JPH0339323B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION A. Technical Field The present invention relates to magnetic heads. More specifically, the present invention relates to a contact type magnetic head comprising a core and a dummy block, particularly to improvements in the dummy block. B. Prior Art In a contact type magnetic head, a dummy block is placed along with a core for recording or reproducing on the sliding surface of a magnetic recording medium such as a tape, and when the medium is in contact with another track or the other track of the medium. Considerations have been taken to ensure sliding contact with unused areas, improve media running performance, prevent uneven wear of the magnetic head core and case, and prevent crosstalk between tracks and induced noise. ing. In this case, in a conventional magnetic head having a core made of sendust, permalloy, ferrite, etc., a dummy block made of the same material as the core is used. By the way, amorphous magnetic alloy thin sheets have recently attracted attention as core forming materials for magnetic heads due to their excellent soft magnetic properties, and magnetic heads with cores made of amorphous magnetic alloy thin sheets have been put into practical use. has been moved to. In a magnetic head having a core made of such an amorphous magnetic alloy thin plate, since the amorphous magnetic alloy cannot be obtained as a block body, the dummy block is made of the same material as the core, as in the past. cannot be formed from On the other hand, if a dummy block is formed from conventional magnetic head core materials such as permalloy, high-hardness permalloy, sendust, and ferrite for a core made of an amorphous magnetic alloy thin plate, the magnetic recording medium may be damaged or the frequency characteristics may deteriorate. There are various disadvantages such as deterioration over time and increased output level fluctuations. To be more specific, when permalloy or high-hardness permalloy is used as a dummy block, the hardness of the amorphous magnetic alloy is higher than that of permalloy, which causes uneven wear of the dummy block and poor contact between the medium and the head. With use, frequency characteristics may deteriorate or output level fluctuations may increase. In addition, when using sendust, since the amorphous magnetic alloy for the magnetic head is a Co-based alloy, a local battery is formed between the sendust dummy block and the amorphous magnetic alloy head, especially at high temperatures. Corrosion occurs in the dummy block under humidity, resulting in deterioration of frequency characteristics, causing poor running, increased output fluctuations, and even poor appearance. In addition, sendust is difficult to forge or roll, so it is ground after casting to make a dummy block, but the presence of the cast structure causes damage to the medium, and it is also inefficient in manufacturing. , the cost will be high. Furthermore, when ferrite is used, since it has a higher hardness than an amorphous magnetic alloy, uneven wear occurs, resulting in undesirable phenomena such as deterioration of frequency characteristics, poor media running, and increased output level fluctuations. On the other hand, the present inventors previously reported that 1 to 40 wt.
Contains about % Ni, and Mn, Si, etc. as necessary.
The proposal is to use Fe-Ni alloy as a dummy block. In the Fe--Ni alloy dummy block proposed above, especially when combined with an amorphous core, uneven wear is significantly reduced, and deterioration of frequency characteristics and increase in output fluctuation are significantly reduced. In addition, the dummy block has various characteristics such as high corrosion resistance and less occurrence of poor running of tape, poor appearance, or corrosion during storage. However, the Fe--Ni alloy dummy block proposed in the future requires further improvement in terms of storage stability under high temperature and high humidity, and deterioration of frequency characteristics due to tape running. On the other hand, the present inventors have previously proposed that a dummy block be made of the above-mentioned Fe--Ni alloy to which approximately 15 wt% or less of Cr is added. The alloy dummy block proposed in the future has improved deterioration in frequency characteristics and storage stability under high temperature and high humidity conditions. However, corrosion resistance is not necessarily sufficient, and further improvement in storage stability under high temperature and high humidity is desired.
Improvements are also needed regarding the wear caused by running Fe ₂ O ₃ tape. In addition, further improvements are desired regarding deterioration of frequency characteristics due to uneven wear. Furthermore, if a coated medium made of magnetic powder as an alloy, so-called metal tape, is run for a long period of time, this dummy block may become discolored or have deposits on it, causing a difference in level between it and the core of the magnetic head. Due to the space loss, the high frequency component in particular of the frequency characteristics deteriorates, which is disadvantageous and impairs the performance of the coated metal tape. Purpose of the Invention The present invention has been made in view of the above-mentioned circumstances, and provides a magnetic head, particularly a magnetic head having a core made of an amorphous magnetic alloy thin plate, with less uneven wear and corrosion resistance. A new Fe-Ni product with high resistance to corrosion and wear due to storage under poor conditions and running of γ-Fe ₂ O ₃ tape, and no deterioration of frequency characteristics even when coated metal tape is run for long periods of time. The main object of the present invention is to provide a magnetic head equipped with a dummy block made of an alloy based on the magnetic head. The present inventors have conducted various studies in order to find a new dummy block material that meets these objectives, especially when used in combination with an amorphous magnetic alloy core, and have now accomplished the present invention. It is. That is, the present invention provides a magnetic head comprising a dummy block and a core, in which the dummy block contains 29 to 97.5 wt% Fe and 1 to 40 wt% Ni.
