Magnetoresistive film

Disclosed is a magnetoresistive film which includes an antiferromagnetic layer, a first amorphous ferromagnetic layer, a crystalline ferromagnetic interlayer disposed between the antiferromagnetic layer and the first amorphous ferromagnetic layer, a nonmagnetic conductive layer provided on the first amorphous ferromagnetic layer and a ferromagnetic layer provided on the nonmagnetic conductive layer.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to magnetoresistive films for use in 
reproduce magnetic heads, magnetic sensors or the like. 
2. Description of Related Art 
A magnetoresistive (MR) element is an element which detects an intensity of 
magnetic field and its changes by supplying a current to a 
magnetoresistive film and reading the voltage changes thereacross. An MR 
head employing such a magnetoresistive element offers a higher detectivity 
relative to conventional inductive heads, and accordingly increased 
investigations upon the MR head have been directed to its applications to 
reproduce magnetic heads such as hard disk drives which demand higher 
density recording. In order for such a MR head to be feasible in achieving 
high density recording, it must have a high magnetic field sensitivity As 
a result, a significant need has arisen for a MR element which exhibits a 
high MR ratio. A giant magnetoresistive (GMR) element is known as 
exhibiting such a high MR ratio. Examples of magnetic films for such a GMR 
element include artificial lattice type magnetic films having 
ferromagnetic layers alternating with nonmagnetic conductive layers, spin 
valve type magnetic films having a layered structure consisting of 
antiferromagnetic/ferromagnetic/nonmagnetic conductive/ferromagnetic 
layers, coercive force differential type magnetic films having a 
multilayer structure consisting of ferromagnetic/nonmagnetic 
conductive/ferromagnetic layers with the ferromagnetic layers having 
coercive forces different from each other. 
A magnetic film for the GMR elements has been proposed by M. Jimbo et 
al.(J. Appl. Phys., 79 (1966) 6237-6239) which employs an amorphous 
ferromagnetic layer for the ferromagnetic layer and has a multilayer 
structure of NiO/a-CoFeB/Cu/a-CoFeB. 
However, the MR films employing such an amorphous ferromagnetic layer 
suffer poor reproducibility in their formation to disadvantageously 
exhibit varied qualities from film to film. In addition, they exhibit a 
lower MR ratio than MR films employing a crystalline ferromagnetic layer. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a magnetoresistive film 
employing an amorphous ferromagnetic layer which exhibits a high MR ratio 
and can be manufactured in such a reproducible manner as to insure uniform 
qualities thereof. 
The inventors of the present application have conceivably related the poor 
reproducibility of the RM films employing the amorphous ferromagnetic 
layer to a weak magnetic coupling between the antiferromagnetic layer and 
amorphous ferromagnetic layer. That is, such a weak magnetic coupling have 
been considered to be readily susceptible to the changes in the film 
structure due to a slight variation in a film-forming condition to result 
in the poor reproducibility of the film formation as well as the reduced 
RM ratio. Therefore, there is a need to find a way of eliminating the 
above-described problems. The present inventors have now discovered that 
the placement of crystalline ferromagnetic interlayer between the 
amorphous ferromagnetic and antiferromagnetic layers results in an 
enhanced magnetic coupling of the amorphous ferromagnetic layer to the 
antiferromagnetic layer. 
A characteristic feature of the present invention resides in its multilayer 
structure including antiferromagnetic, first amorphous ferromagnetic, 
nonmagnetic conductive, and ferromagnetic layers in such an order and 
further placement of a crystalline ferromagnetic interlayer between the 
first amorphous ferromagnetic and antiferromagnetic layers. 
More specifically, the magnetoresistive film of the present invention 
includes the antiferromagnetic layer, the crystalline ferromagnetic 
interlayer, the first amorphous ferromagnetic layer, the nonmagnetic 
conductive layer, and the ferromagnetic layer in such an order. The 
crystalline ferromagnetic interlayer is ferromagnetically coupled to the 
first amorphous ferromagnetic layer, so that the ferromagnetically coupled 
crystalline ferromagnetic interlayer and first amorphous ferromagnetic 
layer are magnetically coupled to the antiferromagnetic layer. 
