface by applying tension to the surface, the surface must be parallel to the {110} plane. When compressive stress is applied, uniaxial anisotropy is induced in other planes as well, but when this stress is applied through melted glass, tensile stress acts on the glass, which can lead to glass cracking. In addition, since the ferrite surface to which the glass is melted and adhered is mainly the main magnetic path forming surface, it is difficult to induce uniaxial magnetic anisotropy within the surface by applying tension to the ferrite surface. It is necessary to make the main magnetic path forming plane almost parallel to the {110} plane. In the magnetic head of the present invention, single crystal
The reason why the {110} plane of the Mn-Zn ferrite is made substantially parallel to the main magnetic path forming plane is as described above. In addition, the above-mentioned vicinity of the side surface of the working gap mainly refers to the side surface that is approximately parallel to the main magnetic path forming surface, and is approximately radial from the intersection of the side surface and the line of intersection between the surface facing the magnetic recording medium and the working gap forming surface. d or an area with a radius of approximately 10d. However, d
is the depth of the working gap forming surface and is shown in FIG. By melting and adhering glass to the side surface within this range from the working gap forming surface, the magnetic anisotropy of the ferrite can be controlled so as to sufficiently improve the performance of the magnetic head. Further, the vicinity of the side surface of the operating gap corresponds to the well-known side surface of the magnetic core notch in the magnetic head. The magnetic head according to the present invention has two high permeability magnetic materials facing each other across an operating gap, at least one of which is made of single crystal Mn-Zn.
However, as mentioned above, single-crystal Mn-Zn ferrite is excellent as a magnetic core material, so normally both of the two high permeability magnetic materials are made of single-crystal Mn-Zn ferrite. It is more desirable that the Similarly, in the magnetic head according to the present invention, at least one of the single-crystal Mn-Zn ferrites must satisfy the crystal orientation condition, but two single-crystal Mn-Zn ferrites must satisfy the crystal orientation condition.
It is more preferable if all of the Zn ferrites satisfy such crystal orientation conditions. Glass deposited near the side of the working gap typically fills a cutout in the magnetic core in this area, as is well known. Note that this notch was originally provided for the purpose of reducing the track width. When the angle θ is in the range of 5° to 40° or 80° to 120°, the recording and reproducing characteristics of the magnetic head according to the present invention are superior to those of the conventional magnetic head.
If the angle θ is between 10° and 35° or between 85° and 115°, even better recording and reproducing characteristics can be obtained, and when the angle θ is about 25° or about 100°, good results can also be obtained. If the angle θ is outside the range of 5° to 40° or 80° to 120°, recording and reproducing characteristics equivalent to or worse than those of the conventional method can be obtained. The shrinkage rate of the glass used is single crystal Mn-Zn
If the shrinkage rate of the glass is lower than that of ferrite, better recording and reproducing characteristics than conventional ones can be expected, but this cannot be expected if the shrinkage rate of the glass is equal to or higher than that of the ferrite. Note that if the difference between the shrinkage percentage of the glass and the shrinkage percentage of the ferrite is 1.3×10 ^-6 or more, cracks may occur in the vicinity of the working gap, and a decrease in yield in manufacturing the magnetic head is expected. Therefore, the shrinkage rate of glass is lower than that of ferrite, and the difference between the two is 1.3×