The magnetic head is made of an Fe-Ni alloy containing 1 to 15 wt% of Cr, 0.5 to 4 wt% of Cu, and no Mo. Note that the present inventors previously developed Cr, Cu, and Mo
Therefore, the dummy block of the present invention excludes the addition of Mo. The dummy block of the present invention exhibits the same characteristics as the dummy block proposed earlier. Specific Configuration of the Invention The specific configuration of the present invention will be described in detail below. The dummy block in the magnetic head of the present invention is made of a Fe--Ni alloy having a predetermined composition. In this case, the content of Fe and Ni contained as essential components in the Fe-Ni alloy is 29
~97.5wt%, more preferably 60-86wt%, and 1-40wt%, more preferably 10-30wt%. In addition, the Cr content, which is also an essential component, is 1 to 1.
It is 15 wt%, more preferably 2 to 10 wt%. Furthermore, the Cu content of the fourth essential component is 0.5~
4wt%, more preferably 1 to 3wt%. The Fe content is less than 29wt% and the Ni content is
If it exceeds 40 wt%, the amount of wear will be greater than that of an amorphous magnetic alloy, and uneven wear will become large. Furthermore, when the Fe content exceeds 97.5 wt% and the Ni content becomes less than 1 wt%, the standard potential of the dummy block becomes baser than that of permalloy or the like, resulting in a decrease in corrosion resistance. Furthermore, if the Cr content is less than 1 wt%, the desired effects of the present invention will not be achieved. On the other hand, the dummy block is in the shield case,
It is particularly preferable to bond by spot welding, but if the Cr content exceeds 15wt%, the welding strength will decrease due to an oxide film formed on the surface, and blocks will be damaged during hardening of the resin mold or corner polishing. They may fall off, making it difficult to assemble the head. In addition, if the Cu content is less than 0.5 wt%, the desired effects of the present invention will not be achieved. Moreover, if it exceeds 4 wt%, the amount of deposits that adhere to the surface of the block increases when the coated metal tape runs for a long period of time, and the above-mentioned inconveniences increase. Also, during hot forging, cracks tend to occur, making subsequent rolling and wire drawing impossible. As long as the Fe-Ni alloy in the present invention has Fe, Ni, Cr and Cu contents within the ranges described above, even if it consists only of Fe, Ni, Cr and Mo, It may be made of one or more of Cu and other elements. In such cases, the Fe-Ni alloy contains Fe, Ni, and Cr.
And when it consists only of Cu, the following formula []
It is preferable that the composition is as shown below. Formula [] Fe _a Ni _b Cr _c Cu _dIn the above formula [], a+b+c+d=100wt
%, a is 41 to 97.5 wt%, b is 1 to 40 wt%,
c is 1 to 15 wt%, and d is 0.5 to 4 wt%. In this case, if a is 60 to 86 wt%, b is 10 to 30 wt%, c is 2 to 10 wt%, and d is 1 to 3 wt%, uneven wear will be reduced, corrosion resistance will be improved, frequency characteristics and output level This is preferable in that the deterioration of fluctuations is further reduced. On the other hand, when the Fe-Ni alloy consists of Fe, Ni, Cr, Cu, and one or more other elements, the other elements that may be included include Ti, Zr,
Examples include transition elements such as Hf, V, Nb, Ta, W, Mn, Co, and Zn, and one or more of nonmetallic elements such as Si, Al, and B. The content of one or more of these other elements is 20 wt% or less. The total amount of other added elements is
If it exceeds 20 wt%, the effect of the present invention will be reduced. Such as Fe, Ni and Cr, Cu, and Mo
Fe further containing one or more other elements other than
- The Ni-based alloy contains 29 wt% or more and less than 97.5 wt% Fe, more preferably 60 to 86 wt%, 1 to 40 wt%, more preferably 10 to 30 wt% Ni, and 1 to 15 wt%
%, more preferably 1-3wt% Cu and 20wt%
Hereinafter, in particular, it contains 0.1 to 20 wt% of one or more other elements. Among these, particularly preferred are those having the compositions shown in the following formulas [] to []. Formula [] Fe _a Ni _b Cr _c Cu _d Mn _eIn the above formula [], a+b+c+d+e=
100wt%, a is 39wt% or more and less than 97.5wt%,
