No-field, low power FeMn deposition giving high exchange films

A method of producing a magnetoresistive read transducer with improved longitudinal bias due to high exchange coupling is disclosed. A layer of antiferromagnetic material is sputtered deposited onto a layer of ferromagnetic material in the absence of a magnetic field and at a power density below 0.7 W/cm.sup.2. The layers of ferromagnetic material and antiferromagnetic material are annealed at a low temperature of between 200.degree. C. and 250.degree. C. for between 6 and 26 hours.

BACKGROUND OF THE INVENTION 
The invention relates to magnetic transducers for reading information 
signals from a magnetic medium. In particular, the invention relates to an 
improved method of depositing magnetoresistive heads which include a layer 
of antiferromagnetic material suitable for exchange stabilization of the 
magnetoresistive sensor. 
Magnetoresistive (MR) heads with magnetoresistive elements (MREs) or 
sensors are known magnetic transducers which are capable of reading data 
from the surface of a magnetic media at higher densities than inductive 
sensor heads. MR sensors detect flux changes in a magnetic media as 
resistance changes in the sensor. The MR sensor is made from a 
ferromagnetic magnetoresistive material which exhibits resistance changes 
as a function of the amount and direction of magnetic flux being sensed by 
the element. 
Permalloy (with a composition near 80 Ni 20 Fe, but abbreviated as NiFe) is 
frequently used as material for MR sensors because of its high magnetic 
permeability and good magnetoresistive response (known as .DELTA.p). When 
an NiFe MR sensor is exposed to external magnetic fields, it can be 
transformed from a single-domain sensor into multi-domain sensor. 
Transformation of the NiFe MR sensor from single domain into multi-domain 
is undesirable because of the resulting lack of stability and loss of 
output amplitude from the sensor. 
One method Of maintaining NiFe MR sensors in a single domain state is known 
as exchange field stabilization. Exchange field stabilization of MR heads 
involves the use of an anti-ferromagnetic thin film material, such as 50 
Fe 50 Mn, to stabilize the NiFe MR sensor. A great deal of research has 
been done on the use of materials such as FeMn to stabilize NiFe MR 
sensors. In exchange field stabilization, one of the magnetic lattices of 
the antiferromagnetic film couples to the magnetic lattice of the NiFe 
film. Since the FeMn film is not susceptible to stray fields, this 
coupling between the antiferromagnetic film and the NiFe film preserves 
the domain state of the MR sensor from the influence of the stray field. 
Prior research and publications in the art concerning the use of FeMn to 
achieve high exchange coupling for exchange stabilization of MR heads have 
disclosed methods of producing MR heads which present a number of 
manufacturing difficulties. For instance, the prior art publications 
report that after depositing the NiFe and FeMn films, the films must be 
annealed at temperatures as high as 270.degree. C. for time periods as 
long as several days in order to achieve high exchange fields. Annealing 
at these high temperatures and for these extended periods of time is not 
practical for manufacturing large quantities of MR heads. Many of these 
prior art methods require multiple anneal cycles which is time consuming 
and undesirable in a manufacturing environment. Also, known fabrication 
techniques use power densities as high as 2.6 W/cm.sup.2 to sputter 
deposit the films, which can cause substantial interdiffusion of the films 
at their interface. Additionally, in order to create an NiFe MR sensor 
with the proper magnetic domain orientation, prior art manufacturing 
methods normally require that the NiFe film be sputter deposited in the 
presence of an applied external magnetic field using permanent magnets 
attached to the pallet near the wafer. However, if the FeMn film is 
sequentially sputter deposited without breaking vacuum, the external 
applied magnetic field makes it difficult to maintain thickness 
uniformities of more than .+-.10 percent which, in some MR head designs, 
is critical. 
