JPH0463147B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a magnetic alloy for magnetic heads, and more particularly to an amorphous alloy for magnetic heads containing Co as a main component. Current magnetic head materials mainly include crystalline metal materials such as permalloy and sendust, and oxide materials such as Mu--Zn ferrite and Ni--Zn ferrite. Crystalline metal materials have the advantage of having a higher saturation magnetic flux density than ferrite, which is an oxide material, but have a specific resistance of 100μΩ・cm.
Since the magnetic permeability is as low as below, the magnetic permeability significantly decreases in the frequency band (approximately MHz) used in video tape recorders and the like. On the other hand, ferrite has a large resistivity and exhibits excellent electromagnetic conversion characteristics even in a high frequency band, and also exhibits high wear resistance, so Mu-Zn type materials are mainly used in video heads. However, since ferrite has a low saturation magnetization, recording distortion occurs and there is a lot of noise. Generally, high-density recording uses a high frequency band. Therefore, in order to prevent deterioration of magnetic permeability due to eddy current loss, the core material for a high-density magnetic head needs to be made thinner or have a larger specific resistance ρ. Sendust has a large saturation magnetization and a high resistivity compared to permalloy, but it is also brittle.
Cannot be made thinner. In recent years, excellent magnetic and mechanical properties have been discovered in amorphous alloys that do not have a crystalline structure. That is, because amorphous alloys do not have a crystalline structure, their resistivity ρ is several times higher than that of crystalline metal alloys, and their coercive force is small because they do not have magnetocrystalline anisotropy. It also has high magnetic permeability. Furthermore, its Witzkaas hardness is around 1000, which is higher than that of crystalline metals. In addition, the composition that makes magnetostriction zero has basically been elucidated and is being studied as a core material for magnetic heads. However, in order to use an amorphous alloy as a magnetic head core for higher density recording, it is necessary to have high magnetic permeability not only in the low frequency range but also in the high frequency range of 1 MHz or higher. To achieve this, it is necessary to satisfy the following requirements: high specific resistance, high initial permeability, high wear resistance, high thermal stability, and high corrosion resistance. We have found that an amorphous alloy that satisfies both of these can only be obtained in a very narrow composition range. (Objective of the invention) The present invention discloses a composition range that satisfies all of the above in an amorphous alloy of four elements Co, Fe, Si, and B, and furthermore, in order to add corrosion resistance.
Cr and Ru are added to further improve wear resistance, and second phase particles are dispersed in this alloy. In other words, the present invention uses an amorphous alloy that has a high initial magnetic permeability and a high specific resistance, so it exhibits a magnetic permeability higher than that of ferrite even in a band of 1 MHz or more, and also exhibits excellent wear resistance and high thermal stability. This is to be submitted. (Embodiments of the invention) The present invention has a compositional formula (Fe _1-a , Co _a ) _100-b (Si _c ,
B _d ) Limit c, d, and b in the alloy consisting of _b , and add 1.0 to 2.0 atom% of Cr to 100 atom% of the alloy,
The second phase particles are uniformly dispersed three-dimensionally in an alloy to which Ru is added in an amount of 1.0 to 4.0 atomic percent. In the formula, c+d=1, and a is known to be 0.93 to 0.95 in order to normally make the magnetostriction zero. The reasons for limiting the alloy composition are as follows.
First, the value of b indicates the concentration of metalloids (Si, B),
When b exceeds 27 at%, the saturation magnetic flux density decreases,
Not preferred as a core material for magnetic heads. on the other hand,
If the semimetal concentration is less than 20 atomic percent, the magnetic permeability decreases and it becomes difficult to form a uniform amorphous alloy. In addition, in order to stably obtain an amorphous thin plate band with a thickness of 40 μm or more, the semimetal concentration must be 23 atomic % or more. First, the characteristics of the Co-Fe-Si-B alloy will be explained. Amorphous alloy thin plate strips having the compositions shown in the table were prepared according to the single roll liquid quenching method. That is, molten metal is jetted out from a quartz nozzle placed on one rotating steel roll under the pressure of argon gas. The roll rotation speed is 500 to 2000 rpm, and the blowing gas pressure is
It was 0.1-1Kg/ ^cm2 . The width of the created thin plate is approximately
It was 25 mm, 32-49 μm thick, and about 20-30 m long.
