Magnetic thin film and thin film magenetic element using the same

A magnetic thin film is disclosed which has a composition represented substantially by the following chemical formula and, the same time, has the whole or part of the thin film formed of an amorphous region: EQU {(Fe.sub.1-x Co.sub.x).sub.1-y (B.sub.1-z X.sub.z).sub.y }.sub.1-a RE.sub.a wherein X represents at least one element selected from among the Group 4B elements in the CAS version of the Periodic Table, RE represents rare earth elements including Sm, and x, y, z, and a represent numerical values satisfying the following expressions, 0<x<1, 0<z<1, 0.05<y<0.36, and 0<a.ltoreq.0.1.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a magnetic thin film to be used for such planar 
magnetic elements as, for example, planar inductors and planar 
transformers and a thin film element using the magnetic thin film. 
2. Description of the Related Art 
In recent years, the miniaturization of various electronic devices has been 
being promoted strenuously. The miniaturization of power source parts of 
the electronic devices, however, has been advancing slowly by comparison. 
The volume ratio of such power source parts to their relevant devices 
proper has been steadily on the increase. The miniaturization of 
electronic devices owes greatly to the evolution of LSI's for various 
circuits. Such magnetic parts as inductors and transformers which are 
essential to the power source parts, however, have been delayed in 
miniaturization and circuit integration. This delay constitutes itself a 
main cause for the increase in the volume ratio mentioned above. 
For the solution of this problem, planar magnetic elements which combine 
planar coils with magnetic members have been proposed. A study is now 
under way with a view to improving the planar magnetic elements in 
performance. The magnetic thin films to be used in the planar magnetic 
elements are required to have low loss and enjoy high saturation 
magnetization in a high frequency zone exceeding 1 MHz. In the high 
frequency zone, the permeability is chiefly obtained during the process of 
rotational magnetization. For the acquisition of an ideal process of 
rotational magnetization, the excitation must be made in the direction of 
the axis of hard magnetization under the condition of uniform inplane 
uniaxial magnetic anisotropy. The permeability, coercive force, and the 
like in the direction of the axis of hard magnetization constitute 
themselves the important physical properties. 
The permeability in the high frequency zone is a magnitude which is related 
complicatedly to the various physical properties of a sample. As the most 
related of these physical properties, the anisotropic magnetic field is 
cited. The permeability in the high frequency zone is roughly proportional 
to the reciprocal of the anisotropic magnetic field. In such magnetic 
elements as, for example, a thin film inductor, the optimum permeability 
varies, depending on the particular design of an element. For the purpose 
of enabling a magnetic element like a thin film inductor to realize high 
permeability suitable therefor in a high frequency zone, therefore, the 
magnetic element must possess uniaxial anisotropy within the plane of the 
magnetic film and also possess an ability to control the anisotropic 
magnetic field. 
Further, since the magnetic element like a thin film inductor can expect 
the electric power and the saturated current available therefor to be 
exalted in proportion as the saturation magnetization of the magnetic film 
is increased, high saturation magnetization is also necessary for the 
magnetic film used in the magnetic element like a thin film inductor. It 
is natural that a magnetic thin film satisfying both the requirements of 
low loss and high saturation magnetization in a high frequency zone is 
effective in a thin film magnetic head as the recording density is 
increased and the coercive force, energy integral, and operating frequency 
of the medium are heightened. These requirements generally apply to the 
other magnetic elements. 
When the magnetic thin film mentioned above is used in the form of a single 
layer or a laminate in the magnetic element like a thin film inductor, the 
magnetic properties thereof are varied to a certain extent from those 
inherent in the individual magnetic thin film. This variation has been 
posing a problem. 
When numerous magnetic elements are formed on a substrate by the standard 
thin film processing technique, it often happens that the magnetic thin 
film is underlaid by either one layer or a laminate of a plurality of 
layers, selected from among resin layer, insulating undercoating film 
layer, electroconductive metal film layer, protective film layer, adhesive 
film layer, and mask grade layer intended for the work of patterning 
besides a substrate wafer. It is also common that such various layers as 
mentioned above are superposed on the magnetic thin film after this 
magnetic thin film has been formed completely. For the formation of each 
of these layers, such steps as PVD or CVD, plating, application by the use 
of a spin coater, and baking for the sake of curing are sequentially 
carried out. Even when the film formation on the substrate at an elevated 
temperature is not involved at the step of PVD or CVD, the temperature 
rise to a certain extent generally occurs during the deposition of a film. 