One attempt to improve the manufacturability of MR heads while maintaining 
adequate exchange fields is disclosed in U.S. Pat. No. 5,262,914 which 
issued Nov. 16, 1993 to Chen et al. Chen et al. discloses a method of 
producing an MR sensor with a claimed reduction of innealing temperatures 
and times to 240.degree. C. and seven hours, respectively. However, the 
method of producing MR heads with enhanced exchange field of Chen et al. 
requires the addition of a thin layer of interdiffusion material such as 
Au in contact with the layer of FeMn. This addition of an extra thin film 
layer causes an undesirable increase in manufacturing complexity, as well 
as other design related problems. For instance, many MR head designs use 
Au, for example, as contacts for the MR head. In Chen et al., in order to 
allow the Au to diffuse into the FeMn, films such as Ta and Mo which act 
as adhesion promoters and diffusion barriers must be removed. Requiring 
diffusion of Au into FeMn, while preventing it from entering NiFe, 
increases manufacturing complexity. Also, in most MR head designs, the 
layer or layers of Fe Mn are kept as thin as possible in order to reduce 
the height of the device. Frequently, the layer of FeMn will be around 150 
Angstroms. With such a thin layer of FeMn, the Au or other interdiffusion 
material is capable of diffusing through the layer of FeMn and into the 
NiFe sensor, possibly adversely affecting the NiFe sensor's performance. 
SUMMARY OF THE INVENTION 
The present invention provides numerous manufacturing advantages and is 
based upon the recognition that there is a method of producing a 
magnetoresistive read transducer with high exchange field stabilization 
which allows the layer of ferromagnetic material and the layer of 
antiferromagnetic material to be deposited non-sequentially and which 
requires lower anneal temperatures and shorter anneal times. First, 
depositing the layers non-sequentially allows the layer of 
magnetoresistive ferromagnetic material to be deposited, patterned and 
etched by whatever methods, and under whatever conditions, are most 
favorable. After patterning, etching and presputtering the layer of 
ferromagnetic material, the layer of antiferromagnetic material may be 
sputter deposited, with a low deposition power and in the absence of 
applied magnetic fields, onto the layer of ferromagnetic material. 
Thickness uniformities of the antiferromagnetic material are improved by 
depositing it in the absence of an applied field. Depositing at low power 
prevents the antiferromagnetic material from penetrating the layer of 
ferromagnetic material. Finally, the layers of ferromagnetic and 
antiferromagnetic material may be annealed at lower temperatures and over 
shorter time periods than are required by prior art methods of producing 
magnetoresistive read transducers with exchange stabilization. The 
magnetoresistive read transducer of the present invention exhibits very 
high exchange coupling, produced at a low anneal temperature in a single 
anneal cycle, without the use of interdiffusion materials. 
The method of producing a magnetoresistive read transducer of the present 
invention includes depositing a layer of magnetoresistive ferromagnetic 
material. The magnetoresistive ferromagnetic material is patterned and, 
etched. Before the layer of antiferromagnetic material is sputter 
deposited onto the layer of ferromagnetic material, the ferromagnetic film 
is presputtered to remove surface oxide such that the layer of 
antiferromagnetic material is in direct contact with the layer of 
ferromagnetic material. Finally, the layers of ferromagnetic material and 
antiferromagnetic material are annealed. 
In some preferred embodiments of the present invention, the layer of 
antiferromagnetic material is sputter deposited in an applied magnetic 
field of between 0 and 50 Oe. 
In other preferred embodiments of present invention, the layer of 
antiferromagnetic material is sputter deposited with a deposition power of 
between about 60 and 200 W (power densities of about 0.2 to 0.7 
W/cm.sup.2).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 are layer diagrams of MR head 10. MR head 10 includes layer 
of basecoat oxide 12, bottom shield layer 14, lower gap oxide layer 16, MR 
sensor 18, antiferromagnetic layer portions 20 and 22, and contacts 24 and 
26. MR sensor 18 is a layer of magnetoresistive ferromagnetic material. In 
preferred embodiments, MR sensor 18 is a layer of permalloy (NiFe). 
Antiferromagnetic layer portions 20 and 22 consist, in preferred 
embodiments, of a layer of FeMn. In most preferred embodiments, layer 
portions 20 and 22 consist of FeMn with 50 percent Fe and 50 percent 
manganese. 