It was confirmed by X-ray diffraction that all the produced thin plates were in an amorphous phase, and the magnetostriction was on the order of 10 ^-6 and almost zero. The crystallization temperature was determined by DSC (differential scanning calorimeter). Thickness was measured using a micrometer. Magnetic permeability is determined by winding (20 rings each on the primary and secondary sides) a stack of 10 rings with an outer diameter of 10 mm and an inner diameter of 6 mm, punched from thin ribbon.
) and measured using the inductance method. The magnetic permeability is determined by the state of the ring obtained from the liquid-quenched ribbon, and by annealing the ring (holding at 100°C to 500°C for 10 minutes, then water quenching, holding temperature at 10°C). ℃ interval) at room temperature. The initial magnetic permeability was 3mOe, and its effective magnetic permeability at 1KHz was adopted. Saturation magnetization (σ _s ) was measured using a VSM in a magnetic field of 10 KOe. Specific resistance was measured by the four-terminal method.

[Table] Figure 1 shows the relationship between specific resistance ρ and c/c+d. In the range of b=23 to 27 atomic %, ρ is higher as c/c+d is larger. Figure 2 shows the effects of b and c/c+d on the crystallization temperature.
Show the impact of Various reports have already been made regarding this relationship, but in our experiments, c/c
A rapid change in crystal temperature was found when +d was around 0.65. That is, when c/c+d>0.65, the crystallization temperature becomes low. This fact is different from what has already been reported. Figure 3 shows the amount of wear per 100hr and c/c+
The relationship d shows this. The amount of wear was measured by making an ordinary audio type magnetic head from liquid-quenched amorphous amorphous, attaching it to a commercially available cassette type deck, and using a commercially available normal tape. Also, the amount of wear is c/c+d of 0.2 to 0.4
It is almost constant at , gradually decreases when it becomes larger than 0.4, and becomes almost constant at 0.55 or more. c/
It can be seen that when c+d is 0.55 or more, good wear resistance is exhibited. FIG. 4 shows the relationship between the initial magnetic permeability .mu.i and c/c+d of amorphous amorphous materials having various compositions that have been quenched with liquid. In any case, the value of .mu.i will vary as b changes, but when c/c+d is 0.4 or less, it takes a constant value, increases rapidly between 0.4 and 0.6, and gradually approaches a high constant value. That is, when the liquid is rapidly cooled, the larger c/c+d is, the higher μi is. More preferably, c/c+d is 0.55 or more. It is generally known that the magnetic permeability of amorphous magnetic alloys can be improved by annealing under appropriate conditions. Therefore, we investigated the effect of annealing on magnetic permeability. Figure 5 shows the initial values of amorphous amorphous alloys (No. 17 to 20) with b = 24 and various compositions of c/c + d that were annealed at various temperatures for 10 minutes and then water quenched. The relationship between magnetic permeability and annealing temperature is shown. The effect of annealing temperature on the initial magnetic permeability in amorphous alloys with various compositions is similar, and high μi is obtained when c/c+d is 0.5 and 0.63, and the improvement in initial magnetic permeability by annealing is large for these compositions. This was recognized. Comparing the maximum value of μi after various annealing in each sample, and arranging c/c+d in descending order of μi, 0.63, 0.50, 0.67,
It was 0.18. Figure 6 shows μi as in Figure 5 for the case b = 25.
This is the result of investigating the effect of heat treatment on. Comparing the maximum value of μi after various annealing in each sample, and arranging c/c+d in descending order of μi, 0.64,
0.60, 0.50, 0.40, 0.68, 0.20. FIG. 7 shows the results of examining the effect of heat treatment on μi in the case of b=27, similar to FIG. 5.
