# Patent

## Title
Dual free layer magnetic reader having a rear bias structure having a high aspect ratio

## Abstract

A magnetic read apparatus has an air-bearing surface (ABS) and includes a read sensor and a rear magnetic bias structure. The read sensor includes first and second free layers, a spacer layer and a rear surface opposite to the ABS. The spacer layer is nonmagnetic and between the first and second free layers. The read sensor has a track width in a cross track direction parallel to the ABS. The rear magnetic bias structure magnetically biases the read sensor a stripe height direction perpendicular to the ABS. The read sensor is between the ABS and the rear magnetic bias structure. The rear magnetic bias structure has a width in the cross track direction and a length in the stripe height direction. The length is greater than the width. The width of the rear magnetic bias structure is substantially equal to the track width of the read sensor.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a continuation-in-part of co-pending U.S. patent application Ser. No. 14/670,340, filed on Mar. 26, 2015, (F7730), and incorporated herein by reference.


BACKGROUND
FIG. 1 depicts an air-bearing surface (ABS) view of a conventional read transducer used in magnetic recording technology applications. The conventional read transducer 10 includes shields 12 and 18, insulator 14, magnetic bias structures 16, and sensor 20. The read sensor 20 is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor. The read sensor 20 includes an antiferromagnetic (AFM) layer 22, a pinned layer 24, a nonmagnetic spacer layer 26, and a free layer 28. Also shown is a capping layer 30. In addition, seed layer(s) may be used. The free layer 28 has a magnetization sensitive to an external magnetic field. Thus, the free layer 28 functions as a sensor layer for the magnetoresistive sensor 20. If the sensor 20 is to be used in a current perpendicular to plane (CPP) configuration, then current is driven in a direction substantially perpendicular to the plane of the layers 22, 24, 26, and 28. Conversely, in a current-in-plane (CIP) configuration, then conductive leads (not shown) would be provided on the magnetic bias structures 16. The magnetic bias structures 16 are used to magnetically bias the free layer 28.
Although the conventional transducer 10 functions, there are drawbacks. The trend in magnetic recording is to higher density memories. The conventional read sensor 20 may not adequately read high density media. As a result, dual free layer magnetic read sensors have been developed. In such read sensors, two free layers that are biased in a scissor state by a hard magnet. The read sensor may not, however, be reliable in such a conventional magnetic reader. Such reliability issues may become particularly acute at high densities and lower track widths on the order of less than or equal to thirty nanometers. For example, in such high density dual free layer readers, the state in which the free layers are biased may be unpredictable. Accordingly, what is needed is a system and method for improving the performance of a magnetic recording read transducer.



BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 depicts an ABS view of a conventional magnetic recording read transducer.
FIGS. 2A-2C depicts ABS, plan and side views of an exemplary embodiment of a portion of a dual free layer magnetic read transducer.
FIGS. 3A-3B depict plan and side views of another exemplary embodiment of a portion of a dual free layer magnetic read transducer.
FIGS. 4A-4B depict plan and side views of another exemplary embodiment of a portion of a dual free layer magnetic read transducer.
FIGS. 5A-5B depict plan and side views of another exemplary embodiment of a portion of a dual free layer magnetic read transducer.
FIG. 6 depicts a side view of another exemplary embodiment of a portion of a dual free layer magnetic read transducer.
FIG. 7 depicts a side view of another exemplary embodiment of a portion of a dual free layer magnetic read transducer.
FIG. 8 is flow chart depicting an exemplary embodiment of a method for providing a magnetic recording read transducer.
FIG. 9 is flow chart depicting another exemplary embodiment of a method for providing a magnetic recording read transducer.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 2A-2C depict ABS, plan and side views of an exemplary embodiment of a portion of a magnetic read transducer 100. For clarity, FIGS. 2A-2C are not to scale. The read transducer 100 may be part of a read head or may be part of a merged head that also includes a write transducer. The head of which the read transducer 100 is a part is contained in a disk drive having a media, a slider and the head coupled with the slider. Further, only a portion of the components of the read transducer 100 are depicted.
The transducer 100 includes optional soft magnetic shields 102 and 104, insulator 106, read sensor 110, side bias structures 130 and 150 and rear bias structure 160 that may be separated from the read sensor 110 by an insulating layer 155. The read sensor 110 includes a first free layer 112 and a second free layer 116 separated by a nonmagnetic spacer layer 114. The nonmagnetic spacer layer 114 may be conductive or an insulating tunneling barrier layer, such as MgO. The read sensor 110 is, therefore, a giant magnetoresistive or tunneling magnetoresistive read sensor in the embodiment shown. The free layers 112 and 116 are ferromagnetic and may include multiple layers. The free layers 112 and 116 are biased such that their magnetic moments 113 and 117, respectively are in a scissor mode. Based on the angle between the magnetic moments 113 and 117, the resistance of the read sensor 110 changes. This angle changes when the read 110 is under the influence of an external field, for example due to a bit being read. Thus, the resistance of the read sensor 110 may be used to read data. The read sensor 110 may also be configured for high density recording. Thus, in some embodiments, the track width (TW) of the read sensor 110 is not more than thirty nanometers. In some such embodiments, the track width is not more than twenty nanometers. In the embodiment shown, the shields 102 and 104 and the free layers 112 and 116 all have a stripe height, SH, in the stripe height direction. In other embodiments, however, different structures 102, 104, 112 and 116 may have different stripe heights.
The transducer 100 includes side magnetic bias structures 120 and a rear magnetic bias structure 160 that together magnetically bias the free layers 112 and 116 in a scissor mode. As can be seen in FIGS. 2A and 2B, the side bias structures 120 bias the magnetic moments 113 and 117, respectively, of the free layers 112 and 116, respectively, parallel to the ABS, in the cross-track direction. The magnetic bias structures 120 and free layers 112 and 116 are also configured to bias the magnetic moments 113 and 117 of the free layers 112 and 116, respectively, antiparallel. In some embodiments, the magnetic moments 113 and 117 of the free layers 112 and 116 are antiferromagnetically coupled. The rear magnetic bias structure 160 biases the magnetic moments 113 and 117 of the free layers 112 and 116, respectively, perpendicular to the ABS, in the stripe height direction.
Each bias structure 120 includes two magnetic bias structures 130 and 150 separated by a nonmagnetic structure 140. The first magnetic bias structure 130 magnetically biases the free layer 112 and, therefore, is adjacent to the sides of the free layer in the cross-track direction. Similarly, the second magnetic bias structure 150 magnetically biases the free layer 116 and is thus adjacent to the side of the free layer 116 in the cross-track direction. In the embodiment shown, the top surface of the first magnetic bias structure 130 is not higher than the upper surface of the first free layer 112. However, in other embodiments, the top surface of the magnetic bias structure 130 may be at another location. In some embodiments, the top surface of the first magnetic bias structure 130 is not higher than the lower surface of the second free layer 116. In other embodiments, the top surface of the first magnetic bias structure 130 is not higher than midway between the upper and lower surfaces of the second free layer 116. Although the top of the first magnetic bias structure 130 may be higher than bottom of the second free layer 116, the entire magnetic bias structure 130 is still lower than the second magnetic bias structure 150. Similarly, the bottom surface of the second magnetic bias structure 150 is not lower than the lower surface of the second free layer 116 in the embodiment depicted in FIGS. 2A-2C. However, in other embodiments, the bottom surface of the magnetic bias structure 150 may be at another location. For example, the bottom surface of the second magnetic bias structure 150 may not be lower than the upper surface of the first free layer 112. In other embodiments, the bottom surface of the magnetic structure 150 is not lower than midway between the upper and lower surfaces of the first free layer 112. Although the bottom of the second magnetic bias structure 150 may be lower than upper surface of the first free layer 112, the entire magnetic bias structure 150 is still higher than the first magnetic bias structure 130.