As can be seen from FIG. 1, bottom shield layer 14 is deposited on top of 
basecoat oxide layer 12. Lower gap oxide layer 16 is deposited on top of 
bottom shield layer 14. MR sensor or NiFe layer 18 is deposited on top of 
lower gap oxide layer 16. Antiferromagnetic or FeMn layer portions 20 and 
22 are deposited directly on top of NiFe layer 18. Finally, contacts 24 
and 26 are deposited directly on top of FeMn layer portions 20 and 22. 
In the preferred embodiments of the present invention, the method of 
fabricating MR head 10 is as follows. Base coat oxide layer 12, bottom 
shield layer 14 and lower gap oxide layer 16 are deposited under 
conventional thin film deposition techniques. MR sensor or NiFe layer 18 
and FeMn layer portions 20 and 22 are then deposited non-sequentially. 
That is, MR sensor or NiFe layer 18 is deposited using known deposition 
techniques and under any conditions necessary to obtain an MR sensor with 
favorable properties. Typically, NiFe sensor layer 18 is sputter deposited 
in the presence of an externally applied magnetic field. An externally 
applied magnetic field of about 50 Oe is frequently used to create the 
desired magnetic orientations in NiFe sensor layer 18. However, NiFe 
sensor layer 18 may be deposited under any desirable conditions. For 
instance, the externally applied magnetic field may be higher or lower 
than 50 Oe. 
Next, MR head 10 is removed from the deposition chamber and patterned and 
etched by conventional techniques. Because the wafer with MR head 10 was 
removed from the deposition chamber, approximately 30 Angstroms of the 
NiFe film oxidizes. Therefore, the next step of the fabrication technique 
of the present invention is to presputter NiFe sensor layer 18 to achieve 
a clean surface. Presputtering NiFe sensor layer 18 may be done under 
conventional methods. Typically, presputtering NiFe sensor layer 18 would 
include sputter etching layer 18 in a vacuum chamber to remove at least 30 
Angstroms. This will usually be sufficient to provide a clean surface for 
deposition of the FeMn. 
The next step in the method of producing an MR head in accordance with the 
present invention is to deposit FeMn layer portions 20 and 22 onto the 
surface of NiFe sensor layer 18. FeMn layer portions 20 and 22 are sputter 
deposited at a very low power and in the absence of any externally applied 
magnetic field. Depositing the FeMn at very low power promotes a sharp 
atomic interface between FeMn layer portions 20 and 22 and NiFe sensor 
layer 18, with very little inter penetration of the FeMn into the NiFe. 
This is one advantage of the method of the present invention over the 
prior art because inter penetration of the FeMn into NiFe sensor layer 18 
is undesirable. As described below, prior art methods of producing an MR 
head with high exchange coupling require deposition of the FeMn at a high 
power, for example, above 2.5 W/cm.sup.2. In preferred embodiments of the 
present invention, FeMn layer portions 20 and 22 are deposited at a 
deposition power of approximately 70 W (0.2 W/cm.sup.2). However, it is 
clear that other low deposition powers below 200 W (0.7 W/cm.sup.2) would 
suffice. It is important that the deposition power be sufficiently low so 
that no substantial penetration of the FeMn into the NiFe occurs. 
Depositing FeMn layer portions 20 and 22 in the absence of an applied 
magnetic field results in greatly improved thickness uniformities as 
compared to prior art methods of producing an MR head with high exchange 
coupling, all of which appear to require that the NiFe and FeMn layers be 
deposited sequentially in the presence of an externally applied magnetic 
field. The benefits of the low power, no-field FeMn deposition are 
discussed in greater detail below. 
Finally, MR head 10 is annealed for a single cycle at temperatures and over 
time periods which are low compared to most prior art techniques. As will 
be discussed later with reference to Table III, MR head 10 may be annealed 
for a single cycle of less than 24 hours at a temperature of less than 
250.degree. C. to obtain high exchange fields. In preferred embodiments of 
the present invention, MR head 10 is annealed for a period of between 6 
and 24 hours at a temperature between 200.degree. and 250.degree. C. 
