Magnetic film structure

A magnetic film structure comprises at least one magnetic film unit wherein a plurality of main magnetic films of 0.05 to 0.5 .mu.m thickness made of a magnetic alloy containing iron or cobalt as principal constituent and having a high saturation magnetic induction of 10,000 gauss or more and a magnetostriction of 10.sup.-6 or less are laminated through intermediate magnetic films made of a magnetic material such as a nickel and iron alloy or amorphous magnetic alloy different from that of the main magnetic film and being so thin that the influence of coercive force of the intermediate magnetic film does not come out. A plurality of the magnetic film units are also laminated through non-magnetic insulating films. The magnetic film structure has high saturation magnetic induction and low coercive force.

This invention relates to a magnetic film structure having high saturation 
magnetic induction and low coercive force so as to provide good results 
when used for a magnetic head core especially of the type which has 
performance suitable for high density magnetic recording. 
With drastic progress in high density magnetic recording, a metal powder 
tape has been developed which can facilitate attainment of a higher 
coercive force Hc of 1,200 to 1,600 Oe than a coercive force of 600 to 700 
Oe of a conventional iron oxide power tape. In order to obtain 
satisfactory record on such a high coercive force recording medium, a 
magnetic head is required which is made of a magnetic material having a 
high saturation magnetic induction. A magnetic material of an alloy 
containing iron, cobalt or nickel as principal constituent can easily be 
prepared, having a high saturation magnetic induction of 10,000 gauss or 
more. 
Conventionally, when preparing a magnetic head or the like by utilizing a 
metallic magnetic material, magnetic films are laminated with electrical 
insulation therebetween in order to suppress eddy current loss in high 
frequency ranges. The laminated magnetic film structure is prepared by 
so-called thin film formation technique such as sputtering, vacuum 
evaporation, ion plating or plating. 
FIG. 1 shows a prior art laminated magnetic film structure. This known 
laminated structure is prepared by alternate and successive formation of 
magnetic films 10 and non-magnetic insulating films 11 on a non-magnetic 
insulating substrate 13. Each of the magnetic films 10 has a thickness of 
several microns and each of the non-magnetic insulating films 11 has a 
thickness which is about 1/10 of the thickness of the magnetic film 10. 
However, since the crystalline metallic magnetic film behaves itself like 
a columnar structure as shown at 12 in FIG. 1, it is difficult for 
magnetization to move through the boundary of the columnar structure and 
hence the laminated structure exhibits a large coercive force. In a 
magnetic head prepared with the magnetic films of such a large coercive 
force, there arises a problem that a magnetic head core is magnetized when 
a large external magnetic field is applied thereto. 
An approach to this problem is such that magnetic film of a thickness of 
submicrons and non-magnetic films of about 1,000 .ANG. thickness are 
alternately laminated to thereby reduce the coercive force. For example, 
while an about 1 .mu.m thickness single layer film of an alloy of iron and 
6.5 weight % silicon (hereinafter, weight % will be simply referred to as 
%) prepared by sputtering has a coercive force of several oersteds, the 
laminated structure according to the above proposal can reduce the 
coercive force to about 1 Oe. A minimum coercive force obtained with this 
proposed structure will however be 0.8 Oe and for this reason, the 
proposed structure is sometimes unsatisfactory for the magnetic head 
material. 
The following references are cited to show the state of the art; Japanese 
Utility Model Application Laid-open No. 58613/77 and Japanese Patent 
Application Laid-open No. 54408/77. 
An object of this invention is to provide a magnetic film structure having 
a high saturation magnetic induction and a lower coercive force than that 
of the prior art structure. 
Another object of this invention is to provide a magnetic film structure 
for use in a magnetic head which can exhibit an excellent recording and 
reproducing characteristic in relation to a high coercive force recording 
medium. 
Still another object of this invention is to provide a laminated magnetic 
film structure comprised of laminated magnetic films of high saturation 
magnetic induction which can exhibit low coercive force and high 
permeability. 
Specifically, in accordance with teachings of this invention, crystalline 
metallic magnetic films having a high saturation magnetic induction of 
10,000 gauss or more are used for easy formation of a magnetic film 
structure having a low coercive force which can not be obtained from the 
prior art laminated magnetic film structure in which magnetic films and 
non-magnetic insulating films are laminated alternately. 