More preferably, it is less than 10 ^-6 . Further, the glass may be of any composition as long as the shrinkage rate is within a predetermined range and other well-known design conditions are satisfied. In view of the above-mentioned state of the prior art, the present invention produced a large number of trial magnetic heads using single-crystal Mn-Zn ferrite of various compositions and having various crystal axis orientations, and examined the recording and reproducing characteristics of the trial magnetic heads and the ferrite in the vicinity of the working gap. It was constructed based on a new discovery by the inventors of the present invention, which was obtained as a result of examining the relationship between By simplifying the distribution of the easy axis of magnetic anisotropy in the vicinity of the working gap, and optimizing the orientation angle of the easy axis of magnetization on both sides of the working gap, the recording and reproducing characteristics can be improved. The aim is to provide an excellent magnetic head. As already mentioned, the performance of the magnetic head is strongly influenced by the magnetic properties in the vicinity of the working gap. For example, in the magnetic heads of recent home video tape recorders, the track width is extremely narrow and mechanical strength is maintained, and in order to reduce the total magnetic resistance of the magnetic core, the core width except near the operating gap is In a magnetic head as shown in FIG. 2, which has a shape that is made as thick as possible, there is a growing tendency for the performance of the magnetic head to be strongly influenced by the magnetic properties in the vicinity of the working gap. Therefore, the characteristics of the magnetic head should vary greatly depending on the direction of the axis of easy magnetization in the vicinity of the working gap, and therefore the orientation of the crystal axis of the single crystal ferrite. In addition, the second
In the figure, 20 is a coil winding window, 21 and 2
1' is a ferrite block, 22 is an operating gap,
23 and 23' are coils, and 24 is filled glass. By the way, although the single crystal Mn-Zn ferrite normally used in magnetic heads has a small average magnetostriction constant, it is expressed by λ ₁₀₀ and λ ₁₁₁ <
Although the magnetostriction coefficients in the 100> direction and the <111> direction are different in sign, they are both on the order of 3 to 10×10 ⁻⁶ . A process-affected layer with a depth of several hundred nanometers to several micrometers is formed on the ferrite surface processed by a normal processing method, that is, a peripheral slicer, a dicer, a wire saw, etc., and as a result, the inside of the ferrite is ,
It is known that tensile stress occurs. However, detailed data on how much stress actually occurs is not available. Further, the surface of the magnetic head facing the recording medium is usually polished with an abrasive tape or lap, and the surface facing the recording medium is not only used in magnetic tape devices but also in magnetic head floating type magnetic disk devices. However, contact with the recording medium cannot be avoided, and the processing effects caused by these cannot be ignored. Therefore, although it depends on the magnitude of the magnetocrystalline anisotropy of the ferrite used, the magnetic anisotropy axis near the operating gap in the operating state of a magnetic head composed of single-crystal Mn-Zn ferrite is usually The true state of the distribution is beyond speculation. In fact, by the above processing method, single crystal Mn-Zn ferrite with wide {110} planes (Fe ₂ O ₃ ; 54 mol%, MnO; 27 mol%, ZnO; 19 mol%, 1.17×10 ^-5 deg ^-1 disk with an expansion coefficient of It was found that the direction of the maximum varies depending on the measurement frequency. In other words, on the low frequency side, the magnetic permeability is maximum in the <110> direction in the {110} plane and minimum in the direction perpendicular to this, that is, in the <100> direction, whereas on the high frequency side, this relationship is Reverse. This means that the above ferrite disk has the above {110}
When viewed in-plane, this indicates that an axis of easy magnetization is induced in the <110> direction within the plane. by the way,
Crystal magnetic anisotropy constant of the material of the above ferrite disk