As discussed above, prior art MR head fabrication techniques typically 
require that NiFe sensor layer 18 and FeMn layer portions 20 and 22 be 
deposited sequentially. In other words, the layers of NiFe and FeMn are 
typically sputter deposited onto a wafer one after the other without 
removing the structure from the deposition chamber. As is typical in these 
prior art fabrication techniques, the NiFe and FeMn layers are deposited 
with a high deposition power. A typical deposition power is, for example, 
2.6 W/cm.sup.2. In these prior art methods, NiFe sensor layer 18 is 
preferably deposited in the presence of an externally applied magnetic 
field in order to achieve proper magnetic domain orientation. If, as in 
most prior art methods, the external applied field is provided by 
permanent magnets attached to wafer holder, then FeMn layer portions 20 
and 22 would also be applied in the presence of the same externally 
applied magnetic field. Depositing FeMn layer portions 20 and 22 in the 
presence of an externally applied magnetic field results in substantial 
thickness non-uniformities of the FeMn layer. 
FIG. 3 is a graph illustrating exchange field H.sub.ex versus the thickness 
of the FeMn layer. As can be seen from FIG. 3, the magnitude of exchange 
field H.sub.ex increases slightly from 45 Oe to approximately 48 Oe as 
FeMn thickness increases from about 100 Angstroms to around 175 Angstroms. 
For FeMn thicknesses above 175 Angstroms, exchange field H.sub.ex remains 
relatively constant. However, it can also be seen that as the thickness of 
the FeMn layer falls below 100 Angstroms, the magnitude of exchange field 
H.sub.ex decreases rapidly. This is most likely due to incomplete coverage 
of the NiFe sensor layer with the FeMn layer. This data leads to the 
conclusion that, so long as complete coverage of the NiFe layer 18 with 
FeMn is achieved, exchange field H.sub.ex is substantially independent of 
the thickness of the FeMn layer. However, it is desirable in most MR head 
designs, to reduce the overall height of the structure. Therefore, it is 
highly advantageous to limit the thickness of the FeMn layer to around 150 
Angstroms. As is clearly shown in the graph of FIG. 3, increasing the 
thickness of the FeMn layer beyond 150 Angstroms produces very little 
increase in exchange field H.sub.ex magnitude. 
As previously discussed, it is extremely difficult to obtain thickness 
uniformities of better than .+-.10 percent in the FeMn layer when 
deposition of the FeMn layer is in the presence of an externally applied 
magnetic field. However, in the absence of an externally applied magnetic 
field, thickness uniformities of better than .+-.3 percent can be 
obtained. The present invention discloses a method of depositing FeMn 
layer portions 20 and 22 of MR head 10 in the absence of an applied 
magnetic field. However, as discussed next with reference to Tables I and 
III, the pre-annealing exchange field H.sub.ex obtained when depositing 
FeMn layer portions 20 and 22 in the absence of an applied magnetic field 
is significantly lower than the pre-annealing exchange field H.sub.ex 
obtained in the prior an methods in which the FeMn layer is deposited in 
an externally applied magnetic field. Table I summarizes deposition 
conditions and results for a number of test wafers deposited with a field 
under a known deposition method. All of the depositions shown in Table I 
include a layer of FeMn deposited on a NiFe sensor layer. The depositions 
were conducted with a deposition power of 200 W (0.7 W/cm.sup.2) in an 
externally applied field of 50 Oe, and with a pressure of 4 mTorr. Because 
the magnitude of exchange field H.sub.ex varies inversely in proportion to 
the thickness of NiFe sensor layer 18, Table I shows the actual exchange 
fields H.sub.ex obtained as well as exchange fields adjusted for a nominal 
NiFe thickness of 300 Angstroms. As can be seen, with a 300 Angstrom NiFe 
sensor layer, exchange fields H.sub.ex of between 48.7 Oe and 54.1 Oe were 
obtained. The high exchange fields H.sub.ex shown in Table I were obtained 
without annealing. This demonstrates that high exchange fields H.sub.ex 
obtained in prior art methods are unlikely to be the result of third 
element interdiffusion or extended annealing at high temperatures. 