The magnetic bias structures 130 and 150 may take various forms. In some embodiments, both the first magnetic bias structure 130 and the second magnetic bias structure 150 are soft magnetic structures. For example, the magnetic bias structures 130 and 150 may be an alloy, multilayer or other structure that has a coercivity of not more than ten Oe. In some such embodiments, the soft magnetic bias structure(s) 130 and/or 150 have a coercivity of not more than five Oe. For example, the magnetic bias structures 130 and 150 may include CoFe and/or NiFe. In other embodiments, the magnetic bias structures 130 and/or 150 may have different magnetic properties. In some embodiments, the magnetic bias structure 130 and/or 150 may be a hard bias structure. For example, the first magnetic bias structure 130 may be an alloy or multilayer that has a sufficiently high coercivity to have its magnetic moment 132 substantially unchanged during operation of the transducer 100. In other embodiments, the first magnetic bias structure 130 may be a pinned structure. In such an embodiment, the first magnetic bias structure 130 may include a pinning layer, such as an antiferromagnetic (AFM) layer and a soft magnetic layer adjoining the pinning layer. In still other embodiments, the magnetic bias structure 130 and 150 may be configured in another manner. For example, the shield 102 is shown as being overmilled to allow for the soft bias structures 130 and 150. However, in other embodiments, the shield 102 may not be overmilled.
The first magnetic bias structure 130 may have a magnetic moment 132. The second magnetic bias structure 152 may have a magnetic moment 152. As can be seen in FIG. 2B, the magnetic moments 132 and 152 are antiferromagnetically aligned. Stated differently, the steady state orientation of the magnetic moments 132 and 152 is antiparallel. In some embodiments, the bias structures 130 and 150, and thus the magnetic moments 132 and 152, are antiferromagnetically coupled. Because of the orientations of the magnetic moments 132 and 152, the magnetic moment 113 of the first free layer 112 is biased in one direction, while the magnetic moment 117 of the second free layer 116 is biased in the opposite direction.
The magnetic transducer 100 also includes a rear magnetic bias structure 160. The rear bias structure may be a soft magnetic bias structure, a hard magnetic bias structure, or include both soft and hard magnetic bias structures. For example, a hard magnetic bias structure may be a magnetic structure having a coercivity of greater than one hundred Oersted. In some embodiments, the hard magnetic bias structure coercivity is at least one thousand Oersted. In contrast, a soft magnetic bias structure may have a coercivity of less than one hundred Oersted. In some embodiments, the soft magnetic bias structure coercivity is not more than ten Oersted. The hard and soft bias structure may include single alloys, multiple layer(s), a mixed-composition alloy and/or other components. Other components, such as a pinning structure, may be included in the rear bias structure 160. A pinning structure is a magnetic component used to magnetically bias other portions of the rear magnetic bias structure 160. For example, the pinning structure might be an antiferromagnetic (AFM) layer.
The read sensor 110 is between the rear bias structure 160 and the ABS. Further, an insulating layer 155 may separate the rear bias structure 160 from the sensor 110 and bias structures 120. Such an insulating layer 155 may be used if the rear bias structure 160 is conductive. In addition, although the shields 102 and 104 are shown as extending only to the stripe height of the sensor 110, the shields 102 and 104 generally extend significantly further in the stripe height direction. However, the shields 102 and 104 are also magnetically decoupled from the rear bias structure 160. Thus, the insulating layer 155 and a top insulating (not shown) may extend along the depth of the rear bias structure 160. For example, in some embodiments, the insulating layer 155 is at least ten Angstroms and not more than forty Angstroms thick. The insulating layer 155 is also nonmagnetic. Thus, the read sensor 110 may be electrically insulated from the rear bias structure 160 and not exchanged coupled with the rear soft bias structure 160. Although not depicted in FIGS. 2A-2C, an insulating capping layer may also be provided on top of the rear bias structure 160.
The rear bias structure 160 is shown having a width, w, in the cross-track direction; a length, l, in the stripe height direction and a thickness, t, in the down track direction. The width of the rear bias structure 160 is substantially equal to the track width, TW, of the read sensor 110. In some embodiments, this is because the sensor 110 and rear bias structure 160 are defined in the cross-track direction using a single mask. Stated differently, the rear bias structure 160 and sensor 110 may be self-aligned. In addition, the length, l, is greater than the width (l≧w). Thus, the rear bias structure 160 has a shape anisotropy that is perpendicular to the ABS.
The magnetic moment 162 of the rear bias structure 160 is used to bias the sensor 110 in the stripe height direction. Consequently, the rear bias structure 160 has a magnetic anisotropy in the stripe height direction. This anisotropy may arise from one or more effects. For example, the rear bias structure 160 may have a shape anisotropy. In some embodiments, the length is at least four multiplied by the width. In some such embodiments, the length is at least ten multiplied by the width. The rear bias structure 160 may have a crystalline anisotropy that favors a perpendicular-to-ABS orientation of the magnetic moment 162. The rear bias structure 160 may have a magnetic anisotropy due to deposition in a magnetic field. In some embodiments, the rear bias structure 160 may have a magnetoelastic anisotropy, for example due to magnetostriction. In other embodiments, a pinning layer (not shown in FIGS. 2A-2C) or other structure (not shown) may be used to induce the magnetic anisotropy in the rear bias structure 160. In some embodiments, such a magnetic anisotropy is consistent with a reversal field of at least one thousand Oersted. In some such embodiments, the reversal field is at least five thousand Oersted.
