Spin valve sensor with enhanced magnetoresistance

A spin valve magnetoresistive (MR) read sensor is provided wherein the free and pinned layer magnetization are perpendicular to each other under quiescent conditions and the current flowing in the free MR layer is oriented to flow at a substantially 45 degree angle with respect to the free layer magnetization. The flow of the current at the 45 degree angle with respect to the free layer magnetization causes the AMR effect which is present in the free MR layer to be added to the spin valve sensor GMR effect and increases the overall magnetoresistive effect by about 25% to 33%.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates in general to a magnetoresistive read sensor for 
reading signals recorded in a magnetic medium and, more particularly, this 
invention relates to a spin valve magnetoresistive read sensor with 
enhanced giant magnetoresistance effect. 
2. Description of the Background Art 
A magnetoresistive (MR) read sensor, commonly referred to as an MR head, 
has been shown to be capable of reading data from a surface of a magnetic 
disk at greater linear densities than thin film inductive heads. An MR 
sensor detects a magnetic field through the change in the resistance of 
its MR sensing layer (also referred to as "MR element") as a function of 
the strength and direction of the magnetic flux being sensed by the MR 
sensing layer. MR read sensors are of great interest for several reasons: 
MR sensors' intrinsic noise is lower than inductive sensors' intrinsic 
noise, thus providing improved signal-to-noise (S/N) performance; MR 
sensors sense magnetic flux (.phi.) as compared to inductive heads which 
sense the time rate of flux change, d.phi./dt, thus making the 
reproduction of the signal recorded on a medium independent of the 
relative velocity between the MR sensor and the medium; and MR sensors 
have bandwidth in the gigahertz (gHz) range which allows area storage 
density well in excess of one gigabit per square inch. 
MR sensors currently being used or under development fall into two broad 
categories: 1) anisotropic magnetoresistive (AMR) sensors manifesting the 
AMR effect and 2) giant magnetoresistive (GMR) sensors manifesting the GMR 
effect. 
In the AMR sensors, the electron scattering and therefore the resistance of 
the MR layer varies as the function of cos.sup.2 .alpha. where .alpha. is 
the angle between the magnetization of the MR layer and the direction of 
the sense current flowing in the MR layer (FIG. 1A). The electron 
scattering and therefore the resistance is highest for the case where the 
magnetization of the MR layer is parallel to the current and minimum when 
the magnetization of the MR layer is perpendicular to the current. U.S. 
Pat. No. 5,018,037 entitled "Magnetoresistive Read Transducer Having Hard 
Magnetic Bias", granted to Krounbi et al. on May 21, 1991, discloses an MR 
sensor operating on the basis of the AMR effect. 
FIG. 1B shows a prior art AMR sensor comprising a ferromagnetic MR layer of 
NiFe exhibiting about 2% magnetoresistive effect (i.e., .DELTA.R/R=2%). 
In the GMR sensors, the resistance of the MR sensing layer, varies as a 
function of the spin-dependent transmission of the conduction electrons 
between the magnetic layers separated by a non-magnetic layer and the 
accompanying spin-dependent scattering which takes place at the interface 
of the magnetic and nonmagnetic layers and within the magnetic layers. 
GMR sensors using only two layers of ferromagnetic material (e.g., NiFe or 
Co or NiFeCo or NiFe/Co) separated by a layer of non-magnetic metallic 
material (copper) are generally referred to as spin valve (SV) sensors. In 
an SV sensor, one of the ferromagnetic layers, referred to as the pinned 
layer, has its magnetization typically pinned by exchange coupling with an 
antiferromagnetic (e.g., NiO or FeMn) layer. The pinning field generated 
by the antiferromagnetic layer is usually several hundred Oersteds so that 
the magnetization direction of the pinned layer remains fixed during the 
application of external fields (e.g., fields from bits recorded on the 
disk). The magnetization of the free ferromagnetic layer, however, is not 
fixed and is free to rotate in response to the field from the disk. FIG. 
2A shows a prior art SV sensor having a free MR layer separated from an MR 
pinned layer by a non-magnetic electrically-conducting spacer layer and 
further having an anti-ferromagnetic layer for pinning the MR pinned 
layer. 