The inventors of the present application have found that such a magnetic 
film structure can be materialized by replacing the non-magnetic 
insulating intermediate film interposed between adjacent main magnetic 
films in the prior art laminated magnetic film structure with magnetic 
intermediate film different from the main magnetic film. Especially, 
according to the findings, the magnetic intermediate film is preferably 
made of a magnetic material having a relatively low coercive force (less 
than 10 Oe) and a low magnetostriction (less than 10.sup.-6). 
Thus, in the magnetic film structure according to the present invention, a 
plurality of main magnetic films of a predetermined thickness made of a 
metallic magnetic alloy having high saturation magnetic induction and low 
magnetostriction are laminated through intermediate magnetic films of a 
predetermined thickness made of a magnetic material different from that of 
the main magnetic films. 
FIG. 2 shows, in sectional form, a magnetic film structure according to 
this invention. As shown, the magnetic film structure comprises main 
magnetic films 20 made of a magnetic alloy containing, for example, iron 
or cobalt as principal constituent and having a high saturation magnetic 
induction, intermediate magnetic films 21 made of an alloy having 
relatively low coercive force and magnetostriction, for example, a nickel 
and iron alloy (permalloy) or amorphous magnetic alloy, and a non-magnetic 
substrate 23. 
The intermediate magnetic film 21, when made of the alloy, is very thin, 
amounting to 30 to 500 .ANG. and the main magnetic film 20 has such a 
thickness as not to be greatly affected by the adverse magnetism of its 
columnar crystalline structure 22. Consequently, the columnar crystalline 
structure 22 of the main magnetic film 20 can be sectonalized by the 
intermediate magnetic film 21. With this magnetic film structure, the 
magnetization which is otherwise oriented in a direction vertical to the 
film surface along the columnar structure and the magnetization which is 
also otherwise difficult to move through the boundary of the columnar 
structure are both oriented to the interior of the film so as to have 
ability to move within the film under the application of a small magnetic 
field, thereby reducing the coercive force. In addition, the intermediate 
magnetic films 21 presumably assist in aiding the magnetic coupling 
between the respective main magnetic films 20 to enhance the movement of 
the magnetization. 
Specifically, it is recommended that the main magnetic film of this 
invention be made of either a magnetic alloy containing iron as principal 
constituent and one or more elements selected from a group of silicon, 
aluminum and titanium by 1 to 30% in total or a magnetic alloy containing 
cobalt as principal constituent and one or more elements selected from a 
group of iron, vanadium, titanium and tin. Either alloy has a low 
magnetostriction (less than 10.sup.-6) and a high saturation magnetic 
induction (more than 10,000 gauss). If the magnetostriction exceeds 
10.sup.-6, the magnetic characteristic disadvantageously will become 
increasingly irregular under the application of stress and if the 
saturation magnetic induction is not greater than 10,000 gauss, 
satisfactory recording on a medium of large coercive force will 
disadvantageously be prevented. For the sake of improving corrosion-proof 
and abrasion-proof properties and controlling magnetostriction, the alloy 
composition of the main magnetic film may be added with an additive by 
less than 10%. When the magnetic film structure is used in a magnetic head 
associated with a magnetic recording medium having a high coercive force 
of 1,200 Oe or more, the main magnetic film preferably has a saturation 
magnetic induction of more than 10,000 gauss and a coercive force of less 
than 10 Oe. 
On the other hand, the intermediate magnetic film made of a nickel and iron 
alloy (permalloy) or amorphous magnetic alloy preferably has an alloy 
composition which exhibits a low coercive force (less than 10 Oe) and a 
low magnetostriction (less than 10.sup.-6). However, as far as the 
magnetic material of the intermediate magnetic film is different from that 
of the main magnetic film, namely, the former material contains an element 
as principal constituent different from that of the latter material or has 
an atomic configuration different from that of the latter material, 
attainment of effects of the present invention can be expected. If the 
same alloy is used for both the intermediate and main magnetic films, the 
columnar structure of the intermediate magnetic film and that of the main 
magnetic film are linked together and good results can not be obtained. 
The amorphous magnetic alloy is free from this problem and preferably 
employed in the present invention. 