Further, the magnetic film and part or the whole of the component layers as 
well must be subjected to the patterning work for the purpose of 
implementing the formation of electrodes, the formation of slits in the 
magnetic film, the formation of through holes, the separation of the 
component elements, and the designing of magnetic circuits. Generally, the 
patterning work is carried out by the steps of forming a mask by any of 
various techniques available therefor and dry etching or wet etching a 
pertinent layer with the aid of the mask. 
More often than not, the various treatments possibly result in impairing 
the flatness and smoothness of the surface or interface of the magnetic 
thin film and causing a change in shape such as through the introduction 
of a periodic undulation. Since the stress which is exerted in the form of 
contacting force on the magnetic thin film through the surface or 
interface is varied and this stress is also varied in magnitude and 
direction from one place to another of the film. Frequently, the stress is 
dispersed in the two factors, magnitude and direction. The change in shape 
and the change in stress both affect the magnetic properties of the 
magnetic thin film. Particularly, the latter change demands the greatest 
attention from the viewpoint of homogenizing necessary magnetic 
characteristics to the magnetic thin film and controlling the homogenous 
magnetic characteristics and also from the viewpoint of enabling the 
magnetic thin film to retain soft magnetism. 
The magnetic anisotropy of the magnetic thin film responds to the strain 
caused in the magnetic thin film by stress. When anisotropic stress is 
generated, magnetic anisotropy which corresponds thereto is consequently 
induced. When the dispersion of stress mentioned above occurs, the 
magnetic anisotropy is induced to be dispersed in response to the 
dispersion of stress. This dispersion of the magnetic anisotropy generally 
increases the coercive force and impairs the soft magnetism of the 
magnetic thin film. The energy of the induced magnetic anisotropy is 
proportional to the magnetostriction constant. 
For the purpose of enabling the magnetic thin film in a thin film magnetic 
element to manifest necessary magnetic properties as designed, therefore, 
it is necessary either to decrease the anisotropic stress induced by the 
process of manufacture of the magnetic element or to utilize positively 
the anisotropic stress generated by the through process of the individual 
magnetic element for the control of the anisotropy. The positive 
utilization of the anisotropic stress for the control of anisotropy, 
however, is technically difficult. The control of this nature is not 
easily realized. As respects the dispersion of magnetic anisotropy which 
impairs the soft magnetism, it is necessary either to elucidate the 
mechanism of this dispersion and lower the dispersion itself or to 
decrease the intrinsic stress itself. 
These measures are approaches from the manufacturing process side. From the 
magnetic thin film side, the decrease of the magnetostriction constant 
forms an effective countermeasure. The material of the magnetic thin film 
for use in the thin film magnetic element more often than not has a 
relatively large magnetostriction constant when it fulfills such 
requirements as high saturation magnetization and thorough inplane 
uniaxial magnetic anisotropy which the magnetic thin film is expected to 
possess. Since the spontaneous magnetization is decreased when such a 
substance as Si is added in a stated amount for the sake of diminishing 
positive magnetostriction, it is necessary to effect the decrease of the 
magnetostriction while repressing to the smallest possible limit the 
spontaneous magnetization decrease meanwhile. 
As mentioned above, the magnetic elements adapted for miniaturization are 
badly in need of a magnetic thin film which possesses a small 
magnetostriction constant and exhibits such magnetic properties as are not 
readily affected by the process of manufacture of a magnetic element while 
fulfilling the requirements, i.e. high saturation magnetization of the 
magnetic layer, soft magnetism, and ability to control inplane uniaxial 
magnetic anisotropy. 
SUMMARY OF THE INVENTION 
This invention, undertaken for the purpose of fulfilling the task and 
intended particularly to diminish the magnetostriction without impairing 
the high saturation magnetization, aims to provide a magnetic thin film 
which possesses a small magnetostriction constant and exhibits such 
magnetic properties as are not readily affected by the process of 
manufacture of a magnetic element while fulfilling the requirements, i.e. 
high saturation magnetization of the magnetic layer, soft magnetism, and 
ability to control inplane uniaxial magnetic anisotropy and a thin film 
magnetic element using the magnetic thin film. 