In an SV sensor, the GMR effect depends on the angle between the 
magnetizations of the free and pinned layers. More specifically, the GMR 
effect is proportional to the cosine of the angle .beta. between the 
magnetization vector of the pinned layer (M.sub.P) and the magnetization 
vector of the free layer (M.sub.F) (FIGS. 2B and 2C). In an SV sensor, the 
electron scattering and therefore the resistance is maximum when the 
magnetizations of the pinned and free layers are antiparallel, i.e., 
majority of the electrons are scattered as they try to cross the boundary 
between the MR layers. On the other hand, electron scattering and 
therefore the resistance is minimum when the magnetizations of the pinned 
and free layers are parallel; i.e., majority of electrons are not 
scattered as they try to cross the boundary between the MR layers. 
In other words, there is a net change in resistance of an SV sensor between 
parallel and antiparallel magnetization orientations of the pinned and 
free layers. The GMR effect, i.e., the net change in resistance, exhibited 
by a typical prior art SV sensor is about 3% to 4%. U.S. Pat. No. 
5,206,590 entitled "Magnetoresistive Sensor Based On The Spin Valve 
Effect", granted to Dieny et al. on Apr. 27, 1993, discloses an MR sensor 
operating on the basis of the spin valve effect. 
MR sensors further fall into two configurations. In one configuration, the 
sense current is conducted in the MR sensing element parallel to the air 
bearing surface. Air bearing surface (ABS) refers to the surface of the 
slider and head adjacent the magnetic disk surface. In the other 
configuration, the sense current is conducted in the MR sensing element 
perpendicular to the air bearing surface. The former configuration is 
referred to as a horizontal MR read sensor and the latter configuration is 
referred to as an orthogonal MR read sensor. 
FIG. 3A shows a perspective view of a horizontal MR sensor 10 having 
passive end regions 12 and 14 separated by an active central region 16. An 
MR sensing element 18 having a read surface 20 above a circular track 30 
of a storage medium is formed in the central region 16. Read surface 20 
forms a part of the air bearing surface 22. In the horizontal MR sensor 
10, the MR sensing layer 18 is physically oriented such that its 
longitudinal axis, and hence its easy axis, is parallel to the trackwidth 
W of the circular track 30. Note that in the horizontal MR sensor 10 both 
leads are at the ABS. 
FIG. 3B shows a perspective view of an orthogonal MR sensor 10' having 
passive end regions 12' and 14' separated by an active central region 16'. 
An MR sensing layer 18' having a read surface 20' above a circular track 
30' of a storage medium is formed in the central region 16'. Read surface 
20' forms a part of the air bearing surface 22'. In the orthogonal MR 
sensor 10', the MR sensing layer 18' is physically oriented such that its 
longitudinal axis, and hence its easy axis, is parallel to the trackwidth 
W' of the circular track 30'. Note that in the orthogonal MR sensor 10' 
only one of the leads is at the ABS. 
As it was stated earlier, the magnetoresistance of a spin valve sensor is a 
function of the angle between the magnetizations of the free and pinned 
layers. The resistance increases as the angle between the M.sub.P and 
M.sub.F increases (i.e., as M.sub.P and M.sub.F become antiparallel) and 
resistance decreases as the angle between M.sub.P and M.sub.F decreases 
(i.e., as M.sub.P and M.sub.F become parallel). These resistance changes 
are independent of the direction of the sense current. 
However, it is very important to note that the magnetization rotation in 
the free MR layer also gives rise to anisotropic magnetoresistance (AMR) 
effect which does depend on the angle between the free layer magnetization 
vector and the current flowing in the free layer. In other words, in an SV 
sensor, the GMR effect and the AMR effect are both present and for optimum 
sensitivity (i.e., optimum magnetoresistance), the contributions of both 
effects should be utilized. The prior art spin valve sensors have not 
utilized the contribution of the AMR effect present in the free layer in 
order to increase the overall sensitivity of the spin valve sensors. 