If the intermediate magnetic film is excessively thick, then the influence 
of its coercive force becomes predominant, thus making it difficult to 
materialize a laminated magnetic film structure having low coercive force 
and high permeability. Accordingly, the thickness of the intermediate 
magnetic film is selected to a value which can substantially eliminate the 
influence of its coercive force upon the laminated magnetic film 
structure. Thus, with the intermediate magnetic film having a low coercive 
force (less than 10 Oe) and a thickness of 30 to 500 .ANG. as described 
above, a fine structure of multilayer magnetic films can be realized 
relatively easily. For example, when a magnetic material having a 
relatively high coercive force such as cobalt or nickel is used for the 
intermediate magnetic film, it is preferable that the thickness of the 
intermediate magnetic film be 10 to 80 .ANG.. 
As described above, the magnetic film structure of the present invention 
preferably has a laminated structure comprising a plurality of main 
magnetic films containing iron or cobalt as principal constituent and 
having a high saturation magnetic induction, and intermediate magnetic 
films made of a nickel and iron alloy or amorphous magnetic alloy and each 
interposed between adjacent main magnetic films. 
The present invention can effectively improve a crystalline magnetic film 
structure in which the magnetic film exhibits the columnar (or 
needle-like) structure when it takes the form of a single-layer film. In 
particular, the coercive force can be reduced by about one order by 
applying teachings of the present invention to a magnetic film structure 
in which the magnetic film in the form of a single layer has a coercive 
force of the order of several oersteds. 
Preferably, the thickness of each main magnetic film ranges from 0.05 .mu.m 
to 0.5 .mu.m, most preferably, 0.05 .mu.m to 0.3 .mu.m. For the thickness 
being less than 0.05 .mu.m, the magnetic characteristic of the 
intermediate magnetic film comes out and if the intermediate magnetic film 
is reduced in thickness, film homogeneity will be impared to prevent 
realization of a stable fine structure. For the thickness being more than 
0.5 .mu.m, the influence of the columnar structure becomes predominant to 
increase the coercive force. 
Preferably, the thickness of each intermediate magnetic film ranges from 30 
.ANG. to 500 .ANG., most preferably, 50 .ANG. to 300 .ANG. when the 
intermediate magnetic film is made of the nickel and iron alloy or 
amorphous magnetic alloy, having a coercive force of 10 Oe or less. For 
the thickness being less than 30 .ANG., effects of the magnetic properties 
of the intermediate magnetic film are diluted whereas for the thickness 
being more than 500 .ANG., the magnetic characteristic of the intermediate 
magnetic film is enhanced to increase the coercive force. For the same 
reasons, the intermediate magnetic film preferably has a thickness which 
ranges from 10 .ANG. to 80 .ANG., most preferably, 15 .ANG. to 70 .ANG. 
when it is made of a material having a relatively high coercive force such 
as cobalt. The laminated magnetic film structure of the present invention 
wherein the main magnetic films and the intermediate magnetic films are 
laminated as described previously can provide a lower coercive force than 
that of the prior art laminated magnetic film structure wherein the main 
magnetic films and the non-magnetic insulating intermediate films are 
laminated. 
Preferably, the intermediate magnetic film is made of a nickel and iron 
alloy having a magnetostriction of 1.times.10.sup.-6 or less which 
contains, for example, about 81% nickel and about 91% iron. When the 
intermediate magnetic film is made of an amorphous magnetic alloy, it is 
preferable that, for example, cobalt be added with one or more elements 
selected from a group of zirconium, titanum, molybdenum, niobium, 
tungsten, aluminum, nickel, chromium, silicon and boron or cobalt, iron 
and nickel be added with silicon, boron and phosphorus, respectively, to 
provide a coercive force of several oersteds or less. The addition of such 
additives as above is not limitative. In the case of the amorphous 
magnetic alloy, crystallization takes place as the temperature rises 
beyond a crystallization temperature and the coercive force increases 
abruptly. As a result, it happens that the magnetic characteristic of the 
intermediate magnetic film comes out to increase the coercive force of the 
laminated magnetic film structure to an undesirable extent. Therefore, the 
crystallization temperature is desired to be high. 
Generally, when the coercive force of the intermediate magnetic film 
exceeds 10 Oe, the prepared laminated magnetic film structure is affected 
by the excessive coercive force, making it difficult to obtain a low 
coercive force. 