b is 1wt% to 40wt%, c is 1 to 15wt%, d is 0.5
~4wt%, e is 2wt% or less. Thus, in addition to Fe, Ni, Cr and Cu,
In Fe-Ni alloys containing Mn, especially when the Mn content c is 0.1wt% or more, the oxidation resistance during hot forging improves, and the surface finish during hot working such as forging improves. In addition, defects during casting are extremely reduced, wear resistance is further improved, and damage to the medium is extremely reduced. In this case, in the above formula [], a is 60~
86wt%, b 10-30wt%, c 2-10wt%, d
When is 1 to 3 wt% and e is 0.1 to 1 wt%, the corrosion resistance during γ-tape running is improved, uneven wear is further reduced, corrosion resistance is further improved, and deterioration of frequency characteristics and output level fluctuations is further reduced. It becomes less. Formula [] Fe _a Ni _b Cr _c Cu _{d Si} fIn the above formula [], a+b+c+d+f=
100wt%, a is 31wt% or more and less than 97.5wt%,
b is 1-40wt%, c is 1-15wt%, d is 0.5-40wt%
4wt%, f is 10wt% or less. Thus, in addition to Fe, Ni, Cr and Cu, Si
Fe-Ni alloys containing
When it is 0.1 wt% or more, castability becomes good, the cast structure is reduced, and wear resistance etc. are further improved. However, if the Si content f exceeds 10 wt%, workability deteriorates and processing such as rolling or wire drawing becomes difficult, so f is 10 wt% or less. In this case, in the above formula [], a is 60~
86wt%, b 10-30wt%, c 2-10wt%, d
When is 1 to 3 wt% and f is 0.1 to 5 wt%, corrosion resistance due to γ-tape running is improved, uneven wear is further reduced, corrosion resistance is further improved, and deterioration of frequency characteristics and output level fluctuations is further reduced. Become. Formula [] Fe _a Ni _b Cr _c Cu _d Mn _e Si _fIn the above formula [], a+b+c+d+e+
f = 100wt%, a is 29wt% or more and less than 97.5wt%, b is 1 to 40wt%, c is 1 to 15wt%, and d is 0.5
~4wt%, e is 2wt% or less, and f is 10wt% or less. In this way, Fe-Ni alloys containing Mn and Si have particularly low Mn and Si contents, respectively.
When it is 0.1wt% or more, both oxidation resistance and castability improve, the surface accuracy and surface defects of the block body are extremely reduced, and the frequency characteristics, output level fluctuations, amount of wear, damage to the medium, etc. are further reduced. Become. In this case, in the above formula [], a is 60~
86wt%, b 10-30wt%, c 2-10wt%, d
is 1-3wt%, e is 0.1-1wt%, f is 0.1-5wt%
As a result, storage stability under high temperature and high humidity conditions and abrasion resistance during γ-tape running are significantly improved, uneven wear is further reduced, and frequency characteristics and output level fluctuations are not deteriorated and media damage is reduced. It becomes extremely small. In order to obtain a dummy block from such an alloy, the master alloy is first melted, for example in a vacuum, and then cast. After this, a forging process is usually performed.
As a result, casting structures or defects are significantly reduced. After that, if necessary, rolling, wire drawing, etc. are performed to adjust the shape, and in some cases, pickling is performed to remove the oxide film, and then cutting, and as necessary, the desired shape is A dummy block is obtained by welding or gluing it to the desired shape and polishing the corners. On the other hand, the core in the magnetic head of the present invention is usually formed from a thin plate of an amorphous magnetic alloy. When an amorphous magnetic alloy is used as a core material, it has good properties as a core, and even after extremely long-term use, there is no difference in the amount of wear between the dummy block and the core, and the media sliding contact of the head is maintained. Good results are obtained in terms of less uneven wear on the surface and less variation in frequency characteristics and output level. When an amorphous magnetic alloy thin plate is used as the core material, its composition may be of various compositions known for use in cores of magnetic heads, but it may have a particularly high saturation magnetic flux density Bs and high retention. The following formula [] is suitable for magnetic magnetic recording media.
