JPS61243144A - Amorphous alloy for magnetic head - Google Patents

Abstract

PURPOSE:To obtain an amorphous alloy for a magnetic head having higher magnetic permeability than ferrite and showing superior wear resistance and thermal stability by adding atomic percentages of Cr and Ru to an alloy having a specific composition consisting of Fe, Co, Si and B. CONSTITUTION:An amorphous alloy for a magnetic head is manufactured by adding 1-2atom% Cr and 0-4atom% Ru to an alloy having a composition represented by a formula (Fe1-a,Coa)100-b(Sic,Bd)b (where a=0.93-0.95, c+d=1, b=23-27atom%, and c/(c+d)=0.55-0.65].

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a magnetic alloy for a magnetic head, and more particularly to an amorphous alloy for a magnetic head containing Co as a main component.

Current magnetic head materials include crystalline metal materials such as permalloy and sendust, Mu-Zn ferrite, and N1-
Oxide materials such as Zn ferrite are mainly used. Crystalline metal materials have the advantage of having a higher saturation magnetic flux density than ferrite, which is an oxide material.
Since the specific resistance is as low as 100 μΩ·1 or less, the magnetic permeability is significantly reduced in the frequency band (approximately MHz) used in video tape recorders and the like.

On the other hand, ferrite has a large specific resistance and exhibits excellent electromagnetic conversion characteristics even in a high frequency band, and also exhibits high wear resistance, so the Mn-Zn type is mainly used in video heads. However, since ferrite has a small saturation magnetization, recording distortion occurs and there is a lot of noise.

Generally, high-density recording uses a high frequency band. Therefore, the core material for a high-density magnetic head needs to be made thinner or have a larger resistivity ρ in order to prevent deterioration of magnetic permeability due to eddy current loss. Sendust has a large saturation magnetization and a high resistivity compared to permalloy, but it is brittle and cannot be made into a thin plate.

In recent years, excellent magnetic and mechanical properties have been discovered in amorphous alloys that do not have a crystalline structure.

In other words, 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 magnetic crystalline anisotropy. It also has high magnetic permeability and Witzkars hardness of about 1000, which is higher than 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, the use of amorphous alloys as magnetic helad cores for higher density recording requires not only low frequency ranges but also IMH
It is necessary to have high magnetic permeability in a high frequency band above z. To achieve this, it is necessary to satisfy the following requirements: ■ High resistivity, ■ High initial permeability, ■ High wear resistance, ■ High thermal stability, and ■ High corrosion resistance. There is.

We have found that an amorphous alloy that satisfies all of ■■■■■ 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 (1) to (2) in an amorphous alloy of four elements Co, Fe, Si, and B, and further includes Cr, Additionally, Ru was added to further improve wear resistance. That is, the present invention has high initial permeability and high specific resistance, so
The present invention proposes an amorphous alloy that exhibits a magnetic permeability higher than that of ferrite even in the above range, as well as excellent wear resistance and high thermal stability.

(Embodiments of the invention) The main alloy of the present invention is (Fet-a l Cot)+oo-
b(Sic.

B4), and c, d, and b are particularly limited. The alloy of the present invention further contains Cr in the main alloy. O~2.0 at% and Ru are added at O~4.0 at%. In the formula, (+d-1*a) is known to be 0.93 to 0.95 in order to normally make the magnetostriction zero.

The reason for the composition limit in the amorphous alloy for magnetic heads of the present invention is as follows. First, the value of b is a metalloid (St, B
), but if b exceeds 27 atomic %, the saturation magnetic flux density decreases, making it undesirable as a core material for a magnetic head. On the other hand, if the semimetal concentration is 20 atomic % or less, the magnetic permeability decreases and becomes uniform. It becomes difficult to form amorphous alloy. Also, 4
To stably obtain an amorphous thin plate strip with a thickness of 0 μm or more,
It is necessary that the metalloid concentration is 23 atomic % or more.

Regarding Cr, if it is less than 1.0 at %, there is no effect such as corrosion resistance, and if it is more than 2.0 at %, the saturation magnetic flux density decreases. As the amount of Ru added increases, the wear resistance improves, but if it exceeds 4.0 at %, the alloy is difficult to become amorphous and the punching workability deteriorates.