The provision of the crystalline ferromagnetic interlayer between the 
antiferromagnetic and first amorphous ferromagnetic layers in accordance 
with the present invention allows the antiferromagnetic layer to be 
strongly exchange coupled to the crystalline ferromagnetic interlayer and 
the first amorphous ferromagnetic layer. This imparts thereto an enhanced 
pinch effect of the first amorphous ferromagnetic layer to result in an 
increased MR ratio. Also, since the antiferromagnetic layer is strongly 
magnetically coupled to the crystalline ferromagnetic interlayer and first 
amorphous ferromagnetic layer, the magnetoresistive film is little 
susceptible to the variations in film-forming condition so that it can be 
fabricated in such a reproducible manner to insure uniformity in quality 
level of the resulting films. 
The crystalline ferromagnetic interlayer in accordance with the present 
invention may be comprised of Fe, Co, Ni and alloys thereof, for example. 
Of the above, NiFe, NiCo, CoFe, NiFeCo are particularly preferred. The 
thickness of the crystalline ferromagnetic interlayer is not particularly 
limited, but is generally in the range of 5-50 .ANG.. 
In the present invention, at least one of the ferromagnetic layers for 
flanking the nonmagnetic conductive layer therebetween is specified to be 
the amorphous ferromagnetic layer. Accordingly, in a particular 
embodiment, first and second amorphous ferromagnetic layers may be 
employed to flank the nonmagnetic conductive layer therebetween. 
Suitable materials for the amorphous ferromagnetic layer in accordance with 
the present invention include CoFeB, CoNb, CoZr, CoZrNb, CoTa, CoTaZr, 
CoNbTa, CoB, CoFeZr, CoFeTa, CoFeNb, CoNiB, CoNiZr, CoNiTa and CoNiNb, for 
example. These alloys may additionally contain a small amount of metal 
such as Cr. The thickness of the amorphous ferromagnetic layer is 
generally in the range of 5-100 .ANG.. 
One of the ferromagnetic layers for flanking the nonmagnetic conductive 
layer may not be amorphous. Even in such an event, the thickness of such a 
ferromagnetic layer may be set generally in the range of 5-100 .ANG.. 
Apart from the amorphous ferromagnetic layer, the crystalline 
ferromagnetic layer may consist of NiFe, Fe, Co or alloys thereof, for 
example. 
The antiferromagnetic layer for use in the present invention may consist of 
FeMn, NiMn, IrMn, NiO, CoO or NiCoO, for example. The thickness of the 
antiferromagnetic layer is generally in the range of 30-300 .ANG.. 
Any material which is nonmagnetic and excellent in electric conductivity 
can be employed for the nonmagnetic conductive layer in accordance with 
the present invention. Representative of such materials are Cu and Ag. The 
thickness of the nonmagnetic conductive layer is generally in the range of 
10-50 .ANG.. 
The magnetoresistive film of the present invention can be fabricated by 
sequentially forming the layers on a substrate. In this instance, the 
layers may be formed on the substrate in the order of the 
antiferromagnetic, crystalline ferromagnetic, first amorphous 
ferromagnetic, nonmagnetic conductive and ferromagnetic layers. 
Alternatively, such an order may be inverted. That is, the layers may be 
formed on the substrate in the order of the ferromagnetic layer, the 
nonmagnetic conductive layer, the first amorphous ferromagnetic layer, the 
crystalline ferromagnetic interlayer and the antiferromagnetic layer. The 
substrate may be made of any suitable nonmagnetic material such as Si, 
TiC, Al.sub.2 O.sub.3 or glass, for example. 
Also, the magnetoresistive film of the present invention may have a 
multilayer structure in which the layered sequence of the above-described 
five-layer structure is repeated two or more times. 