It is preferable that the composition is as shown below. Formula [] T _x X _y In the above formula [], T represents Fe and Co or a combination of Fe and Co and one or more other transition metal elements. In this case, if necessary, other additive elements added in combination with Fe and Co are Fe and Co.
other transition metal elements (Sc~Zn; Y~Cd; La
~ Hg; Ac or higher), such as Ni, Ti, Zn,
Hf, V, Nb, Ta, Cr, Mo, W, Mn, Ru,
Specific examples include one or more of Rh, Pd, Os, Ir, and Pt. On the other hand, X represents B, Si and B, or a combination of B or Si and B with one or more other vitrifying elements. In this case, examples of other vitrifying elements added in combination with B or Si and B, if necessary, include one or more of P, C, Ge, Sn, Al, and the like. On the other hand, in the above formula [], x+y=100at
%, and y is 20 to 27at%. That is,
The amount x of the transition metal element whose essential components are Fe and Co is 73 to 80 at%, and the amount y of the vitrification element whose essential components are B or Si and B is 20 to 27 at%.
%. If y is less than 20 at%, it will be difficult to make it amorphous, and if it exceeds 27 at%, the residual magnetic flux density Bs will decrease. Further, the contents of the essential components Fe and Co in the transition metal element components are Fe: 1.5 to 5.6 at% and Co: 45 to 78.5 at%, respectively. Fe content is less than 1.5at% (Co content is 78.5at%)
(larger) or exceeding 5.6 at%, magnetostriction becomes large and magnetic permeability decreases. When Co becomes less than 45at%, Bs decreases. In this case, in the above formula [], T may consist of only Fe and Co, or may consist of Fe, Co, and one or more of the other additive elements mentioned above, within the above content range. When T consists only of Fe and Co, the Fe content is
1.5 to 5.6 at%, more preferably 2 to 5.5 at%, Co content is 67.4 to 78.5 at%, more preferably 67.5 to
It is 78at%. When T contains one or more other elements in addition to Fe and Co, one or more of the other transition metal elements can usually be contained up to a total of 25 at%.
If the content exceeds this range, problems such as decreased Bs and poor surface properties will occur. One example of such an element is Ni. Ni
Addition has the effect of replacing Co and reducing material costs, but as the amount of Ni increases, Bs decreases, so the Ni content is preferably 8 at% or less. On the other hand, one or more other elements may be transition metal elements other than the iron group (Fe, Co, Ni), but the total amount of one or more transition metal elements other than the iron group is 12 at% or less. It is preferable that there be. At this time,
The decrease in Bs is small, and excellent effects unique to each additive element are realized. Such elements include Ru and/or
Or Cr is preferred. In particular, when Ru is added in an amount of 0.5 to 8 at%, wear resistance is improved, and surface properties, punching workability, etc. are improved. Moreover, when 1 to 8 at% Cr is added, corrosion resistance is improved. When Ru of 0.5 to 8 at% and Cr of 1 to 8 at%, especially 2 to 6 at% are added in combination, these effects are further improved and more favorable results are obtained. Furthermore, in addition to these Ru, Cr, Ni, etc., Ta,
It is also possible to contain one or more of Ti, W, Mo, and the like. In addition, in this way, when containing other transition metal elements other than Fe and Co, the total amount of these elements is 20at%.
The Co content is 47.4 to 78.5 at%, more preferably 47.5 to 78 at%, and the Fe content is 1.5 to 78 at%.
It is preferably 5.6 at%, more preferably 2 to 5.5 at%. On the other hand, the vitrification element component X is B or
Contains Si and B as essential components. In this case, when the B content is 3.3 to 27 at% and the Si content is 0 to 16.2 at%, Bs increases, the surface properties of the thin plate improve, and favorable results are obtained. Then, when the B content is 14.1 to 26.9 at% and the Si content is 0.1 to 5.4 at%, Bs becomes even higher,
The surface properties are further improved, and the effect of adding additional elements such as Ru and Cr is also significant, resulting in more favorable results. Note that the vitrification element component X may contain one or more elements other than Si and B, if necessary. However, if the total amount exceeds 0.5at%, it becomes difficult to become amorphous, so the content is
It is preferably 0.5at% or less. A thin plate having a composition as detailed above is an amorphous material having substantially no long-range regularity. Further, the plate thickness is approximately 10 to 200 μm. Such an amorphous magnetic alloy thin plate is manufactured according to a known high-speed quenching method. Such amorphous magnetic alloy thin plates are usually laminated with an insulating adhesive interposed therebetween to form core halves of a desired shape, and these are butted together to form a core half as shown in FIG. 1, for example. , cores 2 and 2'. Alternatively, the thin plates are not laminated, but core halves of a desired shape are formed from the thin plates themselves, and the core halves are butted together to form a core. In addition to forming the cores 2 and 2' from such an amorphous thin plate, it is also effective to form them from sendust. This is because at this time, the hardness or wear resistance of the core and the dummy block described later are similar, uneven wear is reduced, and deterioration of frequency characteristics and output fluctuations is reduced. The magnetic head 1 of the present invention includes the cores 2, 2' and the dummy block 3 as described above, as shown in FIG. 1, FIG. 2, or FIG. 3, for example. That is, for example, cores 2 and 2', which are wound with wire, are placed in a shield case 4 made of permalloy or the like.