Further, the rear bias structure 160 provides sufficient moment to bias the magnetic moments 113 and 117 of the free layers 112 and 116, respectively. For example, in some embodiments, the rear soft bias structure has a saturation magnetization-thickness product of at least one milli-emu/cm2 and not more than three milli-emu/cm2. In some such embodiments, the saturation magnetization-thickness product is not more than two milli-emu per cm2. The thickness used in the saturation magnetization-thickness product is t, the depth of the rear bias structure 160 in the down track direction.
The magnetic transducer 100 may be suitable for use in high density magnetic recording applications, for example those having a sensor track width (and thus rear bias structure 160 width) of not more than thirty nanometers. In some embodiments, the track width and rear bias structure width may be not greater than twenty nanometers. The read sensor 110 may not include an antiferromagnetic layer or a pinned layer. Consequently, the shield-to-shield spacing (SS1) between the shields 102 and 104 may be reduced. The use of the scissor mode may also enhance the read signal. This scissor mode may be more reliably achieved because of the presence of the rear bias structure 160. In particular, the shape anisotropy, width and other aspects of the rear bias structure 160 may allow for more reliable biasing of the read sensor. The desired scissor mode may be achieved and performance may be improved.
FIGS. 3A and 3B depict various views of another embodiment of a magnetic read transducer 100′. FIG. 3A depicts a plan view of an exemplary embodiment of the transducer 100′. FIG. 3B depicts a side view of the transducer 100′. For clarity, FIGS. 3A and 3B are not to scale. The read transducer 100′ may be part of a read head or may be part of a merged head that also includes a write transducer. The head of which the read transducer 100′ is a part is part of a disk drive having a media, a slider and the head coupled with the slider. The transducer 100′ corresponds to the transducer 100. Consequently, analogous components are labeled similarly. For example, the transducer 100′ includes a read sensor 110 having free layers 112 and 116 separated by a nonmagnetic spacer layer 114 that are analogous to such structures in the transducer 100. Thus, the components 102, 104, 110, 112, 114 116, 155 and 160′ have a similar structure and function to the components 102, 104, 110, 112, 114 116, 155 and 160, respectively, depicted in FIGS. 2A-2C. Further, although an ABS view is not shown, the transducer 100′ may appear substantially the same from the ABS as the transducer 100. The transducer 100′ may also include structures analogous to the structures 120, 130, 140 and 150 depicted in FIGS. 2A-2C.
In the embodiment shown in FIGS. 3A-3B, the rear bias structure 160′ consists of a rear soft bias structure 160′. Thus, the coercivity of the rear bias structure 160′ is less than one hundred Oe. In some such embodiments, the coercivity of the rear soft bias structure 160′ is less than ten Oe. The rear soft bias structure 160′ may be configured such that the magnetization 162 is stable perpendicular to the ABS. For example, the rear soft bias structure 160′ may have a magnetic anisotropy such that the magnetization 162 is stable during operation of the magnetic read transducer 100′. For example, a shape anisotropy may be used to stabilize the magnetization 162. In some embodiments, the length, l, of the rear soft bias structure 160′ may be much greater than the width, w, or height, t. In the embodiment shown, the height, t, of the rear soft bias structure 160′ is shown as the same as that of the read sensor 110. However, the heights may differ. However, the width of the rear soft bias structure 160′ is substantially the same as the track width of the sensor 110 (TW=w to within processing limitations). In some embodiments the length is at least four times the width (l≧4w). In some such embodiments, the length is at least ten multiplied by the width (l≧10w).
The magnetic transducer 100′ shares the benefits of the magnetic transducer 100. Performance and biasing of the sensor 110 may thus be improved.
FIGS. 4A and 4B depict various views of another embodiment of a magnetic read transducer 100′′. FIG. 4A depicts a plan view of an exemplary embodiment of the transducer 100′′. FIG. 4B depicts a side view of the transducer 100′′. For clarity, FIGS. 4A and 4B are not to scale. The read transducer 100′′ may be part of a read head or may be part of a merged head that also includes a write transducer. The head of which the read transducer 100′′ is a part is part of a disk drive having a media, a slider and the head coupled with the slider. The transducer 100′′ corresponds to the transducer 100. Consequently, analogous components are labeled similarly. For example, the transducer 100′′ includes a read sensor 110 having free layers 112 and 116 separated by a nonmagnetic spacer layer 114 that are analogous to such structures in the transducer 100. Thus, the components 102, 104, 110, 112, 114 116, 155 and 160′′ have a similar structure and function to the components 102, 104, 110, 112, 114 116, 155 and 160, respectively, depicted in FIGS. 2A-2C. Further, although an ABS view is not shown, the transducer 100′′ may appear substantially the same from the ABS as the transducer 100/100′. The transducer 100′′ may also include structures analogous to the structures 120, 130, 140 and 150 depicted in FIGS. 2A-2C.