In accordance with the present invention, the crystalline ferromagnetic 
interlayer is provided between the antiferromagnetic and first amorphous 
ferromagnetic layers. The provision of the crystalline ferromagnetic 
interlayer allows the first amorphous ferromagnetic layer to be 
ferromagnetically coupled thereto, so that these ferromagnetically coupled 
layers are magnetically coupled to the antiferromagnetic layer. Although 
not intended to limit the scope of the invention, it is believed that the 
relatively strong ferromagnetic coupling between the crystalline 
ferromagnetic interlayer and the first amorphous ferromagnetic layer as 
well as the relatively strong magnetic coupling between the 
antiferromagnetic layer and those two layers allow the magnetization 
mechanism of magnetoresistive film to shift from a conventional type 
similar to that of the coercive force differential type magnetic film to a 
more stable spin valve type, resulting in its reproducible high MR ratio.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a cross-sectional view of a first embodiment of the 
magnetoresistive film in accordance with the present invention. With 
reference to FIG. 1, a magnetoresistive film in accordance with this 
embodiment can be established by sequentially forming on a substrate 1 
such as of glass an antiferromagnetic layer 2 of Ni.sub.50 O.sub.50 (10 nm 
thick), a crystalline ferromagnetic interlayer 3 of Ni.sub.80 Fe.sub.20 (2 
nm thick), a first amorphous ferromagnetic layer 4 of (Co.sub.0.9 
Fe.sub.0.1).sub.20 B.sub.80 (2 nm thick), a nonmagnetic conductive layer 5 
of Cu (2 nm thick), and a second amorphous ferromagnetic layer 6 of 
(Co.sub.0.9 Fe.sub.0.1).sub.20 B.sub.80 (2 nm thick). 
FIGS. 2 and 3 are schematic cross-sectional views, respectively, showing a 
process for fabricating the magnetoresistive film embodiment of FIG. 1. As 
illustrated in FIG. 2(a), the antiferromagnetic layer 2 is formed on the 
glass substrate 1 such as by an ion beam sputtering technique. The 
crystalline ferromagnetic interlayer 3 is then formed on the 
antiferromagnetic layer 2 such as by the ion beam sputtering technique, as 
illustrated in FIG. 2(b). As shown in FIG. 2(c), the first amorphous 
ferromagnetic layer 4 is subsequently formed on the crystalline 
ferromagnetic interlayer 3 such as by the ion beam sputtering technique. 
Then, the nonmagnetic conductive layer 5 is formed on the first amorphous 
ferromagnetic layer 4 such as by an ion beam sputtering technique. 
Finally, the second amorphous ferromagnetic layer 6 is formed on the 
nonmagnetic conductive layer 5 such as by the ion beam sputtering 
technique. 
The magnetoresistive film can be thus fabricated which has a multilayer 
structure as shown in FIG. 1. Although each layer is described above to be 
formed by the ion beam sputtering technique, other techniques including a 
RF plasma CVD process can be employed to form any of the layers. 
FIG. 4 is a graph showing variations of MR ratio according to magnetic 
field changes of the first embodiment, shown in FIG. 1, of the 
magnetoresistive film in accordance with the present invention. In FIG. 4, 
a curve (1) shows the changes in MR ratio of the first embodiment, shown 
in FIG. 1, of the magnetoresistive film in accordance with the present 
invention, and a curve (2) shows the changes in MR ratio of the 
comparative magnetoresistive film. The crystalline ferromagnetic 
interlayer is not incorporated in the comparative magnetoresistive film 
which accordingly forms the first amorphous ferromagnetic layer directly 
on the antiferromagnetic layer. That is, the comparative magnetoresistive 
film is such a magnetoresistive film that excludes the crystalline 
ferromagnetic interlayer 3 from the magnetoresistive film of FIG. 1 and 
forms the first amorphous ferromagnetic layer 4 directly on the 
antiferromagnetic layer. 
As apparent from FIG. 4, the first embodiment of the magnetoresistive film 
in accordance with the present invention reveals a value of about 8% for a 
maximum MR ratio. Its maximum MR ratio is apparently higher than a 4% 
maximum MR ratio of the comparative magnetoresistive film which 
incorporates no crystalline ferromagnetic interlayer between the 
antiferromagnetic and first amorphous ferromagnetic layers. 
