Method for providing an improved AFM reader shield

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional U.S. Patent Application Ser. No. 61/818,389, filed on May 1, 2013, which is hereby incorporated by reference in its entirety.

BACKGROUND

FIG. 1 depicts an air-bearing surface (ABS) view of a conventional read transducer 10. The conventional read transducer 10 includes shields 12 and 20, sensor 14 and magnetic bias structures 16. The read sensor 14 is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor. The read sensor 14 includes an antiferromagnetic (AFM) layer, a pinned layer, a nonmagnetic spacer layer, and a free layer. Also shown is a capping layer. In addition, seed layer(s) may be used. The free layer has a magnetization sensitive to an external magnetic field. Thus, the free layer functions as a sensor layer for the magnetoresistive sensor 14. The magnetic bias structures 16 may be hard bias structures or soft bias structures 16. These magnetic bias structures are used to magnetically bias the sensor layer of the sensor 14.

Although the conventional transducer 10 functions, there are drawbacks. In particular, the magnetic moment of the shield 20 may be unstable. For example, there may be multiple magnetic domains within the shield 20. Movement of domain walls and other changes to the magnetic moment of the shield 20 may introduce noise or otherwise adversely affect performance of the conventional read transducer 10.

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 a conventional read transducer.

FIG. 2 depicts an ABS view of an exemplary embodiment of a magnetic recording read transducer.

FIG. 3 is flow chart depicting an exemplary embodiment of a method for fabricating a magnetic recording read transducer.

FIG. 4 depicts a plan view of an exemplary embodiment of magnetic recording transducers during fabrication.

FIG. 5 depicts a plan view of another exemplary embodiment of magnetic recording transducers during fabrication.

FIG. 6 depicts an ABS view of another exemplary embodiment of a portion of a shield in a magnetic recording read transducer.

FIG. 7 is flow chart depicting an exemplary embodiment of a method for fabricating a shield in a magnetic recording read transducer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 depicts an ABS view of a portion of an exemplary embodiment of a magnetic read transducer 50. For clarity, FIG. 2 is not to scale. The read transducer 50 may be part of a read head or may be part of a merged head that also includes a write transducer. The transducer 50 includes shields 52 and 60, a read sensor 54, and magnetic bias structures 58. The sensor 54 shown is a GMR or TMR sensor. Thus, the sensor 54 includes a sensor pinning layer 51 that may be an AFM layer, a pinned layer 53, a nonmagnetic spacer layer 55, a free layer 57, and a capping layer (not labeled in FIG. 2). The sensor 54 may also include seed layer(s) (not shown). An AFM layer 51 is used to pin the magnetic moment of the pinned layer 53 in a direction. This pinning direction may be set by annealing the sensor 54 in a magnetic field oriented in the desired, sensor pinning, direction. In other embodiments, the pinning layer 51 may be omitted or may use a different pinning mechanism. The pinned layer 53 and free layer 57 are each shown as a single layer, but may include multiple layers including but not limited to a synthetic antiferromagnetic (SAF) structure. The nonmagnetic spacer layer 55 may be a conductive layer, a tunneling barrier layer, or other analogous layer. Although depicted as a GMR or TMR sensor, in other embodiments, other structures and other sensing mechanisms may be used for the sensor.

The magnetic bias structures 58 may be soft bias structures fabricated with soft magnetic material(s). In such an embodiment, the soft magnetic bias structures 58 have a high permeability and a coercivity of less than ten Oe. In some such embodiments, the soft magnetic bias structures 58 have a coercivity of not more than five Oe. For example, the soft magnetic bias structures 58 may include NiFe, such as Permalloy. In other embodiments, the magnetic bias structures 58 may be hard magnetic bias structures. In such embodiments, the hard magnetic bias structures would have their magnetic moment set perpendicular to the sensor pinning direction. Because the soft magnetic bias structures 56 have a magnetic moment, the soft magnetic bias structures 56 magnetically bias the free layer.

The magnetic read transducer 50 also includes an antiparallel coupled second shield 60. The shield 60 includes ferromagnetic layers 62 and 66, nonmagnetic spacer layer 64, and pinning layer 68. The shield 60 may also include a capping layer 70. The ferromagnetic layers 62 and 66 are separated by nonmagnetic spacer layer 64. The nonmagnetic spacer layer 64 may be Ru, which allows the magnetic moments of the layers 62 and 66 to be coupled antiparallel. The nonmagnetic spacer layer 64 may have a thickness of at least four Angstroms and not more than ten Angstroms. If such a Ru layer is used, the ferromagnetic layers 62 and 66 may be antiferromagnetically coupled via an RKKY interaction. In other embodiments, another coupling mechanism may be used. The ferromagnetic layers 62 and 66 may each be a simple layer or a multilayer. For example, the ferromagnetic layer 62 may include a NiFe layer and CoFe layer. The ferromagnetic layer 66 may include a CoFe layer and a NiFe layer. In other embodiments the ferromagnetic layer 66 may include two CoFe layers that sandwich a NiFe layer The NiFe is a soft magnetic material. The moment of the ferromagnetic layer 66 is pinned by the pinning layer 68. The pinning layer 68 is typically an antiferromagnet (AFM), such as IrMn.

FIG. 3 is an exemplary embodiment of a method 100 for providing a read transducer including an antiparallel coupled shield. For simplicity, some steps may be omitted, interleaved, and/or combined. The method 100 is also described in the context of providing a single recording transducer 50 and shield 60 depicted in FIG. 2. However, the method 100 may be used to fabricate multiple transducers at substantially the same time. The method 100 may also be used to fabricate other shields including but not limited to the shield 60. The method 100 is also described in the context of particular layers. A particular layer may include multiple materials and/or multiple sub-layers. The method 100 also may start after formation of other portions of the magnetic recording transducer.