In the embodiment shown in FIGS. 4A-4B, the rear bias structure 160′′ consists of a rear hard bias structure 160′′. Thus, the coercivity of the rear bias structure 160′ is greater than one hundred Oe. In some such embodiments, the coercivity of the rear hard bias structure 160′′ is greater than one thousand Oe. The rear hard bias structure 160′′ may be configured such that the magnetization 162′′ is stable perpendicular to the ABS. For example, the rear hard bias structure 160′′ may have an anisotropy such that the magnetization 162′′ is stable during operation of the magnetic read transducer 100′′. For example, a shape anisotropy may be used to stabilize the magnetization 162′′. In some embodiments, the length, l, of the rear hard bias structure 160′′ may be much greater than the width, w, or height, t. In the embodiment shown, the height, t, of the rear hard bias structure 160′′ is shown as the same as that of the read sensor 110. However, the heights may differ. However, the width of the rear hard bias structure 160′′ is substantially the same as the track width of the sensor 110 (TW=w to within processing limitations). In some embodiments the length is at least four times the width (l≧4w). In some such embodiments, the length is at least ten multiplied by the width (l≧10w).
The magnetic transducer 100′′ shares the benefits of the magnetic transducer 100. Performance and biasing of the sensor 110 may thus be improved.
FIGS. 5A and 5B depict another embodiment of a magnetic read transducer 100′′′. FIG. 5A depicts a plan view of an exemplary embodiment of the transducer 100′′′. FIG. 5B depicts a side view of the transducer 100′′′. For clarity, FIGS. 5A and 5B are not to scale. The read transducer 100′′′ may be part of a read head or may be part of a merged head that also includes a write transducer. The head of which the read transducer 100′′′ is a part is part of a disk drive having a media, a slider and the head coupled with the slider. The transducer 100′′′ corresponds to the transducer(s) 100, 100′ and/or 100′′. Consequently, analogous components are labeled similarly. For example, the transducer 100′′′ includes a read sensor 110 having free layers 112 and 116 separated by a nonmagnetic spacer layer 114 that are analogous to such structures in the transducer(s) 100, 100′ and/or 100′′. Thus, the components 102, 104, 110, 112, 114 116, 155, 160′′′ have a similar structure and function to the components 102, 104, 110, 112, 114 116, 155, 160/160′/160′′, respectively, depicted in FIGS. 2A43B. Further, although an ABS view is not shown, the transducer 100′′′ may appear substantially the same from the ABS as the transducer 100. The transducer 100′′′ may also include structures analogous to the structures 120, 130, 140 and 150 depicted in FIGS. 2A-2C.
The rear bias structure 160′′′ includes at least a rear soft bias structure 170 and a rear hard bias structure 180. The rear soft bias structure 170 is between the rear hard bias structure 180 and the sensor 110 as well as between the rear hard bias structure 180 and the ABS. The rear hard bias structure 180 may be a hard magnetic alloy, for example having a coercivity analogous to that discussed above for structure 160′′. For example, a CoPt alloy might be used. In other embodiments, the rear bias structure 180 may be a multilayer or other structure that functions as a hard bias structure.
The rear soft bias structure 170 is a soft bias structure. Thus, the coercivity of the rear soft bias structure 170 is analogous to that of the rear bias structure 160′. Further, the rear soft bias structure 170 provides sufficient moment to bias the magnetic moments 113 and 117 of the free layers 112 and 116, respectively. For example, in some embodiments, the rear soft bias structure has a saturation magnetization-thickness product of at least one milli-emu/cm2 and not more than three milli-emu/cm2. In some such embodiments, the saturation magnetization-thickness product is not more than two milli-emu per cm2. The thickness used in the saturation magnetization-thickness product is t, the depth of the rear soft bias structure 170 in the down track direction.
The rear soft bias structure 170 has a magnetic moment 172 that biases the free layers 112 and 116 in a direction perpendicular to the bias direction from the magnetic bias structures 130 and 150. In the embodiment shown, this direction is perpendicular to the ABS. Similarly, the rear hard bias structure 180 has a magnetic moment 182 in a direction perpendicular to the ABS. Without the rear bias structure 160, the free layers 112 and 116 may be biased antiparallel. However, because the structures 130, 150 and 160 all magnetically bias the free layers 112 and 116, the free layers 112 and 116 are biased such that the magnetic moments 113 and 117 are in a scissor mode.
In some embodiments, the rear hard bias structure 180 is separated from the rear soft bias structure 170 by the nonmagnetic layer 162. The nonmagnetic layer 162 may be conductive. In some embodiments, the thickness of the nonmagnetic layer 162 in the stripe height direction is at least ten Angstroms and not more than forty Angstroms.
In the embodiment shown in FIGS. 5A-5B, the rear hard bias structure 180 and rear soft bias structure 170 have similar geometries. In particular, the thicknesses are the same. However, in other embodiments, the thicknesses may differ. In the embodiment shown, the rear soft bias structure 170 has a length, d1 in the stripe height direction, while the hard bias structure 180 has length d2 in the stripe height direction. The total length, l, of the structure has an analogous relationship to the width, w, as described above. Further, the width of the structure 160′′′ is the same as the track width of the sensor (w=TW to within processing tolerances). The rear bias structures 170 and 180 have their magnetic moments 172 and 182, respectively, perpendicular to the ABS to bias the free layers 112 and 116 into a scissor state.
The magnetic transducer 100′′′ shares the benefits of the magnetic transducer(s) 100 and/or 100′. Further, omission of the nonmagnetic layer 162 between the soft bias structure 170 and the hard bias structure 180 may improve coupling between the structures 170 and 180. Performance and biasing of the sensor 110 may thus be improved.