Examples of the main alloy of the present invention will be described in detail below.

(Example of Main Alloy) 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 was 500 to 2000 rpm, and the ejected gas pressure was 0.1 to 1 kg/-.The thin plate produced was approximately 25 m wide, 32 to 49 μm thick, and approximately 20 to 30 m long. It was confirmed by X-ray diffraction that all the thin plates were in an amorphous phase, and the magnetostriction was on the order of 104 and almost zero. Crystallization temperature is determined by DSC (differential scanning calorimeter)
It was decided.

Thickness was measured using a micrometer. Magnetic permeability was measured by the inductance method by winding (20 turns each on the primary and secondary sides) a stack of 10 rings with an outer diameter of 10 fi and an inner diameter of 6 mm, which were punched from thin ribbon. . 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.

As the initial magnetic permeability, 3 m0e and its effective magnetic permeability at IKHz were adopted. T! i! The sum magnetization (σ3) was measured using a VSM in a magnetic field of 10 KOe. Specific resistance was measured by the four-terminal method.

FIG. 1 shows the relationship between specific resistance p and c/c + d.

p is c/c + d in the range of b-23 to 27 atom%
The larger the value, the higher the value.

Figure 2 shows the effects of b and c/c + d on the crystallization temperature.
Various reports have already been made regarding this relationship, which indicates the influence of c, and in extensive experiments, a rapid change in crystal temperature was found when c/c+d was around 0.65.

That is, when c/c + d > 0.65, the crystallization temperature becomes low, which is different from what has already been reported.

Figure 3 shows the amount of wear per 100hr and c/c+
The relationship d is shown. To measure the amount of wear, a normal audio type magnetic head was created from amorphous material that had been quenched with liquid, and after it was attached to a commercially available cassette type deck,
This was carried out using a commercially available normal tube. In addition, the amount of wear is almost constant at c/c + d of 0.2 to 0.4, and gradually decreases when it becomes larger than 0.4, reaching 0.5.
It becomes almost constant at 5 or more.

Good wear resistance is shown when c/c+d is 0.55 or more. In the case of , the value of μl will also differ as b changes, but when c / c + d takes a constant value below 0.4, it increases rapidly between 0.4 and 0.6, and gradually reaches a higher constant value. , that is, when the liquid is quenched, c/c
+ The larger d is, the higher μl is, more preferably c
/ c 10d is preferably 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 measured in b-24 after annealing amorphous alloys (llk17 to 2G) with various c/c + d compositions at various temperatures for 10 minutes and then water quenching. 0 showing the relationship between magnetic permeability and annealing temperature. The effect of annealing temperature on the initial magnetic permeability in amorphous alloys with various compositions is similar, c / c + d
μ irises with a high value of 0.5.0.63! It was confirmed that the composition of 11 was large in the composition of l. Comparing the results, and arranging c/c + d in descending order of μl, they were 0.63°, 0.50, 0.67, and 0.18.

FIG. 6 shows the results of examining the effect of heat treatment on μl in the case of b-25 in the same way as FIG. 5. Comparing the maximum value of μl after various annealing in each sample, and arranging c/c + d in descending order of μl, it is 0.64. 0.6
0.0.50.0.40. 0.6 B, 0.20
becomes.

FIG. 7 shows the case of b-27 with μ
These are the results of investigating the effect of heat treatment on l. Comparing the maximum value of μl after various annealing in each sample and arranging c/c + d in descending order of μl, it is 0.63.
0.50. 0.40. 0.20. It was 0.76.

Figure 8 shows the relationship between the maximum value of μl and c/c + d obtained after annealing for various compositions, b-24°2
In any case of 5.27, μl and C/c+d have the largest value around 0.6.

Also, from the viewpoint of practical materials, it is necessary to take into account variations in properties. For example, when considering heat treatment operations, it is important to obtain high magnetic permeability over a wide heat treatment temperature range.
Increase mass productivity or reliability of materials.