As mentioned earlier, in conventional MR heads having an NiFe MR layer, the 
AMR effect is about 2%. In SV sensors, the AMR effect is somewhat reduced 
due to partial current shunting through the copper spacer and the pinned 
layer. Despite the partial shunting, an AMR effect of about 1% is 
generally observed in the SV sensors. Adding the AMR effect of about 1% to 
a typical spin valve GMR effect of about 3% to 4% can increase the overall 
magnetoresistance effect of the SV sensors by about 33% to 25%, 
respectively. 
Referring to FIG. 4A, there is shown a depiction of a free layer 40 and a 
pinned layer 50 of a prior art SV sensor 48. In this type of SV sensors, 
the pinned layer magnetization, M.sub.P, is generally oriented to be 
perpendicular to an air bearing surface 46. The current I.sub.1 which is 
that portion of the sense current that flows in the free layer is oriented 
to flow parallel to the longitudinal axis of the free layer (parallel to 
the ABS). The current I.sub.2 which is that portion of the sense current 
that flows in the pinned layer flows parallel to the longitudinal axis of 
the pinned layer (parallel to the ABS). The internal fields such as. 
ferromagnetic coupling, pinned layer demagnetizing field, and sense 
current I.sub.2 field are also balanced to ensure that the free layer 
magnetization M.sub.F is perpendicular to the pinned layer magnetization 
when the external field is zero. External field refers to the field from a 
magnetic medium which is sensed by the read head while flying in close 
proximity over the surface of the magnetic medium. The external field is 
either positive or negative depending on the polarity of the bits of 
information written onto the magnetic medium. It should be noted that in 
the SV sensor 48, edges 43 and 45 of leads 42 and 44, respectively, are 
perpendicular to the air bearing surface 46 and furthermore, leads 42 and 
44 form a contiguous junction with the free layer 40. In FIG. 4A, the 
short arrows 49 indicate the direction at which the current I.sub.1 flows 
in the free layer. 
Referring again to FIG. 4A and also to FIG. 4B, for external fields along 
the +y direction, the free layer magnetization vector M.sub.F rotates to 
the position M.sub.F1 forming the angle .alpha. with M.sub.P. Under this 
condition, AMR effect present in the free layer 40 and the GMR effect add 
to each other as shown by equation 1. 
EQU .DELTA.R1=-.DELTA.R.sub.GMR -R.sub.AMR ( Eq. 1) 
For external fields along the -y direction, the free layer magnetization 
vector M.sub.F rotates to the position M.sub.F2 forming the angle 
.alpha..sub.2 with M.sub.P. Under this condition, AMR effect of the free 
layer 40 subtracts from the GMR effect as shown by equation 2. 
EQU .DELTA.R2=+.DELTA.R.sub.GMR -.DELTA.R.sub.AMR ( Eq. 2) 
The net resistance change which is the difference between .DELTA.R1 and 
.DELTA.R2 is: 
EQU .DELTA.R=2.DELTA.R (GMR) (Eq. 3) 
Close inspection of Eq. 3 reveals that in this type of spin valve sensor 
the net resistance change is only the function of the GMR effect and does 
not depend on the AMR effect present in the free layer 40. 
Therefore, there is a need for an invention which teaches how to 
substantially eliminate the aforementioned problem and at the same time 
increase the magnetoresistive effect of SV sensors by ensuring that the 
net MR effect depends on the AMR effect of the free layer and the GMR 
effect of the SV sensor regardless of the direction of the external field. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to disclose a spin valve sensor 
with an improved MR effect. 
It is another object of the present invention to disclose a horizontal spin 
valve sensor having an improved MR effect. 
It is another object of the present invention to disclose an orthogonal 
spin valve sensor having an improved MR effect. 
It is yet another object of the present invention to disclose a spin valve 
sensor where the MR effect is independent of the direction of external 
fields. 
These and other objects and advantages are attained in accordance with the 
principles of the present invention by a spin valve read sensor where the 
current flowing in the free layer (I.sub.1) is oriented to flow in the 
direction which is substantially at a 45 degree angle relative to the free 
layer magnetization vector. Orienting the current (I.sub.1) to flow at a 
substantially 45 degree angle with respect to the free layer magnetization 
vector causes the AMR effect of the free layer to always add to the GMR 
effect of the spin valve sensor in the presence of an external field, 
regardless of the direction of the external field, thus increasing the 
overall MR effect of the SV sensor. 