The magnetic thin film of this invention is characterized by being formed 
of a magnetic substance comprising a transition metal consisting of Fe and 
Co, B, at least one element selected from among the Group IVB elements 
such as, C, Si, and Sn in the IU version of the Periodic Table, rare 
earth elements including Sm, and inevitable impurities and satisfying the 
following compositional formula and the whole or part of the region of 
construction comprising an amorphous region. 
Compositional formula: {(Fe.sub.1-x Co.sub.x).sub.1-y (B.sub.1-z 
X.sub.z).sub.y }.sub.1-a RE.sub.a wherein X represents at least one 
element selected from among the Group IVB elements in the IU version of 
the Periodic Table, RE represents rare earth elements including Sm, and x, 
y, z, and a satisfy the following expressions, 0&lt;x&lt;1, 0&lt;z&lt;1, 0.05&lt;y&lt;0.36, 
and 0.ltoreq.a&lt;0.1. 
With the construction satisfying this composition, this invention realizes 
a soft magnetic thin film which retains high saturation magnetization, low 
loss, and ability to control inplane uniaxial magnetic anisotropy and, at 
the same time, suffers the magnetic properties thereof to be varied and 
deteriorated only slightly by the stress exerted by the manufacturing 
process of an element on the magnetic film during or after the manufacture 
and a thin film magnetic element using the soft magnetic thin film. 
Now, the manner for implementing this invention will be described below. 
The magnetic thin film of the present invention possesses a composition 
substantially represented by the compositional formula mentioned above and 
has the whole or part of the region of the construction of the film formed 
of an amorphous region. The transition metal consisting of Fe and Co which 
is a component for supporting magnetism may be Fe alone, Co alone, or an 
Fe--Co combination. It is particularly advantageous to use the Fe--Co 
combination because this combination acquires a high saturated magnetic 
flux density and, at the same time, exhibits a high Curie temperature. 
B and the Group IVB elements such as C, Si, and Sn in the IU version of 
the Periodic Table constitute a component which promotes the impartation 
of an amorphous texture to the magnetic thin film and, at the same time, 
contributes to the improvement of the temperature of crystallization and 
the magnetic anisotropy. If the amount of this component is unduly small, 
the necessary effects will not be obtained. If the amount of this 
component plus the transition metal mentioned above exceeds 36 at %, the 
decrease of spontaneous magnetization will be conspicuous and the magnetic 
properties aimed at will not be easily acquired. 
The rare earth elements including Sm are the elements which, when added 
even in a minute amount, lower the positive magnetostriction without 
substantially impairing the soft magnetic properties of the thin film. 
When they are added in an unduly large amount, the spontaneous 
magnetization will be possibly degraded. Appropriately, the amount of 
these rare earth elements to be added is in the range of not more than 10 
at %, based on the amount of Fe, Co, B, and X mentioned above. 
Particularly, Sm has a conspicuous effect. Preferably, the amount of Sm is 
not less than 50% of the total number of mols of the rare earth elements 
to be added. 
The magnetic thin film of this invention has the whole or part of the 
region of construction thereof formed of an amorphous region and, owing to 
the amorphousness of the construction, has the magnetic properties thereof 
improved by decreasing the eddy current loss in the high frequency range. 
This effect is further exalted when the magnetic thin film is endowed with 
a hetero-amorphous construction. The region of construction may be 
amorphous either wholly or partly. In order to obtain a process of 
rotational magnetization effectively in a high frequency range, it is 
appropriate that the magnetic thin film should possess uniform uniaxial 
magnetic anisotropy. 
FIG. 1 is a schematic diagram of the construction of a thin film according 
to this invention. FIG. 1 represents one embodiment of this invention and 
is not meant to restrict the shape, surface area ratio, etc. of any of the 
regions of the thin film in any sense. In FIG. 1, 11 represents an 
amorphous region, a crystalline region, or a mixed amorphous-crystalline 
region, each containing Fe, Co, and Sm together and 12 represents a region 
containing B and an element, X, of the Group IVB elements in the IU 
version of the Periodic Table together. Then, the symbol A macroscopically 
indicates the direction of the axis of easy magnetization in connection 
with inplane uniaxial magnetic anisotropy. 
First, as the mother phase of a magnetic material which combines high 
saturation magnetization and soft magnetism, a composition comprising Fe, 
Co, B, and one or more elements, X, selected from among the Group IVB 
elements in the IU version of the Periodic Table is adopted. 