The number of laminated main magnetic films and intermediate magnetic films 
is determined in accordance with the thickness of the laminated magnetic 
film structure adapted for utilization and purpose of the structure and 
the thus determined number cooperates with the thickness of each film to 
provide an intended characteristic. 
In accordance with teachings of the present invention, a thick laminated 
magnetic film structure having excellent high frequency magnetic 
properties can also be materialized by laminating a predetermined number 
of laminated magnetic film units of a suitable thickness each comprised of 
the main magnetic films and intermediate magnetic films through 
non-magnetic insulating films such as SiO.sub.2 films or Al.sub.2 O.sub.3 
films having electrical insulation. The number of the laminated films in 
the laminated magnetic film unit and the number of the laminated magnetic 
film units in the thick laminated magnetic film structure are determined 
in accordance with the thickness of the thick laminated magnetic film 
structure adapted for utilization and purpose of the structure and the 
thus determined number cooperates with the thickness of the main magnetic 
film, intermediate magnetic film and non-magnetic insulating film to 
provide an intended characteristic. 
The non-magnetic insulating film normally has a thickness which ranges from 
0.05 .mu.m to 1 .mu.m. For the thickness being more than 1 .mu.m, the 
magnetic properties such as permeability are degraded whereas for the 
thickness being less than 0.05 .mu.m, the formation of a complete film 
becomes difficult, resulting in insufficient interlayer insulation. 
Each of the laminated magnetic film units to be laminated through the 
non-magnetic insulating films normally has 10 to 50 main magnetic films 
which are laminated through the intermediate magnetic films. Preferably, 
about 30 main magnetic films are used to obtain a thick laminated magnetic 
film structure having excellent high frequency magnetic properties.

The invention will now be described by way of example. 
An RF sputtering apparatus as shown in FIG. 3 is used for preparing the 
magnetic film structure. Three independent sets of opposing electrodes are 
provided inside a vacuum container 30. Electrodes 31, 32 and 33 are target 
electrodes (cathodes). An alloy target containing iron or cobalt as 
principal constituent for formation of the main magnetic film is disposed 
on the electrode 31, an alloy target made of an nickel and iron alloy 
(permalloy) or amorphous magnetic alloy for formation of the intermediate 
magnetic film is disposed on the electrode 32, and a target made of an 
insulating material such as SiO.sub.2 or Al.sub.2 O.sub.3 for formation of 
the non-magnetic insulating film is disposed on the electrode 33. 
Electrodes 34, 35 and 36 respectively provided directly beneath the 
electrodes 31, 32 and 33 are substrate electrodes (anodes). A specimen 37 
may be carried on any one of the substrate electrodes as necessary. Also, 
if necessary, a magnetic field may be applied in parallel to the surface 
of the specimen 37 by means of electromagnets 38 and 38' during sputtering 
so that the direction of easy magnetization of the magnetic film structure 
to be formed may be oriented in parallel to the surface of the film. 
Electric discharge is effected within an atmosphere of argon gas which is 
introduced into the vacuum container 30 via a gas inlet pipe 39. An 
evacuation pipe 40 is provided for the vacuum container 30, and a switch 
41 is adapted to switch the electrodes. 
EXAMPLE 1 
Preparation of an iron and 6.5% silicon film standing for the main magnetic 
film will first be described. 
The following are various condition selected for sputtering under a 
relatively good condition. 
______________________________________ 
Target composition iron and 7.5% silicon 
RF power density 2.8 W/cm.sup.2 
Argon pressure 2 .times. 10.sup.-2 Torr 
Substrate temperature 
350.degree. C. 