The I.sub.1 current is oriented to flow at a substantially 45 degree angle 
with respect to the free layer magnetization vector by using electrical 
leads (current carrying leads, leads, contacts) having a slanted 
conducting edge. Unlike the conventional practice, the slanted conducting 
edge (canted conducting edge) forms a non-zero but less than 90 degree 
angle with respect to the free layer magnetization vector M.sub.F. In the 
preferred embodiment, the slanted conducting edge is contiguous with the 
free layer, meaning that it overlays and makes physical contact with the 
top surface of the free layer. Furthermore, in the preferred embodiment, 
the slanted conducting edge makes a 45 degree angle with respect to the 
free layer magnetization vector and the ABS. Since the I.sub.1 current 
flows perpendicular to the slanted conducting edges, it will then flow in 
the free layer at a 45 degree angle with respect to the free layer 
magnetization vector.

BEST MODE FOR CARRYING OUT THE INVENTION 
The following description is the best mode presently contemplated for 
carrying out the invention. This description and the number of alternative 
embodiments shown are made for the purpose of illustrating the general 
principle of the present invention and is not meant to limit the inventive 
concepts claimed herein. 
Referring now to FIG. 5, although the invention is described as embodied in 
a magnetic disk storage system as shown in FIG. 5, it will be apparent 
that the invention is also applicable to other magnetic recording systems 
such as a magnetic tape recording system. As shown in FIG. 5, at least one 
rotatable magnetic disk 512 is supported on a spindle 514 and rotated by a 
disk drive motor 518. The magnetic recording media on each disk is in the 
form of an annular pattern of concentric data tracks (not shown) on disk 
512. 
At least one slider 513 is positioned on the disk 512, each slider 513 
supporting one or more magnetic read/write heads 521. As the disks rotate, 
slider 513 is moved radially in and out over disk surface 522 so that 
heads 521 may access different portions of the disk where desired data is 
recorded. Each slider 513 is attached to an actuator arm 519 by means of a 
suspension 515. The suspension 515 provides a slight spring force which 
biases slider 513 against the disk surface 522. Each actuator arm 519 is 
attached to an actuator means 527. The actuator means as shown in FIG. 5 
may be a voice coil motor (VCM). The VCM comprises a coil movable within a 
fixed magnetic field, the direction and speed of the coil movements being 
controlled by the motor current signals supplied by controller 529. 
During operation of the disk storage system, the rotation of disk 512 
generates an air bearing between slider 513 and disk surface 522 which 
exerts an upward force or lift on the slider. The air bearing thus 
counter-balances the slight spring force of suspension 515 and supports 
slider 513 off and slightly above the disk surface by a small, 
substantially constant spacing during normal operation. 
The various components of the disk storage system are controlled in 
operation by control signals generated by control unit 529, such as access 
control signals and internal clock signals. Typically, control unit 529 
comprises logic control circuits, storage means and a microprocessor. The 
control unit 529 generates control signals to control various system 
operations such as drive motor control signals on line 523 and head 
position and seek control signals on line 528. The control signals on line 
528 provide the desired current profiles to optimally move and position 
slider 513 to the desired data track on disk 512. Read and write signals 
are communicated to and from read/write heads 521 by means of recording 
channel 525. 
The above description of a typical magnetic disk storage system, and the 
accompanying illustration of FIG. 5 are for representation purposes only. 
It should be apparent that disk storage systems may contain a large number 
of disks and actuators, and each actuator may support a number of sliders. 