FIG. 9 shows the annealing temperature range (ΔT) in which the value μl>10′ is obtained. The value μ1−10′ is considered to be close to the value required for the Herad core material.

Permalloy and Sendust, which are currently used as core materials for heads, have approximately this value in μl. 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.

Further, the alloys (1) to (24) were left in high humidity air, their surface conditions were observed, and their corrosion resistance was investigated. 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 + dμi (AsQ
) 0.55<c/c+dμl (after heat treatment) 0.5
0<c/c+d<0.65.1Ji(ΔT) 0.
5<c/c+d<0.65 Corrosion resistance c/c
In order to satisfy both the conditions of +d-large, it is necessary that Q, 55<C/C+d<0.65.

Next, the amorphous alloy of the present invention includes Cr and R in the main alloy.
It is added with the u element. 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, and it is 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 alloy to which Cr was added, and as a result of external observation, it was found that the alloy had insufficient corrosion resistance and was not effective, and that if it exceeded 2.0 at%, the saturation magnetic flux density decreased. The addition also had the effect of preventing the alloy from becoming brittle after heat treatment.

Regarding Ru, the greater the amount added, the more the wear resistance can be improved, but if it exceeds 4.0 atomic %, the alloy will be difficult to become amorphous, and the punching workability will also deteriorate. .

Figure 10 shows the main alloy composition samples (patient 1) shown in the table above.
Wear amount (μm ) is expressed in a graph. In the same figure, 19a is the main alloy composition sample (Nl119) with only 1.5 atomic% of Cr added, and 19b is the same sample (Nl119).
N119) with 1.5 at% Cr and 1.0 at% Ru
19C indicates the same sample (Na19) to which 1.5 at. % of Cr and 3.0 at. % of Ru were added. Similarly, 23a is the main alloy composition sample (&23) with 1.5 at% of Cr only added, and 23b is 1.5 at% of Cr and 1.0 at% of Ru.
, 23c contains 1.5 at% Cr and 3.0 at% Ru
It was added. As is clear from the figure, 19a-C
There is no difference in wear resistance between 23a and 23a-c, and as the amount of Ru added increases in any of the main alloy compositions,
The amount of wear is significantly reduced.

Regarding the improvement of characteristics such as specific resistance ρ and μ1, 31. The amount of B is 0.55 < c / c + d
It is sufficient for Cr to satisfy the condition of <0.65.

There is no change even if Ru element is added.

In addition, it is well known that the initial permeability, wear resistance, and specific resistance of amorphous magnetic alloys can be improved by substitution or addition of other elements, but this is not the case in the alloys of the present invention. There is.

[Brief explanation of the drawing]

Figure 1 shows the specific resistance p of the amorphous alloy and St/Si+B(-c
Figure 2 shows the relationship between crystallization temperature and b
A diagram showing the relationship between (temperature of -3i+H)/c+d,
Figure 3 shows the amount of wear per 100 hours and c/c +
Figure 4 shows the relationship between d and the initial magnetic permeability μ of an amorphous alloy.
Figures 5 to 7 are diagrams showing the relationship between m and c/c + d, Figures 5 to 7 are diagrams showing the relationship between b, initial permeability, and annealing temperature, and Figure 8 is µm and c/c. + d, Figure 9 is a diagram showing the relationship between c/c + d and the range of annealing temperature that provides a value of μt>16a, and Figure 10 is a diagram showing the relationship between the amount of Ru added and the amount per hour. FIG. 3 is a diagram showing the relationship with the amount of wear. Fig. 1 "l'sL+B" C/c 10d '/c 10d Fig. 3'/d in c'/c 0d Fig. 5 Fig. 6 m Temperature (0C) Fig. 7 Fig. 8 c /c+d Figure 9 C1c+d Figure 10 When driving lWI (hr)

Claims (1)

[Claims] Composition formula (Fe_1_-_a, Co_a)_1_0_0
____bSi_c, B_d)_b alloy, Cr
1.0 to 2.0 at%, and 0 to 4.0 at% Ru.
An amorphous alloy for magnetic heads characterized by the addition of additives. However, a=0.93-0.95 c+d=1 b=23-27 atomic% c/c+d=0.55-0.65