FIG. 6 depicts a side view of another embodiment of a magnetic read transducer 100′′′′. For clarity, FIG. 6 is not to scale. The read transducer 100′′′′ may be part of a read head or may be part of a merged head that also includes a write transducer. The head of which the read transducer 100′′′′ is a part is part of a disk drive having a media, a slider and the head coupled with the slider. The transducer 100′′′′ corresponds to the transducer(s) 100, 100′, 100′′ and/or 100′′′. Consequently, analogous components are labeled similarly. For example, the transducer 100′′′′ includes a read sensor 110 having free layers 112 and 116 separated by a nonmagnetic spacer layer 114 that are analogous to such structures in the transducer 100. Thus, the components 102, 104, 110, 112, 116, 155 and 160′′′′ have a similar structure and function to the components 102, 104, 110, 112, 116, 155 and 160/160′/160′′/160′′′, respectively, depicted in FIGS. 2A-5B. Further, although an ABS view is not shown, the transducer 100′′′′ may appear substantially the same from the ABS as the transducer 100/100′. The transducer 100′′′′ may also include structures analogous to the structures 120, 130, 140 and 150 depicted in FIGS. 2A-2C.
In the embodiment shown in FIG. 6, the rear bias structure 160′′′′ includes a rear bias layer 160′/160′′/160′′′ and pinning structure 190. The rear bias layer 160′/160′′/160′′′ may be any one of a soft magnetic bias structure, a hard magnetic bias structure and a combination of soft and hard magnetic bias structures. The rear bias layer 160′/160′′/160′′′ may be a single alloy layer, a multilayer, or another structure. The rear bias layer 160′/160′′/160′′′ also has an anisotropy, as discussed above. For example, the length, l, of the rear bias layer 160′/160′′/160′′′ may be much greater than the width or height, t. In the embodiment shown, the height, t, of the rear bias layer 160′/160′′1160′′′ is shown as the same as that of the read sensor 110. However, the heights may differ. However, the width of the rear bias layer 160′/160′′/160′′′ is the same as the track width of the sensor 110.
In addition, the rear bias structure 160′′′′ includes the pinning layer 190. In some embodiments, the pinning layer 190 is an AFM, such as IrMn. For generality the depth, d3, of the pinning structure 190 is shown different from that of the rear bias layers 160′/160′′1160′′′. However, in other embodiments, the depths may be the same. The pinning layer 190 is exchange coupled to the rear bias layer 160′/160′′/160′′′. As a result, the pinning layer 190 may aid in stabilizing the direction of the magnetic moment 162 of the rear bias layer 160′/160′′/160′′′. For example, the pinning layer 190 may assist in returning the magnetic moment 162 to the desired direction shown in FIG. 6 in the event of a reversal.
The magnetic transducer 100′′′′ shares the benefits of the magnetic transducer(s) 100, 100′, 100′′ and/or 100′′′. Performance and biasing of the sensor 110 may thus be improved.
FIG. 7 depicts a side view of another embodiment of a magnetic read transducer 100′′′′′. For clarity, FIG. 7 is not to scale. The read transducer 100′′′′′ may be part of a read head or may be part of a merged head that also includes a write transducer. The head of which the read transducer 100′′′′′ is a part is part of a disk drive having a media, a slider and the head coupled with the slider. The transducer 100 corresponds to the transducer(s) 100, 100′, 100′′, 100′′′ and/or 100′′′′. Consequently, analogous components are labeled similarly. For example, the transducer 100′′′′′ includes a read sensor 110 having free layers 112 and 116 separated by a nonmagnetic spacer layer 114 that are analogous to such structures in the transducer 100. Thus, the components 102, 104, 110, 112, 116, 155 and 160′′′′′ have a similar structure and function to the components 102, 104, 110, 112, 116, 155 and 160/160′/160′′/160′′′/160′′′′, respectively, depicted in FIGS. 2A-6. Further, although an ABS view is not shown, the transducer 100′′′′′ may appear substantially the same from the ABS as the transducer 100. The transducer 100′′′′′ may also include structures analogous to the structures 120, 130, 140 and 150 depicted in FIGS. 2A-2C.
In the embodiment shown in FIG. 7, the rear bias structure 160′′′′′ includes a rear bias layer 160′/160′′/160′′′ and pinning structure 190′. The rear bias layer 160′/160′′/160′′′ may be any one of a soft magnetic bias structure, a hard magnetic bias structure and a combination of soft and hard magnetic bias structures. The rear bias layer 160′/160′′/160′′′ may be a single alloy layer, a multilayer, or another structure. The rear bias layer 160′/160′′/160′′′ also has an anisotropy, as discussed above. For example, the length, l, of the rear bias layer 160′/160′′/160′′′ may be much greater than the width or height, t. In the embodiment shown, the height, t, of the rear bias layer 160′/160′′/160′′′ is shown as the same as that of the read sensor 110. However, the heights may differ. However, the width of the rear bias layer 160′/160′′/160′′′ is the same as the track width of the sensor 110.
In addition, the rear bias structure 160′′′′′ includes the pinning layer 190′. The pinning layer 190′ is analogous to the pinning layer 190. However, the pinning layer 190′ is below the rear bias layer 160′/160′′/160′′′. Thus, the region behind the read sensor 110 may be overmilled. In some embodiments, the pinning layer 190′ is an AFM, such as IrMn. The pinning layer 190′ is exchange coupled to the rear bias layer 160′/160′′/160′′′. Depth, l, of the pinning structure 190 is shown as the same as that of the rear bias layers 160′/160′′/160′′′. However, in other embodiments, the depths may be different. As a result, the pinning layer 190′ may aid in stabilizing the direction of the magnetic moment 162 of the rear bias layer 160′/160′′/160′′′. For example, the pinning layer 190′ may assist in returning the magnetic moment 162 to the desired direction shown in FIG. 7 in the event of a reversal.