Although the exchange fields obtained for the FeMn layers deposited on 
NiFe sensor layers with a moderate deposition power of 0.7 W/cm.sup.2 and 
in the presence of an applied field may be further increased with extended 
annealing at high temperature, the increase in the exchange field H.sub.ex 
obtained is not particularly useful. Initial exchange fields of 50 Oe 
result in an exchange field of 15-25 Oe at the 80.degree. C. operating 
temperature of most disc drives, which is sufficient for exchange 
stabilization of the NiFe MR sensor. 
TABLE I 
______________________________________ 
EXCHANGE FIELD FOR FeMn DEPOSITED ON NiFe IN 50 Oe FIELD 
NiFe Actual Adj. Hex 
Dep. # Dep. Temp thickness 
Hex(Oe) 
300 A NiFe 
Hc(Oe) 
______________________________________ 
3105 25 321 49.0 52.5 5.0 
3106 25 348 45.0 52.1 5.0 
3107 25 348 44.5 51.6 4.5 
3108 25 348 42.0 48.7 5.0 
3117 25 354 45.0 53.1 5.0 
3118 25 334 48.5 54.1 4.5 
3119 25 367 43.5 53.2 4.5 
3021 25 328 46.0 50.3 5.0 
______________________________________ 
Table II shows the test results of depositions of FeMn under a variety of 
conditions. Because the existence of an exchange field H.sub.ex makes it 
difficult to measure the thickness and sheet resistance of the FeMn, on 
some of the wafers shown in Table II, the FeMn was deposited on a glass 
substrate. Without the presence of a ferromagnetic sensor layer, no 
exchange coupling can result. Wafers 1A, A1 and A2 correspond to an FeMn 
layer deposited on a glass substrate in order to prevent the occurrence of 
an exchange field. Wafer 1A was deposited with a deposition power of 200 W 
and in an applied field of 50 Oe. Wafer A1, was deposited with a 
deposition power of 200 W, but in the absence of any external applied 
magnetic field. Like wafer A1, wafer A2 was deposited in the absence of an 
external applied field, but with a significantly lower deposition power of 
70 W. All depositions in table II were deposited with a Ar pressure of 4 
mTorr. 
TABLE II 
__________________________________________________________________________ 
COMISON OF FIELD AND NO-FIELD FeMn DEPOSITION CONDITIONS 
Dep. 
Target Thickness 
Hex Hex 
Power 
Substrate 
Dep. Uniformity 
(300A) 
(300A) 
Wafer Field 
** Voltage 
Rate 3" wafer 
preanneal 
(annealed) 
I.D. 
Base 
(Oe) 
(w) (V) (A/min) 
(%) (Oe) (Oe) 
__________________________________________________________________________ 
1A Glass 
50 200 850 205 11.61 NA NA 
X NiFe* 
50 200 850 NA NA 52 -- 
Al Glass 
0 200 1450 147 2.62 NA NA 
Y NiFe* 
0 200 1450 NA NA 29.0 -- 
A2 Glass 
0 70 925 61 1.45 NA NA 
Z NiFe* 
0 70 925 NA NA 36.7 51.8 
__________________________________________________________________________ 
X = Average of data from the wafers of Table I. 
Y = Average of data from 2 wafers 
Z = Average of data from the wafers of Table III. 
* = 300-370 A NiFe film. 
** = For a 3 inch round wafer, 200 watts deposition power corresponds to 
power density of approximately 0.7 W/cm.sup.2 and a 70 watts deposition 
power corresponds to a power density of approximately 0.2 W/cm.sup.2. 
As can be seen from the data in Table II, the FeMn thickness uniformities 
of wafers A1 and A2 show extreme improvement over the 11.61 percent FeMn 
thickness uniformity of wafer 1A. This highly advantageous result is 
clearly due to the absence of an applied field during deposition of the 
FeMn layer on wafers A1 and A2. However, it can also be seen from Table II 
that wafer A2 has a uniformity which is significantly better than that of 
wafer A1. Wafer A2 has a thickness uniformity of 1.45 percent as compared 
to the 2.62 percent thickness uniformity of wafer A1. This non-negligible 
and extremely valuable result appears to be due to the lower deposition 
power of wafer A2 as compared to wafer A1. 