Now referring to FIGS. 6A and 6B, there is shown an air bearing surface 
view and a perspective view, not to scale, of a spin valve sensor 600 of 
the preferred embodiment of the present invention comprising passive end 
regions 610 and 620 separated by a central active region 630. A magnetic 
shield layer 650 and a gap layer 648 are sequentially formed on a suitable 
substrate 652. Shield layer 650 provides magnetic isolation for MR sensor 
600 and is typically made of NiFe or sendust (TM). Gap layer 648 provides 
electrical isolation for SV material 660 and is generally made of Al.sub.2 
O.sub.3 or SiO.sub.2. After forming gap layer 648, an anti-ferromagnetic 
layer 646, a pinned MR layer 644, a spacer 642 and a free MR layer 632 are 
then formed in that order on central region 630 over gap layer 648. Layers 
632, 642, 644, and 646 are collectively referred to as SV sensing element 
(also sensing material) 660. Anti-ferromagnetic (AFM) layer 646 is used to 
pin the magnetization of the pinned layer 644 in a fixed direction. In the 
preferred embodiment of the present invention, the pinned layer 
magnetization is fixed to be perpendicular to the ABS 636. AFM layer 646 
is typically made of FeMn, NiO or NiMn. MR layer 644 with its 
magnetization pinned in a fixed direction (thus the terminology pinned MR 
layer 644) is made of soft ferromagnetic material, preferably cobalt (Co). 
Nonmagnetic metallic spacer 642 is preferably made of copper (Cu) although 
other noble elements may also be used. Free MR layer 632 with its 
magnetization free to rotate under the presence of an external field is 
made of soft ferromagnetic material, preferably NiFe or NiFe/Co. 
Magnetization of the free layer 632 is set to be perpendicular to the 
pinned layer magnetization in the absence of an external field. 
Hard bias layers 612 and 622 which are formed in end regions 610 and 620, 
respectively, provides a longitudinal bias field which ensures a single 
magnetic domain state for SV material 660 in central region 630. Hard bias 
layers 612 and 622 are preferably made of CoPtCr, CoPtCrTa or 
CoPtCrSiO.sub.2. Hard bias layers 612 and 622 further form contiguous 
junctions with the SV material 660. 
Trapezoidal electrical leads 680 and 690 are then deposited over hard bias 
layers 612 and 622 in the passive end regions 610 and 620, respectively, 
as well as being deposited over a portion of surface 634 of the free MR 
layer 632. Trapezoidal leads 680 and 690 have slanted conducting edges 682 
and 692, respectively. The slanted conducting edges 682 and 692 are 
contiguous (i.e., overlay and make physical contacts) with the free layer 
632. In the preferred embodiment of the present invention, the slanted 
conducting edges 682 and 692 are formed only in the central region 630 and 
are contiguous only with the surface 634 of the free layer 632 and extend 
the full height 666 of the free layer 632. In the preferred embodiment, 
the small angle between the slanted conducting edges 682 and 692 and the 
ABS 636 are about 45 degrees. 
A sense current source 740 (FIG. 7A) is electrically connected to the leads 
680 and 690 for providing a sense current which is conducted through the 
spin valve sensor 600. A sensing circuit 750 is also electrically 
connected to leads 680 and 690, in parallel with the sense current source 
740, for sensing potential changes across the SV sensor 600 when the SV 
sensor 600 is exposed to external fields from a disk. 
Referring now to FIGS. 7A and 7B, there are shown a perspective view of the 
free layer 632 (as well as the leads 680 and 690 and a portion of the hard 
bias layers 612 and 622) and the pinned layer 644 of the SV sensor 600 of 
FIG. 6B and a diagram of the magnetization vectors M.sub.F and M.sub.P in 
the absence of an external field and in the presence of positive and 
negative external fields, respectively. 
Now referring to FIGS. 6A, 6B, 7A and 7B, pinned layer magnetization, 
M.sub.P, is pinned in the direction of +y-axis and directed away from the 
air bearing surface (ABS) such that M.sub.P is perpendicular to the 
longitudinal axis of the pinned layer 644 (i.e., perpendicular to the 
ABS). 
Once the direction of the M.sub.P is fixed, then the internal fields such 
as ferromagnetic coupling, pinned layer demagnetizing field, and I.sub.1 
field are balanced to ensure that at the quiescent bias point (in the 
absence of an external field such as a field from the disk), the free 
layer magnetization vector, M.sub.F, is perpendicular to the pinned layer 
magnetization vector M.sub.P in the direction of +x-axis (M.sub.F becomes 
parallel to the ABS as a result of being perpendicular to M.sub.P). 