The first embodiment of the magnetoresistive film in accordance with the 
present invention was repeatedly fabricated to prepare seven samples 
(Sample 1 through Sample 7). FIG. 5 shows a plot of the maximum MR ratio 
for each sample. For comparative purposes, the comparative 
magnetoresistive film which incorporated no crystalline ferromagnetic 
layer to exhibit the MR ratio curve (2) in FIG. 4 was repeatedly 
fabricated to prepare seven samples (Sample 1 through Sample 7). FIG. 5 
also shows a plot of the maximum MR ratio for each sample of the 
comparative magnetoresistive film. As apparent from FIG. 5, the 
comparative magnetoresistive film incorporating no crystalline 
ferromagnetic layer exhibits larger sample variances in maximum MR ratio. 
In contrast, the first embodiment of the magnetoresistive film in 
accordance with the present invention exhibits rather smaller sample 
variances in maximum MR ratio, i.e. a substantially constant MR ratio. 
This demonstrates that the magnetoresistive film in accordance with the 
present invention can be fabricated in such a reproducible manner to keep 
its quality level. 
FIG. 6 is a graph showing variations in MR ratio with magnetic field 
changes of a second embodiment of the magnetoresistive film in accordance 
with the present invention. In the second embodiment of the 
magnetoresistive film in accordance with the present invention, a 
crystalline ferromagnetic interlayer of Ni.sub.14 Fe.sub.13 Co.sub.73 (2 
nm thick) is used as the crystalline ferromagnetic interlayer 3 shown in 
FIG. 1. Excluding the crystalline ferromagnetic interlayer 3, the material 
type and thickness of each layer of the film was identical to the 
corresponding layer of the above-described first film embodiment. In FIG. 
6, a curve (1) shows variations in MR ratio of the second embodiment of 
the magnetoresistive film. A curve (2) in FIG. 6 shows variations in MR 
ratio of the comparative magnetoresistive film incorporating no 
crystalline ferromagnetic layer, as analogous to the curve (2) in FIG. 4. 
As can be seen from FIG. 6, the second embodiment of the magnetoresistive 
film in accordance with the present invention reveals a value of about 8% 
for a maximum MR ratio which is apparently higher than those of 
conventional films. 
The second embodiment of the magnetoresistive film in accordance with the 
present invention was repeatedly fabricated to prepare seven samples 
(Sample 1 through Sample 7). FIG. 7 shows a plot of the maximum MR ratio 
for each sample to indicate sample variances in MR ratio. For comparative 
purposes, the comparative magnetoresistive film which incorporated no 
crystalline ferromagnetic layer to exhibit the MR ratio curve (2) in FIG. 
6 was repeatedly fabricated to prepare seven samples (Sample 1 through 
Sample 7). FIG. 7 also shows a plot of the maximum MR ratio for each 
sample of the comparative magnetoresistive film to indicate sample 
variances in MR ratio. As apparent from FIG. 7, the second embodiment of 
the magnetoresistive film in accordance with the present invention 
exhibits rather smaller sample variances in maximum MR ratio. This 
demonstrates that the second embodiment of the magnetoresistive film can 
be fabricated in such a reproducible manner to keep its quality level. 
In the above embodiments, formed on the substrate 1 is the 
antiferromagnetic layer 2 on which the remaining layers are sequentially 
formed. Alternatively, the sequence of the layers to be formed may be 
inverted. That is, those layers may be formed on the substrate 1 in the 
order of second amorphous ferromagnetic layer 6, nonmagnetic conductive 
layer 5, first amorphous ferromagnetic layer 4, crystalline ferromagnetic 
interlayer 3 and antiferromagnetic layer 2. 