Anode-cathode separation 
25 mm 
distance (representing 
hereinafter the distance between 
target electrode and substrate 
electrode) 
Film thickness 1.5 .mu.m (for reference) 
0.1 .mu.m (this example) 
______________________________________ 
A single layer film of 1.5 .mu.m thickness thus formed on the non-magnetic 
substrate has magnetic properties including a coercive force Hc of 2.5 Oe, 
a permeability .mu. of 400 at 5 MHz, and a saturation magnetic induction 
of 18,500 gauss. Sputtering is effected under the application of a 
magnetic field (about 10 Oe) oriented in one direction parallel to the 
surface of the magnetic film. These magnetic properties are measured in 
the direction of hard magnetization which is vertical to the surface of 
the magnetic film. A glass substrate is used as the non-magnetic 
substrate. Of various conditions for sputtering, the silicon content in 
the targe must be excessive since the composition in a resulting sputtered 
film tends to shift to the iron content in comparison with the composition 
in the target. As the RF power density increases beyond 2 W/cm.sup.2, the 
coercive force Hc tends to decrease. The substrate temperature is 
preferably above 250.degree. C. to mitigate stress in the film. As the 
anode-cathode separation distance decreases, the coercive force tends to 
become low but in consideration of stability of electric discharge during 
sputtering, the distance is preferably about 20 to 30 mm. Preferably, the 
vacuum container is highly evacuated to a vacuum degree of the order of 
10.sup.-7 Torr prior to the introduction of argon gas since the remaining 
oxygen and impurity will adversely affect the magnetic properties of the 
magnetic film structure. 
Typically, the intermediate magnetic film is prepared by RF sputtering 
under the following conditions. 
______________________________________ 
Target material 83% nickel and 17% iron 
RF power density 0.5 W/cm.sup.2 
Argon pressure 5 .times. 10.sup.-3 Torr 
Substrate temperature 
250.degree. C. 
Anode-cathode separation 
50 mm 
distance 
Film thickness 100 .ANG. 
______________________________________ 
A thus prepared intermediate magnetic film approximately has a composition 
of 81% nickel and 19% iron. A laminated magnetic film structure having 15 
laminated main magnetic films is thus prepared, having a total thickness 
of about 1.5 .mu.m with each of the main magnetic films formed in 0.1 
.mu.m thickness and each of the intermediate magnetic films formed in 100 
.ANG. thickness. 
Another intermediate magnetic film is prepared by using an amorphous 
magnetic alloy under the following conditions. 
______________________________________ 
Target material Co.sub.80 Mo.sub.9.5 Zr.sub.10.5, 
Co.sub.82 Nb.sub.13 Zr.sub.5, 
Co.sub.59 W.sub.5 Zr.sub.6, 
Co.sub.81 Ti.sub.19 
RF power density 0.8 W/cm.sup.2 
Argon pressure 5 .times. 10.sup.-3 Torr 
Substrate temperature 
150.degree. C. 
Anode-cathode separation 
50 mm 
distance 
Film thickness 100 .ANG. 
______________________________________ 
For reference, an intermediate magnetic film of SiO.sub.2 or molybdenum is 
also prepared. 
When preparing the intermediate magnetic film by using the amorphous 
magnetic alloy, the substrate temperature is set to 250.degree. C. during 
sputtering of the main magnetic films. 
Table 1 shows magnetic properties of the laminated magnetic film structure 
having the thus prepared main magnetic films of iron and 6.5% silicon 
alloy and various kinds of intermediate magnetic films as listed in Table 
1. Magnetic properties of a plurality of structures immediately after 
sputtering are averaged and indicated in Table 1. Item (a) represents 
properties of single layer films of iron and 6.5% silicon alloy, items (b) 
and (c) represent properties of laminated magnetic film structures having 
the prior art non-magnetic insulating intermediate films, and items (d) to 
(h) represent properties of laminated magnetic film structures having 
intermediate magnetic films of permalloy or amorphous magnetic alloy 
according to teachings of the present invention. As will be seen from the 
results shown in Table 1, the laminated magnetic film structures having 
the intermediate magnetic films according to the invention have an 
extremely lower coercive force than that of the prior art laminated 
magnetic film structures having the non-magnetic insulating intermediate 
films. Specifically, according to the present invention, the coercive 
force is reduced to below 0.5 Oe to provide a practically significant 
permeability. 
TABLE 1 
______________________________________ 
Magnetic properties 
Satura- 
Permea- tion 
Coercive 
bility magnetic 
force .mu. (at induction 
Hc(Oe) 5 MHz) Bs(G) 
______________________________________ 
(a) Single layer film 
2.5 400 18,500 
Intermed- 
Non-magnetic 
iate films of 
material 
laminated 
(b) SiO.sub.2 1.0 2,000 18,000 
structure 
(c) Mo 0.9 900 18,000 
(d) Ni--19% Fe 
0.4 2,400 18,000 
Amorphous magnetic 
alloy 
(e) 0.4 2,400 17,000 
Co.sub.80 --Mo.sub.9.5 --Zr.sub.10.5 
(f) Co.sub.82 --Nb.sub.13 --Zr.sub.5 
0.45 2,450 18,000 
(g) Co.sub.89 --W.sub.5 --Zr.sub.6 
0.5 2,200 18,500 
(h) Co.sub.81 --Ti.sub.19 
0.4 2,100 17,000 
______________________________________ 
According to the present invention, each of the main magnetic films can 
have a thickness which ranges from 0.05 .mu.m to 0.5 .mu.m to ensure that 
the columnar structure can be sectionalized to an extent that the magnetic 
properties of the laminated magnetic film structure are not affected 
adversely. 