K ₁ is positive and approximately 2 to 4×10 ³ erg/cc, and if there is no processing effect, the <100> direction perpendicular to the <110> direction should be the axis of easy magnetization. In addition, the ratio of the maximum and minimum magnetic permeability observed in the above ferrite disk shows a value of 2 to 5 in the frequency range of 3 to 5 MHz, and when such a material is used and the processing method described above is used, If a magnetic head as shown in FIG. 2 is manufactured, its recording and reproducing characteristics will naturally change significantly depending on the orientation of the crystal axes in the working gap. Based on such knowledge, a magnetic core as shown in Fig. 3 and Table 1 was prepared using a single crystal ferrite block having the same composition as the above single crystal Mn-Zn ferrite, and a coil was wound around it. The recording and reproducing characteristics of the magnetic head were measured. That is, the main magnetic path forming surfaces 32, 32' of the magnetic core having the specifications shown in Table 1 are {110} planes,
The recording and reproducing characteristics of magnetic heads using magnetic cores in which the angle θ between the <100> direction included in the main magnetic path forming plane and the working gap forming surface 33 was varied were compared and evaluated.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. Based on the above basic idea, a magnetic head that is the same as the prototype head described above is made, except that the filler glass 34 has various coefficients of thermal expansion (that is, it has various shrinkage rates), and the main magnetic path is formed. The relationship between the angle formed by the <100> direction existing in the {110} plane parallel to the surfaces 32 and 32' and the working gap forming surface 33, that is, θ in FIG. 3, and the recording and reproducing output of the magnetic head is I asked for it. Thermal expansion coefficient α of the filled glass used (average from room temperature to 350℃)
is 74×10 ^-7 deg ^-1 (−1.3×10 ^-6 ), 80×10 ^-7 deg ^-1
(−1.0×10 ^-6 ), 87×10 ^-7 deg ^-1 (−0.7×10 ^-6 ), 96
×10 ^-7 deg ^-1 (−0.4×10 ^-6 ), 101×10 ^-7 deg ^-1 (−
0.2×10 ^-6 ) and 105×10 ^-7 deg ^-1 (0), and the fixing temperature is about 450°C in both cases. The value in parentheses is the value β obtained by subtracting the shrinkage percentage of the ferrite from the shrinkage percentage of the filled glass. Filled glass 34 is ZnO; 27%, Na ₂ O; 8
%, BaO; 8%, SiO ₂ ; 16%, Al ₂ O ₃ ; 4%,
B ₂ O ₃ ; has a composition of 37% and α is 74×
10 ⁻⁷ deg ⁻¹ , β −1.3×10 ⁻⁶ glass, and ZnO;
29%, Na ₂ O; 3%, K ₂ O; 8%, BaO; 14%,
CaO; 4%, SrO; 4%, _SiO2 ; 9%, _{B2O3 ;}
23%, TiO ₂ ; 5%, Li ₂ O and impurities; 1%
It has the composition, α is 107×10 ^-7 deg ^-1 and β is
0.1×10 ^-6 of glass is mixed in such a proportion that the above α and β values are achieved. Note that the above glass composition is expressed in weight %. The measurement results are shown in FIGS. 5 and 6. Figure 5 shows head output (represents relative output and is in arbitrary units)
This is a graph showing the relationship between and θ (degrees), 51
When using glass with α of 87×10 ^-7 deg ^-1 (β of −0.7×10 ^-6 ), 52 has α of 105×10 ^-7 deg ^-1
This is a curve obtained when glass with (β=0) is used.
FIG. 6 is a graph showing the relationship between head output (representing relative output and in arbitrary units) and α and β when θ is 25°. The recording/reproducing characteristics shown in FIGS. 5 and 6 are for a recording wavelength of 1.4 μm and a frequency of 4 MHz. The selection of α in this example is such that the stress at the interface between the side surface of the working gap portion and the filling glass, which occurs due to the temperature change during welding of the filling glass, becomes tensile toward the ferrite core side. The magnetic anisotropy in the vicinity of the side surface of the working gap was emphasized by further promoting the stress due to the process-affected layer of ferrite in the vicinity of the side surface. θ of the recording and reproducing characteristics of the magnetic head according to this example
The dependence unexpectedly shows a very clear 4-fold symmetry. What is even more important is that the magnetic anisotropy near the working gap is emphasized and θ
By setting the value within a suitable range, it is possible to obtain a magnetic head with extremely good characteristics that could not be obtained with the prior art. The recording/reproducing characteristics shown in Figure 5 are as follows: recording wavelength: 1.4 μm, frequency:
Although this is for 4MHz, such θ dependence is observed in the recording wavelength range of 1 to 20 μm and the frequency range of 0.3 to 20 μm.