Next, the investigation was made as to the influence imposed by variations 
in thickness of the amorphous ferromagnetic layer in the magnetoresistive 
film of the present invention. As illustrated in FIG. 8, sequentially 
formed on a NiO antiferromagnetic layer 11 (100 .ANG.) are a NiFe 
crystalline ferromagnetic layer 12 (20 .ANG.), a first CoFeB amorphous 
ferromagnetic layer 13, a Cu nonmagnetic conductive layer 14 (20 .ANG.) 
and a second CoFeB amorphous ferromagnetic layer 15. While the thicknesses 
of NiO antiferromagnetic layer 11, NiFe crystalline ferromagnetic layer 12 
and Cu nonmagnetic conductive layer 14 were respectively maintained 
constant, the thicknesses of CoFeB amorphous ferromagnetic layers 13 and 
15 were varied as shown in FIGS. 10 and 11 to measure the changes in MR 
ratio (FIG. 10) and the changes in operating magnetic field (Hp) (FIG. 11) 
in accordance therewith. For comparative purposes, the investigation was 
also made as to the influence imposed by variations in thickness of a 
ferromagnetic layer in a conventional magnetoresistive film of FIG. 9. As 
illustrated in FIG. 9, such a comparative magnetoresistive film has a FeMn 
antiferromagnetic layer 21 (100 .ANG.) on which a Co ferromagnetic layer 
22 a Cu nonmagnetic conductive layer 23 (20 .ANG.) and a Co ferromagnetic 
layer 24 are sequentially formed. While the thicknesses of FeMn 
antiferromagnetic layer 21 and Cu nonmagnetic conductive layer 23 were 
respectively maintained constant, the thicknesses of Co ferromagnetic 
layers 22 and 24 were varied to measure the changes in MR ratio (FIG. 10) 
and the changes in operating magnetic field (Hp) (FIG. 11) in accordance 
therewith. 
FIG. 12 is a graph explaining the operating magnetic field (Hp). Referring 
to FIG. 12, the operating magnetic field (Hp) is indicated as 
corresponding to a magnetic field width wherein the MR ratio changes 
linearly. Accordingly, a higher magnetic sensitivity can be obtained as 
the operating magnetic field (Hp) becomes narrower. 
As can be seen from FIG. 10, the magnetoresistive film (CoFeB) in 
accordance with the present invention exhibits a substantially constant, 
high MR ratio even when the thickness of its amorphous ferromagnetic layer 
is varied within the range of 5-50 .ANG.. On the contrary, it is shown 
that the comparative magnetoresistive film (Co) exhibits reduction in MR 
ratio as the ferromagnetic layer becomes thinner. 
In addition, the magnetoresistive film (CoFeB) in accordance with the 
present invention exhibits a substantially constant, low operating 
magnetic field even when the thickness of its amorphous ferromagnetic 
layer is varied within the range of 5-50 .ANG., as can be appreciated from 
FIG. 11. On the contrary, it is shown that the comparative 
magnetoresistive film (Co) exhibits an increase in operating magnetic 
field intensity to result in its poorer magnetic field sensitivity as the 
ferromagnetic layer therein becomes thicker. As will be recognized from 
FIGS. 10 and 11 it is a marked disadvantage of the comparative 
magnetoresistive film that the increased thickness of its ferromagnetic 
layer in an attempt to obtain a higher MR ratio adversely acts to reduce 
the operating magnetic field sensitivity. On the other hand, the 
magnetoresistive film in accordance with the present invention is little 
influenced by the changes in thickness of the ferromagnetic layer to 
constantly exhibit a high MR ratio as well as an is adequate magnetic 
field sensitivity. 
FIG. 13 is a cross-sectional view of a third embodiment of the 
magnetoresistive film in accordance with the present invention. In the 
embodiment as illustrated in FIG. 13, a magnetoresistive film has a 
multilayer structure wherein layers are formed on a substrate 31 in the 
order of antiferromagnetic layer 32, crystalline ferromagnetic interlayer 
33, first amorphous ferromagnetic layer 34, nonmagnetic conductive layer 
35, second amorphous ferromagnetic layer 36, nonmagnetic conductive layer 
37, first amorphous ferromagnetic layer 38, crystalline ferromagnetic 
interlayer 39 and antiferromagnetic layer 40. The antiferromagnetic layer 
32 is formed of Ni.sub.50 O.sub.50 to a thickness of 10 nm, for example. 