FIG. 4 shows the relation between the thickness of the intermediate film or 
spacer, coercive force Hc and permeability .mu. at 5 MHz when the main 
magnetic film of iron and 6.5% silicon alloy has a thickness of 0.1 .mu.m 
and the intermediate magnetic film is made of permalloy. The laminated 
magnetic film structure has 15 main magnetic films and the intermediate 
magnetic films interposed between adjacent main magnetic films. It will be 
seen from FIG. 4 that the coercive force is about 0.8 Oe for the thickness 
of the intermediate magnetic film which ranges from 30 .ANG. to 500 .ANG., 
is less than 0.5 Oe for the thickness range of 50 to 300 .ANG. and is 
minimum near 100 .ANG.. The permeability, on the other hand, becomes 
maximum near 100 .ANG.. Although the influence of the thickness of the 
intermediate magnetic film slightly differs depending on the type of 
material of the intermediate magnetic film and the thickness of each of 
the main magnetic films, the range for preferable coercive force 
substantially coincides with the range for preferable permeability. For 
the thickness being less than 30 .ANG., the magnetic properties of the 
intermediate magnetic film are diluted to increase the coercive force 
whereas for the thickness being less than 10 .ANG., it is difficult to 
block the columnar structure in the main magnetic film, allowing the 
columnar structure to grow, whereby the effects of the present invention 
are degraded. 
For the thickness of the intermediate magnetic film being more than 500 
.ANG., on the other hand, the magnetic properties of the intermediate 
magnetic film comes out to increase the coercive force and decrease the 
saturation magnetic induction of the main magnetic film even when the main 
magnetic film inherently has a high saturation magnetic induction. Since 
the thickness of the intermediate magnetic film is difficult to directly 
measure, it is calculated from theoretical sputtering rate when the alloy 
is deposited to a thickness of several microns and controlled in terms of 
time. 
Because of the coercive force of the intermediate magnetic film being less 
than 10 Oe in this example, the thickness can be set to a range which is 
relatively easy to control, bringing out significant, practical effects. 
In this example, a magnetic field is applied in one direction parallel to 
the surface of the main magnetic film during sputtering so that the 
direction of easy magnetization is established which coincides with the 
direction of the applied magnetic field. As shown in FIG. 5, when the 
frequency of magnetic field is varied, the permeability (represented by 
curve 51) is measured in the direction of the applied magnetic field 
(direction of easy magnetization) and the permeability (represented by 
curve 52) is measured in the direction vertical to the applied magnetic 
field (direction of hard magnetization). It will be seen that the latter 
permeability is higher than the former. Accordingly, in a magnetic head 
incorporating the laminated magnetic film structure of the present 
invention, its direction of hard magnetization can be arranged in an 
advantageous direction with respect to a magnetic circuit for the magnetic 
head. 
EXAMPLE 2 
Another example of the present invention will be described hereunder. 
For example, when sputtering a target of cobalt and 12% iron alloy under 
the following conditions to prepare a laminated magnetic film structure 
having main magnetic films of cobalt and 12% iron alloy, a resulting 
single layer structure exhibits a coercive force of several of tens of 
oersteds whereas a resulting structure according to the present invention 
exhibits a coercive force which is reduced to 1 Oe or less. Since the 
cobalt and iron alloy inherently has a high coercive force, the film 
thickness needs to be reduced slightly. 
______________________________________ 
Target composition Co--12% Fe 
RF power density 2.5 W/cm.sup.2 
Argon pressure 1 .times. 10.sup.-3 Torr 
Substrate temperature 150.degree. C. 