This mother phase assumes a hetero-amorphous phase or a mixed 
amorphous-crystalline phase, depending on the composition and the 
film-forming condition to be suitably selected, and permits induction and 
control of uniaxial magnetic anisotropy and acquires excellent high 
frequency magnetic characteristics in addition to exhibiting high 
saturation magnetization and soft magnetism. 
For the purpose of lowering the value of magnetostriction constant, this 
invention contemplates adding either Sm or rare earth elements containing 
not less than 50% of Sm to this mother phase. 
In the case of an Fe--Co--B--X type hetero-amorphous film or a 
microcrystalline film, the addition of Sm or rare earth elements 
containing not less than 50 mol % of Sm proves effective particularly for 
the sake of lowering positive magnetostriction. 
The reduction of the magnetostriction constant due to the addition of Sm or 
rare earth elements containing not less than 50 mol % of Sm is considered 
to be proportional substantially linearly to the amount of this addition 
to the composition. 
Appropriately the amount of the rare earth elements to be added is not more 
than 10 at % from the viewpoint of lowering the absolute value of the 
magnetostriction constant to below that of the mother phase. Also from the 
viewpoint of repressing the reduction of the spontaneous magnetization, 
the addition of rare earth element in an amount exceeding 10 at % proves 
unfavorable. 
The inventor has been ascertained that the reduction of the positive 
magnetostriction is attained to a certain extent by increasing the amounts 
of Si and Sn as the elements, X, selected from among the Group IVB 
elements in the IU version of the Periodic Table to the mother phase. 
In this case, the increase of the amounts of Si and Sn simultaneously 
entails a hardly ignorable decrease in the spontaneous magnetization and 
proves unfavorable for the magnetic thin film for use in a thin film 
magnetic element. 
In contrast, since the addition of Sm or rare earth elements containing not 
less than 50 mol % of Sm contemplated by this invention is highly 
effective in decreasing the positive magnetostriction, the reduction of 
the spontaneous magnetization which is entailed by the addition of Sm or 
rare earth elements containing not less than 50 mol % of Sm intended to 
lower the magnetostriction as required is repressed to the least allowable 
extent. 
As demonstrated in the working examples to be cited below, the low coercive 
force possessed by the mother phase is not found to be impaired by the 
addition of Sm or rare earth elements containing not less than 50 mol % of 
Sm. 
As respects the local magnetic anisotropy in the region containing Fe and 
Co and supporting magnetism, since the addition of Sm or rare earth 
elements containing not less than 50 mol % of Sm results in decreasing the 
absolute value of the magnetostriction constant, the local magnetic 
anisotropy is considered to be consequently lowered. 
Since the growth of the local magnetic anisotropy degrades the possibility 
of the development of soft magnetism, it is seen that the addition of Sm 
or rare earth elements containing not less than 50 mol % of Sm is 
favorable from the viewpoint of retaining low coercive force and soft 
magnetism. 
So long as Sm is a main component, the effect of the present invention is 
retained when rare earth elements other than Sm is added simultaneously 
with Sm. According to the inventor's knowledge, Sm excels all the other 
elements in terms of effecting the decrease of the magnetostriction. By 
the simultaneous addition of Sm and other rare earth elements, however, 
the cost of the starting material is repressed and the provision of an 
inexpensive magnetic thin film and consequently the provision of an 
inexpensive thin film magnetic element are facilitated. As a concrete 
example of the rare earth element which is highly effective as Sm in 
lowering the magnetostriction, Gd may be cited. 
Specifically, the addition of Sm and other rare earth elements is 
implemented, for example, by preparing a sintered target of mother phase, 
mounting on the target a chip such as of Sm or a chip of an alloy of a 
transition metal with Sm, and then co-sputtering the target and the chip 
or by preparing a target by sintering a material having Sm incorporated in 
a mother phase and sputtering the target. Alternatively, a film aimed at 
may be formed by preparing a composition combining a mother phase with Sm, 
distributing the composition to a multiplicity of targets as divided by 
elements or by suitable alloy compositions, and then subjecting the 
targets to the sputtering operation using a multiplicity of sputtering 
sources or a multiplicity of vacuum evaporation sources, or the 
combinations thereof. For the production of the film, CVD, flame spraying, 
rolling, or plating may be adopted besides the PVD mentioned above. 