The crystalline ferromagnetic interlayers 33 and 39 are formed of 
Ni.sub.80 Fe.sub.20 or Ni.sub.14 Fe.sub.13 Co.sub.73 to a thickness of 2 
nm, for example. The first and second amorphous ferromagnetic layers 34, 
36 and 38 are formed of (Co.sub.0.9 Fe.sub.0.1).sub.20 B.sub.80 to a 
thickness of 2 nm, for example. The nonmagnetic conductive layers 35 and 
37 are formed of Cu to a thickness of 2 nm, for example. 
FIG. 14 is a cross-sectional view of a fourth embodiment of the 
magnetoresistive film in accordance with the present invention. In the 
embodiment as illustrated in FIG. 14, a magnetoresistive film has a 
multilayer structure wherein layers are formed on a substrate 41 in the 
order of second amorphous ferromagnetic layer 42, nonmagnetic conductive 
layer 43, first amorphous ferromagnetic layer 44, crystalline 
ferromagnetic interlayer 45, antiferromagnetic layer 46, crystalline 
ferromagnetic interlayer 47, first amorphous ferromagnetic layer 48, 
nonmagnetic conductive layer 49 and second amorphous ferromagnetic layer 
50. 
The first and second amorphous ferromagnetic layers 42, 44, 48 and 50 are 
formed of (Co.sub.0.9 Fe.sub.0.1).sub.20 B.sub.80 to a thickness of 2 nm, 
for example. The nonmagnetic conductive layers 43 and 49 are formed of Cu 
to a thickness of 2 nm, for example. The crystalline ferromagnetic 
interlayers 45 and 47 are formed of Ni.sub.80 Fe.sub.20 or Ni.sub.14 
Fe.sub.13 Co.sub.73 to a thickness of 2 nm, for example. The 
antiferromagnetic layer 46 is formed of Ni.sub.50 O.sub.50 to a thickness 
of 10 nm, for example. 
Also, the magnetoresistive film of the present invention may be of a 
multilayer structure in which the layered sequence of the above-specified 
five-layer structure is twice repeated, such as comprising 
antiferromagnetic/crystalline ferromagnetic inter-/first amorphous 
ferromagnetic/nonmagnetic conductive/ferromagnetic/nonmagnetic 
conductive/first amorphous ferromagnetic/crystalline ferromagnetic 
inter-/antiferromagnetic layers. Furthermore, the magnetoresistive film of 
the present invention may be of a multilayer structure in which the 
layered sequence of the above-specified five-layer structure is thrice 
repeated, such as comprising antiferromagnetic/crystalline ferromagnetic 
inter-/first amorphous ferromagnetic/nonmagnetic 
conductive/ferromagnetic/nonmagnetic conductive/first amorphous 
ferromagnetic/crystalline ferromagnetic 
inter-/antiferromagnetic/crystalline ferromagnetic inter-/first amorphous 
ferromagnetic/nonmagnetic conductive/ferromagnetic layers. 
As described above, the magnetoresistive film of the present invention may 
be of multilayer structure in which the layered sequence of the 
above-specified five-layer structure is two or more times repeated. 
FIG. 15 is a schematic perspective view showing an exemplary structure of a 
magnetoresistive element employing the magnetoresistive film of the 
present invention. Referring to FIG. 15, a multilayer magnetoresistive 
film 51 is laterally interposed between a pair of longitudinally biased 
layers 54 and 55 such as of CoCrPt, on which respective lead electrodes 52 
and 53 such as of Au are provided. As indicated by an arrow A, a current 
supplied from the lead electrode 52 flows through the longitudinally 
biased layer 54, the magnetoresistive film 51 and the longitudinally 
biased layer 55 into the lead electrode 53. In addition to supplying the 
current from the lead electrode 52, the magnetoresistive element is 
designed to read changes in voltage across the magnetoresistive film 51 
for detection of magnetic field intensity and variations thereof. 
FIG. 16 is a cross-sectional view of a fifth embodiment of the 
magnetoresistive film in accordance with the present invention. In this 
embodiment, various materials were employed respectively for the 
crystalline ferromagnetic interlayer and the first amorphous ferromagnetic 
layer to measure variations in exchange coupling magnetic field Hua 
between the antiferromagnetic layer, and the crystalline ferromagnetic 
interlayer and the first amorphous ferromagnetic layer. Referring to FIG. 