Dummy block 3 is stored, and core 2,
2' and dummy blocks 3 are arranged in a predetermined arrangement on the sliding surface of the medium. In this case, the structure and manufacturing method can be based on various known structures and methods. In addition, when the Fe-Ni alloy constituting the dummy block 3 is non-magnetic, as shown in FIGS. The dummy block 3 may be fixedly housed in the case by spot welding or the like, with the dummy block 3 lined with ferromagnetism. It can also be housed by spot welding or the like on the non-magnetic support portion 5 provided in the. Specific Effects of the Invention The magnetic head of the present invention can be used in various applications such as audio, video, measurement, and digital applications. In this case, the dummy block of the magnetic head of the present invention is formed from a Fe-Ni alloy containing a certain amount of Cr and Cu, and the wear resistance of the dummy block is good. Based on this, there is much less deterioration in frequency characteristics, etc. In addition, the corrosion resistance of dummy blocks is extremely high, and tape running problems may occur due to moisture in the air, high temperatures, etc., due to storage, aging, running of the tape under high temperature and high humidity, and even running of coated metal tapes. Moreover, appearance defects and furthermore, frequency characteristic deterioration, etc. do not occur. And, when compared with Fe-Ni alloys that do not contain either Cr or Cu, such effects are
All of them show good values. Furthermore, damage to the medium caused by dummy blocks is extremely small. In addition, the occurrence of crosstalk, induced noise, etc. can be effectively prevented. Further, if the core is made of an amorphous magnetic alloy thin plate, the characteristics of the core will be good, and uneven wear between the core and the dummy block will be further reduced. Specific Embodiments of the Invention Next, more specific embodiments of the present invention are listed.
The present invention will be explained in further detail. Example 1 Fe68.5wt%, Ni23wt%, Cr5wt%, Cu2wt%,
A master alloy with a composition of 0.5wt% Mn and 1wt% Si was vacuum melted and cast into a 40mmφ round bar, which was then cast at 800°C with a casting ratio of 68% to obtain a 13mmφ round bar.
Thereafter, this was rolled into a 3 x 3 mm square bar at 25°C, heat treated in air at 1200°C, pickled, and 3x
It was cut to 4 mm, spot welded into a shield case, and the corners were polished to obtain a dummy block 3 as shown in FIGS. 2 and 3. The atomic composition of the amorphous magnetic alloy thin plate forming the cores 2 and 2' is (Fe _5.5 Co _94.5 ) ₇₂ Ru ₁ Cr ₄
(Si ₁₀ B ₉₀ ) ₂₃ was used to fabricate the magnetic head of the present invention as shown in FIGS. 2 and 3. Using a coating type γ-Fe ₂ O ₃ tape, it was heated at 25℃.
Deterioration of 14KHz/315Hz playback frequency characteristics (dB) and 14KHz recording/playback output level fluctuation (dB) after running at 47.5cm/sec for 500 hours at 60% relative humidity.
was measured.

[Table] For comparison, Table 1 also shows the results when the dummy block 3 was formed from permalloy. In addition, the composition of the amorphous magnetic alloy thin plate forming the cores 2 and 2' is changed to Ru and Cr in the above.
Similar experiments were carried out using materials that did not contain Ru or Cr, or those that added Ti and Ta in addition to Ru and Cr.
Almost the same results were obtained. Example 2 A dummy block with the composition shown in Table 2 below was
It was produced in the same manner as in the example. From these 15 types of dummy blocks, Example 1
Create a magnetic head in exactly the same way as 14KHz/315
When the deterioration of the Hz reproduction frequency characteristic (F characteristic) was measured, the results shown in Table 2 below were obtained. Furthermore, for each of the 15 types of magnetic heads formed from each of these dummy blocks, γ-
Fe ₂ O ₃ tape, running speed 47.5 cm/sec, 25°C,
The amount of wear after running for 500 hours at 60% relative humidity was measured using a surface roughness meter. In addition, after storing for 500 hours at 40℃ and 70% relative humidity, the corrosion layer on the surface of each dummy block was removed.