Table II clearly shows that improvements in thickness uniformity can be 
obtained by depositing the layer of FeMn at lower deposition powers and in 
the absence of an applied of an magnetic field. However, another important 
result is also shown in the data of Table II. The average results of Table 
I are shown in the second row of Table II and are generically labelled as 
wafer X. These results once again show that a high exchange field of 
approximately 52 Oe can be obtained by depositing the layer of FeMn on the 
layer of NiFe in an applied field of 50 Oe and with a deposition power of 
200 W. The fourth row, which corresponds to an average generically labeled 
as wafer Y, shows that while depositing the layer of FeMn at the higher 
power of 200 W but in the absence of an applied field may result in 
improved thickness uniformity, the resulting exchange field H.sub.ex is 
significantly lower than the exchange field obtained with a 200 W 
deposition power and a 50 Oe applied field. The most significant results 
are shown in row six, which is an average of deposition data from Table 
III which will be discussed below. This row is generically labelled as 
wafer Z. The data of row six shows that the pre-annealed exchange field 
for the 70 W deposition averages about 8 Oe higher than the 200 W no field 
deposition. After a single annealing, however, the average of the exchange 
fields H.sub.ex rises to 51.8 Oe, nearly as high as the high exchange 
field obtained when depositing at 200 W in a 50 Oe applied field. 
Table III shows data which further explores the results obtained with the 
improved method of producing MR heads with high exchange coupling of the 
present invention. Table III shows the effects of various annealing 
temperatures and time periods on MR heads in which FeMn layer portions 20 
and 22 were deposited at a low power of 70 W and in the absence of an 
external applied magnetic field. 
All of the MR heads used to obtain the data of Table III were deposited 
under the no-field low power non-sequential FeMn deposition technique of 
the present invention. The anneal temperatures range from 212.degree. C. 
to 247.degree. C. The anneal times range from 7 hours to 26 hours. As can 
be seen by the before anneal exchange fields obtained for a nominal NiFe 
thickness of 300 Angstroms, the before anneal exchange fields obtained 
with the method of the present invention are far lower than exchange 
fields obtained under prior art sequential deposition techniques. The 
before anneal adjusted exchange fields range from 33.4 Oe to 40.0 Oe. 
However, as can be seen from the after anneal exchange fields adjusted for 
a nominal NiFe thickness of 300 Angstroms, very significant improvement in 
the exchange field H.sub.ex can be obtained under the method of the 
present invention with a single very short anneal cycle at a temperature 
which is significantly lower than most prior art methods. After anneal, 
the adjusted exchange field H.sub.ex for all wafers increased 
significantly. The after anneal exchange fields H.sub.ex for the 10 wafers 
in Table III ranged from 47.3 Oe to 59.2 Oe. 