16, a magnetoresistive film includes a second amorphous ferromagnetic 
layer 61 of material X1 (3.0 nm thick) on which a nonmagnetic conductive 
layer 62 of Cu (2.6 nm thick) is placed. The nonmagnetic conductive layer 
62 carries thereon a first amorphous ferromagnetic layer 63 of material X2 
(3.0 nm thick) on which a crystalline ferromagnetic interlayer 64 of 
material Y (t nm thick) is mounted. Provided on the crystalline 
ferromagnetic interlayer 64 is an antiferromagnetic layer 65 of FeMn (10.0 
nm thick). 
FIG. 17 shows magnetic field-magnetization curves for the fifth embodiment 
of the magnetoresistive film wherein Co.sub.95 Zr.sub.5 were used as the 
materials X1 and X2 for respectively constituting the second amorphous 
ferromagnetic layer 61 and the first amorphous ferromagnetic layer 63, and 
Ni.sub.80 Fe.sub.20 was used as the material Y for constituting the 
crystalline ferromagnetic interlayer 64, and the thickness t of the 
crystalline ferromagnetic interlayer 64 was set to 3.0 nm. FIG. 17 also 
shows magnetic field-magnetization curves for a comparative 
magnetoresistive film wherein the thickness t of the crystalline 
ferromagnetic interlayer 64 was set to 0 nm, i.e. excluding the 
crystalline ferromagnetic interlayer 64, for comparative purposes. In FIG. 
17, a range represented by "X1" indicates a hysteresis due to changes in 
magnetic moment of the second amorphous ferromagnetic layer 61, and a 
range represented by "X2/Y/FeMn" indicates a hysteresis due to changes in 
magnetic moment of the first amorphous ferromagnetic layer 63, the 
crystalline ferromagnetic interlayer 64 and the antiferromagnetic layer 65 
which are exchange coupled to each other. As can be seen from FIG. 17, 
setting the thickness of crystalline ferromagnetic layer 64 to 3.0 nm 
allows the antiferromagnetic layer 65 to be exchange coupled to the 
crystalline ferromagnetic interlayer 64 and the first amorphous 
ferromagnetic layer 63 to thereby produce the exchange coupling magnetic 
field Hua. 
Next, various materials were selected for the first and second amorphous 
ferromagnetic layers and crystalline ferromagnetic interlayer to prepare 
magnetoresistive films. The magnetoresistive films thus obtained were 
measured for exchange coupling magnetic field Hua. Firstly, measurements 
of exchange coupling magnetic field Hua for a magnetoresistive film were 
made which employed a material a-CoX for the first and second amorphous 
ferromagnetic layers and a material Y for the crystalline ferromagnetic 
interlayer. The results, as well as the types of the materials a-CoX and Y 
employed, are shown in the following Table 1. 
TABLE 1 
______________________________________ 
a-CoX/Y 
X Y Hua(Oe) 
______________________________________ 
B Ni.sub.80 Fe.sub.20 
125 
Zr Ni.sub.80 Fe.sub.20 
115 
Ta Ni.sub.80 Fe.sub.20 
115 
Nb Ni.sub.80 Fe.sub.20 
135 
B Ni.sub.20 Co.sub.80 
125 
Zr Ni.sub.20 Co.sub.80 
120 
Ta Ni.sub.20 Co.sub.80 
120 
Nb Ni.sub.20 Co.sub.80 
125 
B Co.sub.20 Fe.sub.80 
130 
Zr Co.sub.20 Fe.sub.80 
115 
Ta Co.sub.20 Fe.sub.80 
125 
Nb Co.sub.20 Fe.sub.80 
120 
______________________________________ 
In the above Table 1, the X content was in the range of 2-20 atomic 
percent. 
Secondly, magnetoresistive films were prepared which employed a material 
a-(Co.sub.0.9 Ni.sub.0.1)X for the first and second amorphous 
ferromagnetic layers and a material Y for the crystalline ferromagnetic 
interlayer and measured for exchange coupling magnetic field Hua. The 
results, as well as the types of the materials a-(Co.sub.0.9 Ni.sub.0.1)X 
and Y, are shown in the following Table 2. 