Further to the magnetic thin film mentioned above, uniform inplane uniaxial 
magnetic anisotropy is imparted. The time and method for the impartation 
of uniaxial magnetic anisotropy are not particularly limited, though the 
heat treatment performed in a magnetic field is generally suitable for the 
impartation under discussion. The formation of the film in a magnetic 
field during the formation of a magnetic layer, the heat treatment in a 
magnetic field immediately after the formation of a magnetic film, and the 
heat treatment in a magnetic field after the manufacture of a magnetic 
element may be proper methods. Such mechanical methods as the shaping of a 
substrate before the film formation, the introduction of stress to the 
film before or after the formation of the film, and the performance of the 
pattering work by a varying etching technique after the lamination are 
also conceivable. The technique for generating anisotropic stress in a 
controlled manner during the process of manufacturing a thin film magnetic 
element may be otherwise adopted. In consequence of this treatment, the 
excitation along the axis of hard magnetization adequate for high 
frequency excitation can be realized. 
By the method described above, a magnetic thin film which assumes low 
magnetostriction and consequently acquires such magnetic characteristics 
as are sparingly susceptible to the influence of the stress emanating from 
the other components in the magnetic element, enjoys uniaxial magnetic 
anisotropy with excellent controllability, and exhibits characteristics 
such as low loss at high frequency, high saturation magnetization, and 
soft magnetism can be obtained. 
Further, by using the magnetic thin film of this invention as a magnetic 
substance for magnetic elements such as, for example, the thin film 
inductor, magnetic substances possessing the optimum magnetic properties 
required for various magnetic elements and thin film magnetic elements 
possessing excellent electric and magnetic properties can be realized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, specific working examples of this invention will be described below. 
Examples 1-6 and Comparative Examples 1 and 2 
Magnetic thin films of the examples and the comparative examples were 
formed by the use of a magnetron sputtering device under the film-forming 
conditions shown in Table 1 and Table 2. A Si wafer provided with a 
thermally oxidized film was used as the substrate. Immediately before the 
formation of film, the substrate was cleaned by dry etching with Ar gas. 
The film consequently formed was heat-treated in a DC magnetic field in a 
vacuum ambience (DC magnetic field applied: 130 kA/m, temperature of heat 
treatment: not less than 280.degree. C., and duration of the heat 
treatment: 2 to 3 hours). The magnetic field for the heat treatment was 
applied parallelly to the film surface. 
TABLE 1 
______________________________________ 
RF magnetron 
Mode of film formation sputtering 
______________________________________ 
RF power 600 W 
Diameter of target 127 mm.phi. 
Ar gas pressure during film formation 
0.2 Pa 
Distance between target and substrate 
105 mm 
Film thickness about 1.5 .mu.m 
______________________________________ 
TABLE 2 
______________________________________ 
Example 1 
Target Sintered target of a composition of 
Fe: 59.2, Co: 21.4, B: 12.3, C: 7.1 
Sm chip of the square of 2 mm .times. 4 p 
(on target) 
Composition after 
Fe.sub.60.5 Co.sub.22.0 B.sub.11.0 C.sub.5.2 Sm.sub.1.3 
film formation 
Crystal structure 
Hetero-amorphous texture 
after film formation 
Example 2 
Target Sintered target of a composition of 
Fe: 59.2, Co: 21.4, B: 12.3, C: 7.1 
Sm chip of the square of 2 mm .times. 2 p 
(on target) 
Crystal structure 
Hetero-amorphous texture 
after film formation 
Example 3 
Target Sintered target of a composition of 
Fe: 59.2, Co: 21.4, B: 12.3, C: 7.1 
Sm chip of the square of 2 mm .times. 6 p 
(on target) 
Crystal structure 
Hetero-amorphous texture 
after film formation 
Example 4 
Target Sintered target of a composition of 
Fe: 59.2, Co: 21.4, B: 12.3, C: 7.1 
Sm chip of the square of 2 mm .times. 10 
p (on target) 
Crystal structure 
Hetero-amorphous texture 
after film formation 
Example 5 
Target B.sub.4 C chip 20 mm.phi. in diam. .times. 7 p + Sm chip 
of the square of 2 mm .times. 4 p on alloy of 
Fe 75 - Co 25 
Composition Fe.sub.54.5 Co.sub.18.2 B.sub.18.9 C.sub.7.9 Sm.sub.0.5 
after film 
formation 
Crystal Hetero-amorphous texture 
structure after 
film formation 
Example 6 
Target B.sub.4 C chip 20 mm.phi. in diam. .times. 5 p + Sm chip 