This is also observed at 6MHz, and the result is almost the same as that shown in Fig. 5, except that the ratio between the highest and lowest head output values changes somewhat. In addition, the coercive force is 300~
Similar characteristics were obtained when various recording media of 1700 Oe were used. As is clear from FIG. 5, good recording and reproducing characteristics can be obtained when θ is between 5° and 40° or between 80° and 120°, but more preferably when θ is between about 10° and 35° or between 85° and 85°. 115°, and good results can also be obtained when θ is approximately 25° or 100°. In addition,
The magnetic head with θ of around 25° and the magnetic head with θ of around 100°, which give the best results, are symmetrical with respect to the value of Q. That is, in the frequency range of 1 to 6 MHz, Q is θ
The maximum value is reached around 25°, and the minimum value is reached when θ is around 100. Furthermore, among the magnetic heads in this example, α
Some magnetic heads using filled glass with a diameter of 74×10 ^-7 deg ^-1 (β is 1.3×10 ^-6 ) have cracks near the operating gap, and if β is lower than this, the magnetic head manufacturing The yield will decrease. The side surface of the operating gap of the magnetic head in this embodiment (filling glass 34 and ferrite block 3)
The tensile stress σ estimated to occur at the center (at the interface with 6, 36′) is at most 2 to 3 Kg/mm ² , and the magnetostriction constants λ ₁₀₀ and λ ₁₁₁ of the commonly used Mn-Zn ferrite are, respectively, -5×10 ^-6 ~-10×
10 ⁻⁶ and 3×10 ⁻⁶ to 7×10 ⁻⁶ . {110} of single crystal ferrite with such a magnetostriction constant
In order to make the <100> direction in the {110} plane the axis of easy magnetization by applying a tensile stress of 2 to 3 Kg/mm ² to the plane, the magnetocrystalline anisotropy constant K ₁ of the single crystal ferrite is must be within a certain range of values.
Moreover, in principle, it also differs depending on the sign of K ₁ . That is, if K ₁ >0, then K ₁ <
3｜λ ₁₁₁ σ｜, in the range of K ₁ , if K ₁ < 0, then
The above effect is effective in the range of K ₁ where |K ₁ |<3|(λ ₁₀₀ −λ ₁₁₁ )σ|. Using the above values of λ ₁₀₀ , λ ₁₁₁ and σ, the range of K ₁ values in which the above effect is expected is -2×10 ^-4 erg/cc ~
It becomes 1×10 ⁴ erg/cc. The range of values for this _K1 is
This ignores the anisotropy constant K ₂ , which is said to be small in normal ferrite.
Taking into account the presence of K ₂ and safety, a more preferable range of K ₁ is −1.5×10 ⁴ erg/cc to 8×
10 ³ erg/cc. K ₁ of Mn−Zn ferrite is
For example, when Fe ₂ O ₃ has a composition of around 50 mol%,
It shows a tendency to increase as the amount of Fe ₂ O ₃ increases. As is clear from FIG. 6, the effect of the present invention is recognized if the value of β is negative;
More preferable results can be obtained if it is 10 ^-6 or less. Further, as described above, if the value of β is -1.3×10 ^-6 or more, no cracks are observed and good results can be obtained. Therefore, a more preferable range of the value of β is −0.2×10 ⁻⁶ to −1.3×10 ⁻⁶ . The measurement results shown in FIGS. 4, 5, and 6 are Fe ₂ O ₃ ; 54 mol %, MnO; 27 mol %,
ZnO: Single crystal Mn-Zn with a composition of 19 mol%
This was obtained for magnetic heads using ferrite, and single crystals with various compositions shown in Table 2.