TABLE 2 
______________________________________ 
a-(Co.sub.0.9 Ni.sub.0.1)X/Y 
X Y Hua(Oe) 
______________________________________ 
B Ni.sub.80 Fe.sub.20 
130 
Zr Ni.sub.80 Fe.sub.20 
115 
Ta Ni.sub.80 Fe.sub.20 
125 
Nb Ni.sub.80 Fe.sub.20 
120 
B Ni.sub.20 Co.sub.80 
125 
Zr Ni.sub.20 Co.sub.80 
115 
Ta Ni.sub.20 Co.sub.80 
115 
Nb Ni.sub.20 Co.sub.80 
135 
B Co.sub.20 Fe.sub.80 
125 
Zr Co.sub.20 Fe.sub.80 
120 
Ta Co.sub.20 Fe.sub.80 
120 
Nb Co.sub.20 Fe.sub.80 
125 
______________________________________ 
In the above Table 2, the X content was in the range of 2-20 atomic 
percent. 
Thirdly, magnetoresistive films were prepared which employed a material 
a-(Co.sub.0.9 Fe.sub.0.1)X for the first and second amorphous 
ferromagnetic layers and a material Y for the crystalline ferromagnetic 
interlayer and measured for exchange coupling magnetic field Hua. The 
results, as well as the types of the materials a-(Co.sub.0.9 Fe.sub.0.1)X 
and Y, are shown in the following Table 3. 
TABLE 3 
______________________________________ 
a-(Co.sub.0.9 Fe.sub.0.1)X/Y 
X Y Hua(Oe) 
______________________________________ 
B Ni.sub.80 Fe.sub.20 
125 
Zr Ni.sub.80 Fe.sub.20 
120 
Ta Ni.sub.80 Fe.sub.20 
120 
Nb Ni.sub.80 Fe.sub.20 
125 
B Ni.sub.20 Co.sub.80 
130 
Zr Ni.sub.20 Co.sub.80 
115 
Ta Ni.sub.20 Co.sub.80 
125 
Nb Ni.sub.20 Co.sub.80 
120 
B Co.sub.20 Fe.sub.80 
125 
Zr Co.sub.20 Fe.sub.80 
115 
Ta Co.sub.20 Fe.sub.80 
115 
Nb Co.sub.20 Fe.sub.80 
135 
______________________________________ 
In the above Table 3, the X content was in the range of 2-20 atomic 
percent. 
Also, investigations were made as to the thickness of the crystalline 
ferromagnetic interlayer sufficient to produce the exchange coupling 
magnetic field Hua, for the magnetoresistive films consisting of various 
material combinations listed in Tables 1, 2 and 3. It has been found from 
the investigations that setting the thickness of the crystalline 
ferromagnetic interlayer to not lower than 1 nm is effective in enhancing 
the exchange coupling magnetic field Hua. 
As will be appreciated from Tables 1, 2 and 3, any material which consists 
principally of Co can be employed for the amorphous ferromagnetic layer in 
accordance with the present invention. Also, any material can be employed 
for the crystalline ferromagnetic interlayer, so long as it is crystalline 
and ferromagnetic. 
Although at least one of the ferromagnetic layers for flanking the 
nonmagnetic conductive layer therebetween was described as comprising 
amorphous ferromagnetic materials in the above-described embodiments, the 
present invention is not intended to limit the other ferromagnetic 
layer(s), if present, to such amorphous ferromagnetic materials. Excluding 
the ferromagnetic layers adjacent to the crystalline ferromagnetic layer, 
the other ferromagnetic layer(s), if present, may be comprised of suitable 
crystalline ferromagnetic materials. 
It should be understood that the material type and thickness of each layer 
in the magnetoresistive film of the present invention are not limited to 
those described in conjunction with the above embodiments. 
The magnetoresistive film in accordance with the present invention exhibits 
a high MR ratio and can be fabricated in such a reproducible manner to 
maintain its quality level. Accordingly, the magnetoresistive film of the 
present invention can find its utilities in reproduce magnetic heads, 
magnetic sensors and the like.