of the square of 2 mm .times. 8 p on alloy of 
Fe 75 - Co 25 
Composition Sm 1.2 at % 
after film 
formation 
Crystal Crystalline + Hetero-amorphous texture 
structure after 
film formation 
Comparative Example 1 
Target Sintered target of a composition of Fe: 
59.2, Co: 21.4, B: 12.3, C: 7.1 
Composition Fe.sub.62.7 Co.sub.22.6 B.sub.6.6 C.sub.8.1 
after film 
formation 
Crystal Hetero-amorphous texture 
structure after 
film formation 
Comparative Example 2 
Target B.sub.4 C chip 20 mm.phi. in diam. .times. 7 p. on alloy 
of Fe 75 - Co 25 
Composition Sm 0 at % 
after film 
formation 
Crystal Hetero-amorphous texture 
structure after 
film formation 
______________________________________ 
The film thickness was determined with a contact stylus type surface 
roughness/film thickness meter. The analysis of composition was carried 
out by an inductively coupled plasma-optical emission analytical 
spectrometry and an infrared absorption spectrometry under radio-frequency 
heating. The crystal structure was confirmed by the thin film X-ray 
diffraction method having the angle of incidence fixed at 2.0 degrees. The 
spontaneous magnetization, the coercive force, etc. were rated by the 
measurement of a magnetization curve obtained with a vibrating sample 
magnetometer. 
The magnetostriction was determined visually by the optical lever method 
using an external magnetic field of not more than 80 kA/m, rotated in a 
plane containing both an axis of easy magnetization and an axis of hard 
magnetization. The saturation magnetostriction constant was estimated 
based on the magnetostriction curves obtained by the optical lever method. 
FIG. 2 is a diagram showing the dependency of the saturation 
magnetostriction constant on the Sm composition, obtained of each of the 
samples of Examples 1 to 4 and Comparative Example 1 prepared by using a 
sintered target of the same composition. 
FIG. 3 shows the dependency of the spontaneous magnetization on the Sm 
composition, obtained of each of the samples. 
It is found from FIG. 2 and FIG. 3 that the saturation magnetostriction 
constant and the spontaneous magnetization were both lowered by the 
addition of Sm and that the ratio of decrease of the magnetostriction 
constant was more than 3 times the ratio of decrease of the spontaneous 
magnetization. The data indicate that the enough decrease of the 
saturation magnetostriction constant is obtained while repressing the 
decrease of the spontaneous magnetization to the least possible extent. 
FIG. 4 shows typical results of the determination of the coercive force of 
each of the samples in the direction of the axis of hard magnetization. 
From the results given above, it is found that the retention of fully 
satisfactory soft magnetism fit for the operation in a high frequency 
magnetic field is attained by the addition of Sm. 
Example 5 and Comparative Example 2 are examples of film formation using a 
Fe--Co alloy and various chips and invariably producing hetero-amorphous 
magnetic thin films by the same procedure excepting the presence and the 
absence of Sm. The saturation magnetostriction constant (.lambda.s) 
obtained in Comparative Example 2 was 4.2.times.10.sup.-5 and that in 
Example 5 was 3.8.times.10.sup.-5, indicating that the addition of Sm was 
effective in lowering the magnetostriction constant without reference to 
the method of film formation. 
Example 6 is an example of film formation using a Fe--Co alloy and various 
chips as in Example 5. In the present case, the crystal structure 
consisted of a crystal texture and a hetero-amorphous texture. The 
saturation magnetostriction constant (.lambda.s) obtained in this case was 
2.times.10.sup.-5, clearly indicating that even in the mixed 
crystalline-amorphous phase of the material of this invention, the sample 
incorporating Sm showed low magnetostriction coefficient. 
In Examples 7 and 8 and Comparative Examples 3 and 4, thin film magnetic 
elements were produced from such magnetic thin films as shown above under 
the conditions shown in Table 
TABLE 3 
______________________________________ 
Formation of coil film 
Cu film by plating method 
Method of embedding coil 
Application of polyimide by 
film the use of a spin coater 
Insulation and spacing 
SiO.sub.2 by sputtering and 
between laminated magnetic 
polyimide 
film and coil film 
______________________________________ 
In Example 7, magnetic thin films prepared by the procedure of Example 3 
and insulating layers of AlN (0.4 .mu.m in thickness) were alternately 
superposed in four layers and the resultant superposed layers were 
collectively patterned by etching with a mixed acid. 