The magnetic transducer 100′′′′′ shares the benefits of the magnetic transducer(s) 100, 100′, 100′′, 100′′′ and/or 100′′′′. Performance and biasing of the sensor 110 may thus be improved.
The magnetic transducers 100, 100′, 100′′, 100′′′, 100′′′′ and 100′′′′′ have been shown with various configurations to highlight particular features, such as differences in geometries. One of ordinary skill in the art will readily recognize that two or more of these features may be combined in various manners consistent with the method and system described herein that are not explicitly depicted in the drawings.
FIG. 8 is an exemplary embodiment of a method 200 for providing a read transducer. For simplicity, some steps may be omitted, interleaved, combined, have multiple substeps and/or performed in another order unless otherwise specified. The method 200 is described in the context of providing a magnetic recording disk drive and transducer 100. However, the method 200 may be used in fabricating the transducer 100′, 100′′, 100′′′, 100′′′′ and/or 100′′′′′. The method 200 may be used to fabricate multiple magnetic read heads at substantially the same time. The method 200 may also be used to fabricate other magnetic recording transducers. The method 200 is also described in the context of particular layers. A particular layer may include multiple materials and/or multiple sub-layers. The method 200 is described in the context of a disk drive. However, the method may be used in other applications employing a magnetoresistive and bias structures. The method 200 also may start after formation of other portions of the magnetic recording transducer.
The read sensor 110 is provided, via step 202. Step 202 may include depositing a stack of layers for the read sensor and defining the read sensor in the cross-track and stripe height directions. Further, the shield 102 and insulating layer 106 may also be provided. The rear bias structure 160 is provided, via step 204. Step 204 may be performed after the sensor 110 has been defined in at least the stripe height direction. Thus, at least part of step 204 is performed after at least part of step 202. Steps 202 and 204 also include defining the read sensor 110 and rear magnetic bias structure 160 in the track width direction such that the track width of the read sensor 110 and width of the rear magnetic bias structure 160 are the same. In some embodiments, the track width of the read sensor 110 and the width of the rear magnetic bias structure 160 are defined together.
The side bias structures 120 are provided, via step 206. Step 206 is performed after the read sensor is defined in the cross-track direction in step 202. Thus, at least part of step 202 is performed before step 204. Step 204 may include depositing the insulating layer 106, depositing the material(s) for the magnetic bias structures 130 and 170. A mill step and planarization, such as a chemical mechanical planarization (CMP) may also be performed.
Using the method 200, the transducers 100, 100′, 100′′, 100′′′, 100′′′′ and/or 100′′′′′ may be fabricated. Thus, the benefits of one or more of the transducers 100, 100′, 100′′, 100′′′, 100′′′′ and/or 100′′′′′ may be achieved. Consequently, biasing of the free layers 112 and 116 in the read sensor 110 may be improved.
FIG. 9 is an exemplary embodiment of a method 210 for providing a rear bias structure of a read transducer. For simplicity, some steps may be omitted, interleaved, combined, have multiple substeps and/or performed in another order unless otherwise specified. The method 210 is described in the context of providing a magnetic recording disk drive and transducer 100. However, the method 210 may be used in fabricating the transducer 100′, 100′′, 100′′′, 100′′′′ and/or 100′′′′′. The method 210 may be used to fabricate multiple magnetic read heads at substantially the same time. The method 210 may also be used to fabricate other magnetic recording transducers. The method 210 is also described in the context of particular layers. A particular layer may include multiple materials and/or multiple sub-layers. The method 210 is described in the context of a disk drive. However, the method may be used in other applications employing a magnetoresistive and bias structures. The method 210 also may start after formation of other portions of the magnetic recording transducer.
The read sensor stack is deposited, via step 212. Step 212 includes depositing the free layer 112, depositing the nonmagnetic layer 114 and depositing the free layer 116. The read sensor 110 is defined in the stripe height direction, via step 214. In some embodiments, step 214 occurs before the read sensor is defined in the cross-track direction. Step 214 may include masking and ion milling the read sensor stack. Thus, space may be made for the rear bias structure 160/160′/160′′/160′′′/160′′′′/160′′′′′. The insulating layer 155 is provided, via step 216. The pinning layer 190/190′ may optionally be provided, via step 218.
The rear bias structure 160 is deposited, via step 220. Step 220 may include depositing one or more layer(s) for the rear bias structure 160. Step 220 may, for example, include depositing soft magnetic layer(s), hard magnetic layer(s) or both.
The rear soft bias structure 160 and the read sensor 110 may be defined in the cross track direction, via step 222. Thus, the rear soft bias structure 160 and the read sensor 110 are self-aligned and have matching track width/width.
An insulating layer 106 may be provided, via step 224. The side bias structures 120 may then be provided, via step 226.
Thus, the magnetic transducer 100 may be fabricated. The method 220 may also be used to fabricate the transducer(s) 100′, 100′′, 100′′′, 100′′′′ and/or 100′′′′′. Thus, the benefits of one or more of the transducers 100, 100′, 100′′, 100′′′, 100′′′′ and/or 100′′′′′ may be achieved. Consequently, biasing of the free layers 112 and 116 in the read sensor 110 may be improved.