Comparing the maximum value of μi after various annealing in each sample, and arranging c/c+d in descending order of μi,
They were 0.63, 0.50, 0.40, 0.20, and 0.76. Figure 8 shows the μi obtained after annealing for various compositions.
The relationship between the maximum value of and c/c+d is shown. b=24,
In both cases 25 and 27, μi is c/c+d
has its largest value around 0.6. In addition, it is necessary to consider variations in properties from the viewpoint of practical materials.For example, when considering heat treatment operations, obtaining high magnetic permeability over a wide heat treatment temperature range increases workability, mass production, and material reliability. . FIG. 9 shows the annealing temperature range (ΔT) in which the value μi>10 ⁴ is obtained. The value μi= ¹⁰⁴ is considered to be close to the value required for head core material. Permalloy is currently used as core material for heads.
Sendust's μi is approximately this value. The larger b is, the larger ΔT is, but the saturation magnetic flux density is smaller. In the case of c+d=24, 25, and 27, the curves are similar, and ΔT takes a large value for each b when c/c+d is around 0.5 to 0.65. Furthermore, alloys (1) to (24) were left in high humidity air, their surface conditions were observed, and their corrosion resistance was investigated. The corrosion resistance was better as c/c+d was larger, regardless of the size of b. A summary of what has been said above is as follows. Specific resistance ρ c/c+d → large Crystallization temperature c/c+d<0.65 Wear resistance 0.55<c/c+d μi (AsQ) 0.55<c/c+d μi (after heat treatment) 0.50<c/c+d<0.65 μi (ΔT) 0.5 <c/c+d<0.65 Corrosion resistance c/c+d→large To satisfy both conditions, it is necessary that 0.55<c/c+d<0.65. Next, Cr and Ru elements were added to the main alloy.
The alloys to which these elements were added were manufactured using the same single-roll liquid quenching method as in the case of the main alloy described above. The reason for adding Cr is to improve corrosion resistance.
It was added in an amount of 1.0 to 2.0 atomic % based on the main alloy. A salt spray test (40°C, 48 hours) was conducted on the added alloy, and as a result of external observation, sufficient corrosion resistance was obtained. Note that if the amount added is less than 1.0 atomic %, there is no effect, and if it exceeds 2.0 atomic %, the saturation magnetic flux density will decrease. Furthermore, the addition of Cr also had the effect of preventing the alloy from becoming brittle after heat treatment. As for Ru, the greater the amount added, the more the wear resistance can be improved, but if it exceeds 4.0 atomic %, the alloy is difficult to become amorphous and the punching workability is also deteriorated. Figure 10 shows the main alloy composition samples (Nos. 19 and 23) shown in the table above, each containing 1.5 at.
and further add 1.0 atom% or 3.0 atom% of Ru.
This is a graph showing the amount of wear (μm) versus running time (hr) for the additives.
In the same figure, 19a is the main alloy composition sample (No.
19) with 1.5 at% Cr added only, 19b
The same sample (No. 19) contains 1.5 atomic% Cr and 1.0 atomic% Ru.
atomic% added, 19c is the same sample (No.19)
1.5 atomic% of Cr and 3.0 atomic% of Ru are shown in the figure. Similarly, 23a is the main alloy composition sample (No. 23) with only 1.5 at% Cr added, 23b is 1.5 at% Cr and 1.0 at% Ru, and 23c is 1.5 at% Cr and Ru. is added by 3.0 atomic%. As is clear from the figure, 19a
-c and 23a-c, there is no difference in wear resistance, and in any of the main alloy compositions, as the amount of Ru added increases, the amount of wear decreases significantly. Regarding the improvement of characteristics such as resistivity ρ and μi, the amount of Si and B in the main alloy is 0.55<c/c+d<0.65.
The fact that it is sufficient to satisfy the following conditions does not change even if Cr and Ru elements are added. Next, the amorphous alloy of the present invention has the above-mentioned main alloy.