Anode-cathode separation 
30 mm 
distance 
Thickness of Co-Fe alloy 
0.05 .mu.m 
film 
Composition of intermediate 
Co.sub.80 Mo.sub.10 Zr.sub.10 
film 
Thickness of intermediate 
80 .ANG. 
film 
The number of laminated 
10 
Co-Fe alloy films 
The number of intermediate 
9 
films 
Coercive force Hc of laminated 
1 Oe 
magnetic film structure 
Saturated magnetic induction 
15,000 gauss 
of laminated magnetic film 
structure 
______________________________________ 
Similar results can be obtained with intermediate magnetic films of 
permalloy. Sputtering conditions for the intermediate magnetic film are 
the same as those in Example 1. 
The foregoing Examples 1 and 2 clearly indicate that satisfactory effects 
can be attained whenever the main magnetic film used in the present 
invention is made of the magnetic alloy which contains iron or cobalt as 
principal constituent and has a high saturation magnetic induction (more 
than 10,000 gauss) and a magnetostriction of nearly zero. Especially, in a 
magnetic film structure wherein the magnetic film prepared by thin film 
formation technique exhibits a columnar structure which is vertical or 
oblique to the film surface, the present invention can reduce the coercive 
force, thereby providing a laminated magnetic film structure suitable for 
use in a magnetic head. 
EXAMPLE 3 
FIG. 6 shows still another example of the film structure according to the 
present invention which is a thick laminated magnetic film structure. In 
this example, a plurality of laminated magnetic film units (prepared in 
accordance with Examples 1 and 2) each comprised of alternate lamination 
of main magnetic films 20 and intermediate magnetic films 21 and having a 
thickness of about 5 microns are laminated on a non-magnetic substrate 23 
through second intermediate films of 0.1 .mu.m thickness made of a 
non-magnetic insulating material such as SiO.sub.2 or Al.sub.2 O.sub.3. 
The thus prepared thick laminated magnetic film structure is free from 
degradation of permeability in high frequency ranges, thus providing an 
excellent magnetic head core. In particular, this thick laminated magnetic 
film structure can be used in a video head having a track width of 10 
.mu.m or more. 
FIG. 7 shows a magnetic head in which two thick laminated magnetic film 
structures formed on respective non-magnetic substrates and machined into 
a predetermined configuration are mated together so that magnetic gap 
surfaces oppose to each other. A magnetic film structure 62 is formed on a 
first non-magnetic substrate 61, and a second non-magnetic substrate 63 
adapted to protect the magnetic film structure is bonded by glass, for 
example, to the first substrate or the magnetic film structure. Denoted by 
64 is a magnetic gap and 65 is a window for coil winding. In this example, 
the thickness of the laminated magnetic film structure 62 corresponds to 
the track width. 
FIGS. 8a and 8b show a magnetic recording thin film head incorporating the 
laminated magnetic film structure according to the invention, where FIG. 
8a illustrates a sectional view of a magnetic head core and FIG. 8b a top 
view thereof. In FIGS. 8a and 8b, there are illustrated a non-magnetic 
substrate 71, a lower magnetic film structure, an upper magnetic film 
structure, a conductor coil 74 and a magnetic gap 75. In this example, the 
thickness of the magnetic film structure being less than several microns 
suffices and the non-magnetic insulating film 24 as required for the FIG. 
6 example can be dispensed with. 
Other effects brought about by the present invention will now be described 
with reference to FIGS. 9a and 9b which illustrate, in fragmentary 
enlarged form, a portion of the magnetic film structure near the magnetic 
gap of the magnetic head shown in FIGS. 8a and 8b. More particularly, 
illustrated in FIG. 9a are magnetic film structures 72 and 73 which are 
constituted by a single-layer film having a large columnar structure 
according to the prior art. In this case, the columnar structure is 
disturbed at bent portions 76 and 77, causing cracks or corrosion thereat. 
In addition, stress is concentrated at the bent portions to create cracks 
thereat. In contrast thereto, in the case of the magnetic head 
incorporating the laminated magnetic film structures according to the 
present invention, the crystalline structure is fine and uniformly 
continuous at the bent portions as shown in FIG. 9b, so that stress 
concentration at the bent portions can be reduced to suppress the creation 
of cracks, thereby ensuring provision of a highly corrosion-proof magnetic 
circuit. 
Obviously, many modifications and variations of the present invention are 
possible in the light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described.