## Claims

1. A magnetic read apparatus having an air-bearing surface (ABS) comprising:
a read sensor including a first free layer, a spacer layer, and a second free layer, the spacer layer being nonmagnetic and residing between the first free layer and the second free layer, the read sensor having a rear surface opposite to the ABS, at least one side and a track width in a cross track direction parallel to the ABS; and
a rear magnetic bias structure configured to magnetically bias the read sensor in a stripe height direction perpendicular to the ABS, the read sensor being between the ABS and the rear magnetic bias structure, the rear magnetic bias structure having a width in the cross track direction and a length in the stripe height direction, the length being greater than the width, the width of the rear magnetic bias structure being substantially equal to the track width of the read sensor;
wherein the rear magnetic bias structure has a saturation magnetization-thickness product of at least one and not more than three milli-emu/cm2.

2. The magnetic read apparatus of claim 1 wherein the rear magnetic bias structure has a reversal field of at least one thousand Oersted.

3. The magnetic read apparatus of claim 2 wherein the reversal field is at least five thousand Oersted.

4. The magnetic read apparatus of claim 2 wherein the track width is not more than twenty nanometers.

5. The magnetic read apparatus of claim 2 wherein the length is at least four multiplied by the width.

6. The magnetic read apparatus of claim 5 wherein the length is at least ten multiplied by the width.

7. The magnetic read apparatus of claim 1 wherein the read sensor has a track width of not more than thirty nanometers.

8. The magnetic read apparatus of claim 1 wherein the rear magnetic bias structure includes at least one of a rear soft magnetic bias structure and a rear hard magnetic bias structure, the rear hard magnetic bias structure having a hard bias coercivity of greater than one hundred Oersted, the rear soft bias structure having a soft bias coercivity of less than one hundred Oersted, wherein the magnetic read apparatus further includes:
an insulating layer between the read sensor and the rear magnetic bias structure.

9. The magnetic read apparatus of claim 8 wherein the hard bias coercivity is greater than one thousand Oersted and the soft bias coercivity is less than ten Oersted.

10. The magnetic read apparatus of claim 8 wherein the rear magnetic bias structure includes:
a pinning layer coupled to the at least one of the rear hard bias structure and the rear soft bias structure.

11. The magnetic read apparatus of claim 1 wherein the rear magnetic bias structure is configured to magnetically bias the first free layer and the second free layer in a scissor mode, the magnetic read apparatus further including:
a side bias structure adjacent to the at least one side, the side bias structure being configured to magnetically bias the first free layer and the second free layer to be antiferromagnetically aligned.

12. A disk drive comprising:
at least one medium; and
at least one slider including at least one magnetic transducer having an air-bearing surface (ABS) configured to reside in proximity to the at least one medium during use, the at least one magnetic transducer including a read sensor and a rear magnetic bias structure, the read sensor including a first free layer, a spacer layer, and a second free layer, the spacer layer being nonmagnetic and residing between the first free layer and the second free layer, the read sensor having a rear surface opposite to the ABS, at least one side and a track width in a cross track direction parallel to the ABS, the rear magnetic bias structure being configured to provide a magnetic bias to the read sensor in a stripe height direction perpendicular to the ABS, the read sensor being between the ABS and the rear magnetic bias structure, the rear magnetic bias structure having a width in the cross track direction and a length in the stripe height direction, the length being greater than the width, the width of the rear magnetic bias structure being substantially equal to the track width of the read sensor;
wherein the rear magnetic bias structure has a saturation magnetization-thickness product of at least one and not more than three milli-emu/cm2.

13. A method for providing a magnetic read apparatus having an air-bearing surface (ABS) comprising:
providing a read sensor stack for a read sensor, the read sensor stack including a first free layer, a spacer layer, and a second free layer, the spacer layer being nonmagnetic and residing between the first free layer and the second free layer;
defining the read sensor in a stripe height direction from the read sensor stack such that the read sensor has a rear surface opposite to the ABS;
depositing a rear magnetic bias structure stack for a rear magnetic bias structure after the step of defining the read sensor in the stripe height direction, the rear magnetic bias structure configured to magnetically bias the read sensor in the stripe height direction, the read sensor being between the ABS and the rear magnetic bias structure; and
defining a track width of the read sensor in a cross track direction and a width of the rear magnetic bias structure the cross track direction, the cross track direction being parallel to the ABS, the width of the rear magnetic bias structure being substantially equal to the track width of the read sensor;
wherein the rear magnetic bias structure has a saturation magnetization-thickness product of at least one and not more than three milli-emu/cm2.

14. The method of claim 13 wherein the step of defining the track width and the width further includes:
providing a mask covering a portion of the read sensor stack and a portion of the rear magnetic bias structure stack; and
performing an ion mill, the ion mill removing an exposed portion of the read sensor stack and an exposed portion of the rear magnetic bias structure stack.

15. The method of claim 13 wherein the rear magnetic bias structure has a reversal field of at least one thousand Oersted.

16. The method of claim 13 wherein the read sensor has a track width of not more than thirty nanometers.

17. The method of claim 13 wherein the rear magnetic bias structure includes at least one of a rear soft magnetic bias structure and a rear hard magnetic bias structure, the rear hard magnetic bias structure having a hard bias coercivity of greater than one hundred Oersted, the rear soft bias structure having a soft bias coercivity of less than one hundred Oersted.

18. The method of claim 17 further comprising:
providing a pinning layer coupled to the at least one of the rear hard bias structure and the rear soft bias structure.

19. The method of claim 13 wherein the length is at least four multiplied by the width.