In Example 8, magnetic thin films prepared by the procedure of Example 3 
and insulating layers of AlN (0.4 .mu.m in thickness) were alternately 
superposed in four layers and the resultant superposed layers were 
patterned by alternately and sequentially etching the insulating layers 
and the magnetic layers with two kinds of etchant. 
In Comparative Example 3, magnetic thin films prepared by the procedure of 
Comparative Example 1 and insulating layers of AlN (0.4 .mu.m in 
thickness) were alternately superposed in four layers and the resultant 
superposed layers were collectively patterned by etching with a mixed 
acid. 
In Comparative Example 4, magnetic thin films prepared by the procedure of 
Comparative Example 1 and insulating layers of AlN (0.4 .mu.m in 
thickness) were alternately superposed in four layers and the resultant 
superposed layers were patterned by alternately and sequentially etching 
the insulating layers and the magnetic layers with two kinds of etchant. 
A thin film inductor element was obtained in Example 7 by using a laminated 
magnetic thin film having four AlN insulating layers superposed through 
the medium of magnetic thin films produced by the procedure of Example 3. 
The magnetic thin films in the completed inductor element were found to 
have an anisotropic magnetic field which only showed a deviation within 
0.3 kA/m relative to the anisotropic magnetic field of 1.1 kA/m obtained 
originally in Example 3. 
In a thin film inductor element obtained in Comparative Example 3 by 
similarly superposing magnetic thin films prepared by the procedure of 
Comparative Example 1, the magnetic thin films in the completed inductor 
element were found to have an anisotropic magnetic field which showed a 
discernible maximum increase of 2 kA/m relative to the original 
anisotropic magnetic field. 
These examples represent the cases of having the relevant superposed 
magnetic thin films collectively patterned with a mixed solvent. When the 
magnetic layers and the insulating layers in the superposed magnetic thin 
films were patterned by alternately etching them with different etchants, 
the inductor element of Example 8 using magnetic thin films obtained by 
the procedure of Example 3 was found to show no discernible degradation of 
coercive force. Meanwhile, the inductor element of Comparative Example 4 
using magnetic thin films obtained by the procedure of Comparative Example 
1 was found to show a degraded coercive force of about 400 A/m. Thus, the 
latter inductor element failed to acquire ample soft magnetism. Thus, 
Comparative Example 4 failed to obtain a thin film magnetic element 
exhibiting fully satisfactory characteristics. 
FIG. 5A, FIG. 5B, and FIG. 5C illustrate the laminate structure of main 
components of a thin film inductor element using a magnetic thin film of 
this invention. FIG. 5A is a plan view, in which 51 represents a patterned 
magnetic film. FIG. 5B is a plan view of coil part, and FIG. 5C is a cross 
section taken through FIG. 5A along the line 5C--5C, in which 51 
represents a magnetic film, 52 an insulating layer, 53 a coil layer, and 
55 a substrate. 
As is clearly noted from the working examples cited above, this invention 
allows production of a magnetic thin film which exhibits low saturation 
magnetostriction constant, possesses uniaxial magnetic anisotropy, and 
excels in high saturation magnetization and soft magnetism. 
It has been confirmed that, in a thin film magnetic element using this 
magnetic thin film, the magnetic characteristics inherent in the magnetic 
thin film are retained substantially intact. 
In the comparative examples, the magnetic thin films showed high saturation 
magnetostriction constants and, in the thin film magnetic elements using 
these magnetic thin films, the magnetic characteristics of the magnetic 
thin films were varied. Thus, the thin film magnetic elements failed to 
acquire necessary magnetic characteristics. 
As described in detail above, this invention concerns a magnetic film to be 
used in such planar magnetic elements as planar inductors and thin film 
magnetic heads. It provides a magnetic thin film which retains high 
saturation magnetization, soft magnetism, and ability to control inplane 
uniaxial magnetic anisotropy and, at the same time, exhibits a low 
saturation magnetostriction constant, and possesses magnetic 
characteristics not easily degraded by the occurrence of anisotropic 
stress, dispersion of the stress, or the variation thereof during or after 
the process for the manufacture of a planar magnetic element and a planar 
magnetic element using the magnetic thin film.