Now referring again to FIG. 7A, note that a portion of the sense current 
I.sub.S flows in the free layer (designated as I.sub.1) and a portion of 
the sense current Is flows in the pinned layer (designated as I.sub.2). 
Furthermore, the I.sub.1 current flows from the slanted conducting edge 
682 into free layer 632 in a 45 degree angle with respect to the free 
layer magnetization vector. Short arrows 649 indicate the direction at 
which the current I.sub.1 flows. The 45 degree orientation of the current 
I.sub.1 is achieved because I.sub.1 current flows perpendicular to the 
slanted conducting edge 682 which forms a 45 degree angle with the M.sub.F 
and the ABS 636 of the SV sensor 600. It will be shown below that when 
current flows at a 45 degree angle with respect to the free layer 
magnetization at the quiescent condition (i.e., no external field 
present), the spin valve GMR effect and the AMR effect do add to each 
other thus increasing the net magnetoresistance of the SV sensor. 
Referring again to FIGS. 7A and 7B, at the quiescent bias point the 
magnetizations of the pinned (M.sub.P) and free (M.sub.F) layers are 
perpendicular to each other (i.e., the magnetization vectors are at 90 
degree with respect to each other) and current I.sub.1 direction forms a 
45 degree angle with the free layer magnetization vector. In the presence 
of external fields along the +y direction, the free layer magnetization 
vector M.sub.F rotates to the position M.sub.P1 toward becoming parallel 
with M.sub.P. As M.sub.F rotates toward becoming parallel with Mp (forming 
the angle .alpha..sub.1), the resistance decreases because of spin valve 
effect in the SV sensor 600 as well as the AMR effect in the free layer 
632. Under this condition, AMR effect present in the free layer and the 
GMR effect, both having the same sign, are added to each other as shown by 
equation 4. 
EQU .DELTA.R1=-.DELTA.R.sub.GMR -.DELTA.R.sub.AMR (Eq. 4) 
In the presence of external fields along the -y direction, the free layer 
magnetization vector M.sub.P rotates to the position M.sub.F2 toward 
becoming antiparallel with M.sub.P (forming the angle .alpha..sub.2). As 
M.sub.P rotates toward becoming antiparallel with respect to the M.sub.P, 
resistance increases because of spin valve effect as well as AMR effect in 
the free layer. Under this condition, the AMR effect of the free layer and 
the GMR effect of the SV sensor, both having the same sign, add up as 
shown by equation 5. 
EQU .DELTA.R2=+.DELTA.R.sub.GMR +R.sub.AMR (Eq. 5) 
The net resistance change which is the difference between .DELTA.R1 and 
.DELTA.R2 is: 
EQU .DELTA.R=.DELTA.R1-.DELTA.R2=2.DELTA.R (GMR)+2.DELTA.R (AMR)(Eq. 6) 
Close examination of equation 6 reveals that, according to the present 
invention, regardless of the direction of the external field (positive or 
negative external fields), the AMR effect of the free layer always adds to 
the GMR effect of the SV sensor and consequently, increases the 
magnetoresistive effect of the SV sensor. Since GMR effect is about 3% to 
4% and the AMR effect observed in SV sensors is about 1%, the present 
invention increases the total magnetoresistive effect of SV sensors by 
about 33% to 25%, respectively. 
Referring now to FIGS. 8A and 8B, there are shown a perspective view of an 
orthogonal SV sensor 800 of the present invention and a perspective view 
of free layer 832 and pinned layer 844 of orthogonal SV sensor 800, 
respectively. SV sensor 800 comprises passive end regions 810 and 820 
separated by a central active region 830. A magnetic shield layer 850 and 
a gap layer 848 are sequentially formed on a suitable substrate 852. After 
forming the gap layer 848, an anti-ferromagnetic layer 846, a pinned MR 
layer 844, a spacer 842 and a free MR layer 832 are then formed in that 
order on the central region 830 over the gap layer 848. MR layer 832 has 
side edges 836 and 838 which are substantially perpendicular to the ABS 
870. Layers 832, 842, 844, and 846 are collectively referred to as SV 
sensing element (also sensing material) 860. The anti-ferromagnetic (AFM) 
layer 846 is used to pin the magnetization of the pinned layer 844 in 
either the +y direction or -y direction. Magnetization of the free layer 
832 is then set to be perpendicular to the pinned layer magnetization in 
the absence of an external field. 