When we conducted experiments similar to the above using Mn-Zn ferrite, we found that in the above ranges of θ and β, ferrite of any composition achieved recording and reproducing characteristics that exceeded the highest performance that could be obtained with conventional technology. We were able to obtain a magnetic head with In addition,
Experiments have been conducted with the value of K ₁ between −1.5×10 ⁴ and 2×10 ³ erg/cc, but in the case of −1.5×10 ⁴ erg/cc, 8×
10 ³ erg/cc, so in experiments using ferrite with the composition shown in Table 2, when K ₁ is in the range of -1.5×10 ⁴ to 8×10 ³ erg/cc, It can be said that it was found that good results can be expected.

[Table] The characteristics of the magnetic head described above are obtained for the magnetic head in which the drawing angle φ of the winding window 35 in FIG. However, as shown in Table 3, φ was set at 60° to 30°, and l was set at 50° to 30°.
When experiments were conducted on magnetic heads with various changes in the range of 500 .mu.m, head output characteristics having the same .theta. dependence as described above were obtained.

〔Effect of the invention〕

As described above, according to the present invention, the magnetic anisotropy of the ferrite constituting the magnetic core can be skillfully utilized, and a magnetic head with particularly excellent magnetic recording and reproducing characteristics can be provided.

[Brief explanation of drawings]

1 and 2 are bird's-eye views showing the structure of a magnetic head according to the prior art, FIG. 3 is a front view and a plan view showing a magnetic head according to an embodiment of the present invention, and FIG. 4 shows a shrinkage ratio of ferrite. Figure 5 is a graph showing the relationship between θ and head output for a magnetic head using the same level ^of glass. Figure 6 is a graph showing the relationship between θ and head output.
The figure is a bird's eye view showing a magnetic head according to another embodiment of the present invention. In each figure, 32 and 32' are main magnetic path forming surfaces, 33 is an operating gap forming surface, 34 is a filling glass, 35 is a window for coil winding, 36 and 36' are ferrite blocks, and 51 is a plate with β of -0.7×10 ^-6 , 52 is when β is 0, 70 is the winding window, 72
is an operating gap, and 74 is a filling glass.

Claims (1)

[Scope of Claims] 1. Two single-crystal Mn-Zn ferrites facing each other across a working gap, a notch that narrows the width of the ferrite near the working gap, and a notch that is filled in the notch. A magnetic head having a non-magnetic member, wherein the {110} plane of the at least one ferrite is made substantially parallel to the main magnetic path forming plane, and the <100> direction existing within the {110} plane and the above-mentioned operation The angle θ with the gap forming surface is configured to be 5° to 40° or 80° to 120°, and the shrinkage rate when lowering the temperature of the non-magnetic member from the fixing temperature to room temperature is lower than that of the ferrite. A magnetic head characterized by being constructed of low glass. (However, θ is assumed to be a vector on the working gap forming surface toward the surface facing the recording medium, and the terminal end of the vector is centered on the starting end of the vector, and the main magnetic path is directed from the gap forming surface toward the inside of the ferrite.) (When rotating on the formation surface, the rotation angle swept by the vector is taken as positive.) 2. A patent claim characterized in that the angle θ is configured to be 10° to 35° or 85° to 115°. The magnetic head according to item 1. 3. The magnetic head according to claim 1, wherein the angle θ is about 25° or about 100°. 4. A patent claim characterized in that the value obtained by subtracting the shrinkage percentage of the ferrite from the shrinkage percentage of the glass when the temperature is lowered from the glass fixing temperature to room temperature is -0.2 x 10 ^-6 to -1.3 x 10 ^-6 A magnetic head according to item 1, 2 or 3 of the range. 5. Claims 1 and 2, characterized in that the magnetocrystalline anisotropy constant K ₁ of the single crystal Mn-Zn ferrite is -2×10 ⁴ to 1×10 ⁴ erg/cc.
4. The magnetic head according to item 3, item 3, or item 4. 6. Claims 1 and 2, characterized in that the magnetocrystalline anisotropy constant K ₁ of the single crystal Mn-Zn ferrite is -1.5×10 ⁴ to 8×10 ³ erg/cc.
4. The magnetic head according to item 3, item 3, or item 4.