Cr and Ru elements are added, and second phase particles are further dispersed in this alloy. To explain the method for manufacturing an amorphous alloy in which second phase particles are uniformly dispersed in an alloy, first, an alloy base material constituting the alloy is heated and melted, and then,
Before the alloy base material solidifies, the second phase particles are sprayed and dispersed onto the alloy base material together with a jetting medium made of an inert gas such as argon gas, and then cooled to contain the second phase particles. After making an ingot and remelting the ingot to such an extent that the second phase particles do not dissolve, the ingot is ultra-rapidly solidified according to the single-roll liquid quenching method to uniformly disperse the second phase particles three-dimensionally in the alloy. be able to. As an example of the present invention, an amorphous alloy having the following composition (a) was prepared in which 2% by volume of A ₂ O ₃ was dispersed in the alloy. As a comparative example, an amorphous alloy having the following composition (b) in which A ₂ O ₃ was not dispersed was prepared. (a) Co _69.5 Fe _4.5 Si _14.5 B _9.0 Cr _1.5 Ru _1.0 +2vol%A ₂
O ₃ (b) Co _69.5 Fe _4.5 Si _14.5 B _9.0 Cr _1.5 Ru _1.0 In (a), scanning electron microscopy shows that A ₂ O ₃ particles are three-dimensionally dispersed in the amorphous alloy. I confirmed it. FIG. 11 shows the change in effective magnetic permeability μe with respect to frequency for the alloys (a) and (b). As is clear from the figure, it can be seen that the decrease in effective magnetic permeability, especially in the high frequency band, is smaller in the alloy (a) in which A ₂ O ₃ is dispersed than in the alloy (b) in which it is not dispersed. In addition, as the second phase particles, in addition to A ₂ O ₃ ,
Oxides such as Fe ₂ O ₃ and SiO ₂ that are incompatible with the alloy,
Carbon or its compounds such as C, WC, TiC, and NbC, metals or alloys such as Ti, Mo, and W, or composites thereof may be used. Regarding the amount of second phase particles added, if the amount is more than 3.0% by volume, it will be difficult to disperse in the amorphous alloy, and if it is less than 0.5% by volume, no significant effect will be seen.

[Brief explanation of the drawing]

Figure 1 shows the resistivity ρ of amorphous alloy and Si/Si+B
(=c/c+d), Figure 2 is a diagram showing the relationship between crystallization temperature and b (=temperature of Si+B) and c/c+d, and Figure 2 is a diagram showing the relationship between crystallization temperature and b (=temperature of Si+B) and c/c+d. /c+d, Figure 4 is a diagram showing the relationship between the initial magnetic permeability μi of an amorphous alloy and c/c+d, and Figures 5 to 7 are the relationship between b and initial permeability, respectively. Figure 8 shows the relationship between μi and annealing temperature.
Figure 9 shows the relationship between c/c+d and μi>
The range of annealing temperature that gives a value of 10 ⁴ and c/c+
Figure 10 is a graph showing the relationship between the amount of Ru added and the amount of wear per hour, and Figure 11 is the effective magnetic permeability of amorphous alloys with and without the addition of A ₂ O ₃ . FIG. 3 is a diagram showing the relationship between μe and frequency.

Claims (1)

[Claims] 1. 1.0 to 2.0 atomic % of Cr to 100 atomic % of an alloy consisting of the compositional formula (Fe _1-a , Co _a ) _100-b (Si _c , B _d ) _b ;
An amorphous alloy for a magnetic head, characterized in that second phase particles are dispersed in an alloy to which Ru is added in an amount of 1.0 to 4.0 atomic percent. However, a = 0.93 to 0.95 c + d = 1 b = 23 to 27 atomic% c/c + d = 0.55 to 0.65 2 The second phase particle is added in a range of 0.5 to 3.0 volume %. The amorphous alloy for magnetic heads according to item 1. 3. The amorphous alloy for a magnetic head according to claim 1 or 2, wherein the second phase particles are composed of A ₂ O ₃ particles.