Hard bias layers 812 and 822 which are formed in the passive end regions 
810 and 820, respectively, provide a longitudinal bias field to ensure a 
single magnetic domain state for SV material 860 in central region 830. 
Hard bias layers 812 and 822 further form contiguous junctions with the SV 
sensing material 860. 
Trapezoidal leads 880 and 890 are then deposited over a portion of surface 
834 of the free MR layer 832. Trapezoidal leads 880 and 890 have slanted 
conducting edges 882 and 892, respectively. The slanted conducting edges 
882 and 892 are formed in the central region 830 and are contiguous (i.e., 
overlay and make physical contact) with the free layer 832. In this 
embodiment, the slanted conducting edges 882 and 892 extend the full width 
866 of the free layer 832 and further form a 45 degree angle with side 
edges 836 and 838 of the free layer 832, respectively. Note that a portion 
of the sense current I.sub.S flows in the free layer 832 (designated as 
I.sub.1) and a portion of the sense current I.sub.S flows in the pinned 
layer 844 (designated as I.sub.2). Furthermore, the I.sub.1 current flows 
from the slanted conducting edge 892 into free layer 832 in a 45 degree 
angle with respect to the free layer magnetization vector. Short arrows 
849 indicate the direction at which the current I.sub.1 flows. 
It is important to note that orienting the I.sub.1 current to flow at a 45 
degree angle with respect to the free layer magnetization vector is the 
optimum current flowing angle at which the contribution of the AMR effect 
present in the free layer to the overall sensitivity of the SV sensor is 
maximum. As the angle between the I.sub.1 current and the free layer 
magnetization vector approaches 0 degrees (current and the M.sub.F become 
parallel) or approaches 90 degrees (current and the M.sub.F approach to 
become perpendicular), the contribution of the AMR effect to the overall 
sensitivity of the SV sensor diminishes considerably. The shape of the 
electrical leads, specifically, the length and the placement of the 
slanted conducting edges have a substantial effect on the contribution of 
the AMR effect as shown in the alternative embodiments of FIGS. 9 and 10. 
Now referring to FIG. 9, there is shown a perspective view of a spin valve 
sensor 900 of an alternative embodiment of the present invention 
comprising passive end regions 910 and 920 separated by a central active 
region 930. A magnetic shield layer 950 and a gap layer 948 are 
sequentially formed on a suitable substrate 952. After forming the gap 
layer 948, an anti-ferromagnetic layer 946, a pinned MR layer 944, a 
spacer 942 and a free MR layer 932 are then formed in that order on 
central region 930 over gap layer 948. Layers 932, 942, 944, and 946 are 
collectively referred to as SV sensing element (also sensing material) 
960. Magnetization of the free layer 932 is set to be perpendicular to the 
pinned layer magnetization in the absence of an external field and thus 
parallel with the air bearing surface (ABS). 
Hard bias layers 912 and 922 formed in the passive end regions 910 and 920, 
respectively, provide a longitudinal bias field. Hard bias layers 912 and 
922 further form contiguous Junctions with the SV material 960 and have 
edges 914 and 924, respectively. Edges 914 and 924 are perpendicular to 
ABS 936. 
Triangular electrical leads 980 and 990 are then deposited over a portion 
of the passive end regions 910 and 920, respectively, as well as being 
deposited over a portion of the surface 934 of free MR layer 632. 
Triangular leads 980 and 990 have slanted conducting edges 982 and 992, 
respectively. Slanted conducting edge 982 overlay and makes physical 
contact with the hard bias layer 912 and the top surface 934 of the free 
MR layer 932. Likewise, the slanted conducting edge 992 overlay and makes 
physical contact with the hard bias layer 922 and the top surface 934 of 
the free MR layer 932. The slanted conducting edges 982 and 992 further 
form a 45 degree angle with the free layer magnetization vector and 
therefore, with the ABS 936 of the SV sensor 900 in the direction of the 
+x-axis. 