TABLE III 
______________________________________ 
EXCHANGE FIELD FOR FeMn DEPOSITED ON NiFe 
WITHOUT FIELD 
Anneal Anneal Final 
Waf Temp Time t.sub.FeMn 
H.sub.ex 
H.sub.ex @ 
H.sub.ex 
H.sub.ex @ 
# (.degree.C.) 
(Hr) (A) dep'd 
300A H.sub.c 
dep'd 
300A H.sub.c 
______________________________________ 
1 228 19 348 34.5 40.0 9.5 41.0 47.5 5.0 
2 226 7 374 31.0 38.6 6.0 38.0 47.3 5.0 
3 230 26 346 30.0 34.6 8.0 47.5 54.8 10.5 
4 225 13 334 30.0 33.4 8.0 45.0 50.1 9.0 
5 225 12 307 34.0 34.8 7.0 50.0 51.2 8.0 
6 225 11 329 30.5 33.4 7.5 45.0 49.4 8.0 
7 227 19 348 32.5 37.7 6.5 51.0 59.2 7.0 
8 212 9 335 34.5 38.5 7.0 43.0 48.0 7.0 
9 247 11 325 34.0 36.8 8.0 53.0 57.4 9.0 
10 228 13 343 34.0 38.9 8.0 46.0 52.6 6.0 
______________________________________ 
A very important aspect of the method of present invention is that the FeMn 
layer portions 20 and 22 may be deposited using the significantly more 
manufacturable no-field low power non-sequential method disclosed, while 
high exchange fields can still be obtained with a single short anneal 
cycle at a relatively low temperature. The low power deposition prevents 
FeMn penetration of the NiFe layer. The no-field aspect of the-deposition 
provides improved FeMn thickness uniformity. The low anneal temperatures 
and times make the inventive method of producing MR heads with high 
exchange coupling substantially more manufacturable than prior art 
methods. 
FIG. 4 is a graph showing exchange fields H.sub.ex versus temperature for 
NiFe/FeMn film couples produced according to the present invention and 
annealed under four different conditions. It can be seen that annealing at 
a high temperature of 275.degree. C. for 48 hours will result in higher 
exchange fields. Since an exchange field H.sub.ex of 20 Oe should be quite 
adequate for exchange stabilization, the increase is not overly 
significant at the 80.degree. C. operating temperature of most disc 
drives. Therefore, the method of the present invention is shown to provide 
more than adequate exchange fields at disc drive operating temperatures 
with anneal conditions significantly lower than prior art methods. 
The method of the present invention produces an MR transducer having 
improved longitudinal bias due to high exchange coupling. The low 
deposition powers necessary in the present invention prevent substantial 
penetration of the FeMn into the NiFe. Depositing the FeMn layer in the 
absence of significant magnetic fields produces better uniformity in the 
FeMn film. This in turn provides many advantages, including the fact that 
thinner FeMn films may be utilized without risking incomplete coverage of 
the NiFe film. The low anneal temperatures and short anneal times 
necessary to achieve high exchange coupling greatly increase 
manufacturability over prior art techniques. 
It must be noted that the method of the present invention of producing 
magnetoresistive read transducers with high exchange coupling can be 
modified slightly for other related applications while still achieving 
similar improved results. For instance, as discussed and shown above, the 
low power no-field FeMn deposition and the subsequent short time and low 
temperature annealing aspects of the present invention result in FeMn 
films which have greatly improved thickness uniformity and very little 
penetration of the FeMn into the magnetoresistive ferromagnetic film on 
which the FeMn is deposited. These improvements over prior art methods of 
producing magnetoresistive transducers are realized while still achieving 
exchange bias fields which are similar in magnitude to those achieved in 
many prior art methods. 
The improved thickness uniformity and lack of interpenetration of FeMn into 
the magnetoresistive film provides the capability of utilizing FeMn film 
layers as the anti-ferromagnetic spacing layer in "spin valve" or giant 
magnetoresistive effect transducers. A "spin-valve" or giant MR device is 
a multi-layered "sandwich" including either: (1) alternating layers of a 
magnetoresistive material such as CO or Fe and a non-magnetic metal such 
as Au or Cu; or (2) a similar set of alternating films, except that 
permalloy is part of the repeating sandwich. 
In some embodiments of giant MR devices an antiferromagnetic film such as 
FeMn replaces the non-magnetic film. In these embodiments, the present 
invention provides highly desirable film properties for the sandwich 
layers. The thickness uniformity provided by the present invention 
provides a substantial advantage in the manufacture of giant MR devices 
because of the extreme sensitivity of these devices to the thickness of 
the spacing layer. The sharp atomic interface produced by the low power 
deposition is necessary for giant MR devices. Also, inter-penetration of 
the layers degrades the giant MR effect. This undesirable result is 
avoided with the method of the present invention. Therefore, with slight 
modifications, the present invention could be used in the production of 
giant MR devices. 
Although the present invention has been described with reference to 
preferred embodiments, workers skilled in the art will recognize that 
changes may be made in form and detail without departing from the spirit 
and scope of the invention.