The amount of corrosion was measured using a surface roughness meter to evaluate corrosion resistance. In addition, γ-Fe ₂ O ₃ tape was applied at 4.75 cm/sec.
Run for 500 hours at 40℃ and 70% relative humidity.
Corrosion resistance was evaluated by measuring the amount of wear after running. Furthermore, a coated metal tape using alloy magnetic powder was run at 4.75 cm/sec at 25° C. and 60% relative humidity for 2000 hours, and the deterioration of the frequency characteristics at 14 KHz/315 Hz was measured. In addition, crosstalk between 125 Hz, 160 nwb/m recording and playback tracks of each magnetic head and induced noise in a 50 Hz, 3 Oe parallel magnetic field were measured. These results are also listed in Table 2 below.

[Table] From the above results, the magnetic head equipped with the dummy block made of the Fe-Ni alloy of the present invention has extremely low frequency characteristic deterioration and output level fluctuation.
It can also be seen that the amount of wear is small, the corrosion resistance due to storage and running is high, and in addition, practically satisfactory values for crosstalk and induced noise can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention. FIG. 2 is a partially omitted perspective view showing another embodiment of the present invention, and FIG. 3 is a partial end view of FIG. 2. 1... Magnetic head, 2, 2'... Core, 3...
dummy block.

Claims (1)

[Scope of Claims] 1. A magnetic head comprising a dummy block and a core, wherein the dummy block has a content of 29 to 97.5 wt%.
of Fe, 1-40wt% Ni, and 1-15wt% Cr
and 0.5 to 4 wt% Cu and no Mo
- A magnetic head characterized by being made of a Ni-based alloy. 2. The magnetic head according to claim 1, wherein the Fe--Ni alloy has a composition represented by the following formula []. Formula [] Fe _a Ni _b Cr _c Cu _d {In the above formula [], a+b+c+d=
100wt%, a is 41-97.5wt%, b is 1-40wt%, c is 1-15wt%, and d is 0.5-97.5wt%.
It is 4wt%. } 3 Fe-Ni alloy contains 29 wt% or more and less than 97.5 wt% Fe, 1 to 40 wt% Ni, and 1 to 15 wt% Cr.
The magnetic head according to claim 1, comprising: 0.5 to 4 wt% of Cu; and 20 wt% or less of one or more other elements. 4. The magnetic head according to claim 3, wherein the Fe-Ni alloy has a composition represented by the following formula []. Formula [] Fe _a Ni _b Cr _c Cu _d Mn _e {In the above formula [], a+b+c+d+e=
100wt%, a is 39wt% or more and less than 97.5wt%,
b is 1-40wt%, c is 1-15wt%, d is 0.5-40wt%
4wt%, e is 2wt% or less. } 5. The magnetic head according to claim 3, wherein the Fe-Ni alloy has a composition represented by the following formula []. Formula [] Fe _a Ni _b Cr _c Cu _d Si _f {In the above formula [], a+b+c+d+f=
100wt%, a is 31wt% or more and less than 97.5wt%,
b is 1-40wt%, c is 1-15wt%, d is 0.5-40wt%
4wt%, f is 10wt% or less. } 6. The magnetic head according to claim 3, wherein the Fe-Ni alloy has a composition represented by the following formula []. Formula [] Fe _a Ni _b Cr _c Cu _d Mn _e Si _f {In the above formula [], a+b+c+d+e+
f = 100wt%, a is 29wt% or more and less than 97.5wt%, b is 1 to 40wt%, c is 1 to 15wt%, and d is 0.5
~4wt%, e is 2wt% or less, and f is 10wt% or less. } 7. The magnetic head according to any one of claims 1 to 6, wherein the core is made of an amorphous magnetic alloy thin plate. 8. The magnetic head according to claim 7, wherein the amorphous magnetic alloy thin plate has a composition represented by the following formula []. Formula [] T _x X _y {In the above formula [], T is Fe and Co,
or a combination of Fe and Co with one or more other transition metal elements; X represents B, or Si and B, or B or a combination of Si and B with one or more other vitrification elements; represent. x+y
= 100 at%, and y is 20 to 27 at%. Furthermore, the amount of Fe is 1.5 to 5.6 at%, and the amount of Co is 45 to 78.5 at%. }