Note that in this embodiment, since each of the slanted conducting edges 
overlays and makes physical contact with both the hard bias material and 
the free MR layer 932, a portion of the current I.sub.1 flows at a 45 
degree angle with respect to the free layer magnetization (shown as 
I.sub.1A) and a portion of the current I.sub.1 flows parallel with respect 
to the free layer magnetization (shown as I.sub.1B). More specifically, 
current I.sub.1A which flows out of that portion of the slanted conducting 
edge 982 which is formed over the free layer 932 flows at a 45 degree 
angle with respect to the free layer magnetization and current I.sub.1B 
which flows out of that portion of the slanted conducting edge 982 which 
is formed over the hard bias layer 912 flows parallel with respect to the 
free layer magnetization due to the hard bias layer being a conductor 
itself. As a result, the contribution of the AMR effect to the overall 
magnetoresistance of the SV sensor 900 is less than the optimum condition 
(preferred embodiment shown in FIGS. 6A and 6B) when all of the I.sub.1 
current flows at a 45 degree angle with respect to the free layer 
magnetization vector. 
Now referring to FIG. 10, there is shown a perspective view of an SV sensor 
1100 of another alternative embodiment of the present invention comprising 
passive end regions 1110 and 1120 separated by a central active region 
1130. In this SV sensor, the pinned layer magnetization is set to be 
perpendicular to the air bearing surface 1136 and the magnetization of the 
free layer 1132 is set to be perpendicular to the pinned layer 
magnetization vector in the absence of an external field. Hard bias layers 
1112 and 1122 are formed in the passive end regions 1110 and 1120, 
respectively, and form contiguous junctions with the free layer 1132. 
Trapezoidal electrical leads 1180 and 1190 are then formed over passive end 
regions 1110 and 1120, respectively, as well as being formed over a 
portion of surface 1134 of the free MR layer 1132. Trapezoidal leads 1180 
and 1190 have slanted conducting edges 1182 and 1192, respectively. The 
slanted conducting edges 1182 and 1192 are formed over the free layer 1132 
in the central active region 1130, overlay and make physical contact with 
the surface 1134 of the free layer 1132. Furthermore, in this embodiment, 
the small angles between the slanted conducting edges 1182 and 1192 and 
the ABS 1136 are about 75 degrees. 
Note that in the embodiment of FIG. 10, since the angles between the 
slanted conducting edges 1182 and 1192 and the ABS 1136 are about 75 
degree angles, the angle between the sensing current and the free layer 
magnetization vector is about 15 degrees. As a result, the contribution of 
the AMR effect to the overall SV sensor magnetoresistive effect is less 
than the optimum condition when all the I.sub.1 current flows at a 45 
degree angle with respect to the free layer magnetization vector. 
While the present invention has been particularly shown and described with 
reference to the preferred embodiment thereof, nevertheless, it will be 
understood by those skilled in the art that various modifications may be 
made therein without departing from the spirit, scope, and teaching of the 
present invention. 
For example, although the preferred embodiment of the present invention was 
described in terms of a spin valve MR sensor where the sensing current 
flows at a 45 degree angle with respect to the free layer magnetization at 
the quiescent point, the invention is equally applicable to embodiments 
where the sensing current flows at any angle greater than zero and less 
than 90 degree with respect to the free layer magnetization vector. 
Furthermore, although the preferred embodiment and the alternative 
embodiments of the present invention were described in terms of a spin 
valve sensor having trapezoidal or triangular shape leads, the invention 
is equally applicable to embodiments where the leads have no commonly 
defined shape as long as each lead has a slanted conducting edge where the 
slanted conducting edge partially overlays and makes physical contact with 
a surface of the free MR layer and where the slanted conducting edge forms 
an angle greater than zero but less than 90 degrees with respect to the 
air bearing surface. 
Furthermore, although in the preferred embodiment of the present invention 
the pinned layer magnetization, M.sub.P, is pinned along the +y axis and 
directed away from the air bearing surface, it is well understood that 
M.sub.P could be pinned along the -y axis toward the ABS. 
Accordingly, it is to be understood that the invention disclosed herein is 
not to be limited by the illustrated embodiment, but only by the scope of 
the appended claims.