Referring to FIGS. 2-3, the first shield 52 is provided, via step 102. Step 102 typically includes depositing a large high permeability layer. The sensor 54 is provided, via step 104. Step 104 typically includes depositing the layers for the sensor 54, then defining the sensor 54 in at least the track width direction using an ion mill. In some embodiments, the free layer 57 and pinned layer 53 of the sensor 54 are also defined in the stripe height direction. The direction in which the magnetic moment of the pinned layer 53 is pinned is also set in step 104. This direction is termed herein the sensor pinning direction. Step 104 may include annealing the sensor 54 in the presence of a magnetic field oriented in the direction in which the magnetic moment of the pinned layer 53.

The magnetic bias structures 58 may optionally be provided, via step 106. The magnetic bias structures 58 may be soft magnetic bias structures. Step 106 may thus include depositing the high permeability and any other material(s) for the magnetic bias structures 58 and defining the magnetic bias structures 58 in the track width and stripe height direction. In some embodiments, portions of steps 104 and 106 are interleaved. For example, portions of the sensor 54 may be defined in the stripe height direction as the soft magnetic bias structures are defined in the stripe height direction. Step 106 may also include depositing multiple layers for the soft magnetic bias structures 58. Further, in some embodiments, the soft magnetic bias structures 58 are provided such that they may be magnetically coupled to the shield 52 and/or 60. In other embodiments, step 106 may form hard bias structures. In such embodiments, the hard bias materials, which have a coercivity higher than that used in reading or writing, are deposited. In addition, a field may be applied to set the magnetization direction for the hard bias structures 58. In such embodiments, the hard bias magnetic field applied in step 106 is generally perpendicular to the sensor pinning direction of step 104. Thus, the hard bias pinning direction is also perpendicular to the sensor pinning direction.

The shield 60 is provided in step 108. In some embodiments, the substeps of step 108 are performed as a single processing block in a single deposition system. Thus, the ferromagnetic layers 62 and 66, nonmagnetic layer 64, pinning layer 68 and capping layer 70 are provided, via step 108. Step 108 includes depositing one or more of the layers 62, 66 and 68 in a magnetic field. These deposition magnetic fields may be oriented such that is it neither orthogonal to nor parallel to the sensor pinning direction. In some embodiments, all of the magnetic layers 62, 66 and 68 are deposited in field(s) oriented in the same direction. In some embodiments, the magnitude of the deposition magnetic field(s) for the layers 62 and 66 are also the same. In other words, the same deposition magnetic field may be used for each of the layers 62 and 66. Typically, the magnitude of the magnetic field for the layer 68 is lower than that used for the layers 62 and 66. In some embodiments, the deposition field is oriented at least forty-five degrees and not more than seventy degrees from the sensor pinning direction. In some such embodiments, the deposition field is at least fifty degrees and not more than sixty degrees from the sensor pinning direction. If a hard bias structure is used for magnetic bias structures 58, then the direction of the magnetic field used in step 108 may be between the sensor pinning direction and the hard bias magnetic field direction. However, in another embodiment, the deposition and/or annealing fields may be oriented in another direction.

In some embodiments, step 108 also includes annealing the second shield 60 in a magnetic field. This annealing magnetic field in step 108 may be oriented in the same direction as the deposition magnetic field for one or more of the layers 62, 66 and 68. However, the annealing magnetic field generally has a significantly larger magnitude than the deposition magnetic field. The annealing may be at a temperature of at least two hundred degrees and not more than two hundred and fifty degrees centigrade for a time of at least fifteen minutes and not more than two hours. In some embodiments, the anneal is at a temperature of at least two hundred twenty degrees and not more than two hundred thirty degrees centigrade for at least thirty minutes and not more than one hour. However, in other embodiments, other anneal times and/or temperatures may be used.

The orientations of the fields and pinning directions may be understood with reference to FIGS. 4-5. For example, FIG. 4 depicts an exemplary embodiment of a substrate 120 on which one or more magnetic transducers 50 may be fabricated. For simplicity, individual transducers 50 are not shown. For clarity, FIG. 4 is not to scale. FIG. 4 depicts the relevant directions of magnetic field(s) and/or pinning directions. Referring to FIGS. 2-4, the arrow 122 depicts the sensor pinning direction. Thus, the magnetic field used in step 104 is oriented along the arrow 122. As such, the arrow 122 is also the direction in which the magnetic moment of the pinned layer 53 is oriented and is referred to hereafter as the sensor pinning direction. The sensor pinning direction 122 thus indicates the direction of the magnetic field that provides the read sensor 54 and sets the direction of magnetization of the pinned layer 53. The dashed line indicates a direction perpendicular to the sensor pinning direction 122. The arrow 124 depicts the direction at which the deposition magnetic field(s) are oriented. These fields are at an angle, β, from the sensor pinning direction 122. This angle, β, neither zero nor ninety degrees. Although β is shown as being measured clockwise from the pinning direction 122, in other embodiments, β may be counterclockwise from the pinning direction 122. Further, the arrow 124 may also indicate the direction at which the shield 60 is annealed. Thus, the deposition magnetic field(s) and the annealing magnetic field(s) may oriented along the arrow 124.

FIG. 5 depicts another exemplary embodiment of a substrate 120′ on which one or more magnetic transducers 50 may be fabricated. For simplicity, individual transducers 50 are not shown. For clarity, FIG. 5 is not to scale. The components shown in FIG. 5 are analogous to those shown in FIG. 4 and are, therefore, labeled similarly. FIG. 5 depicts the relevant directions of magnetic field(s) and/or pinning directions. Referring to FIGS. 2-3 and 5, the arrow 122 depicts the sensor pinning direction, described above. The arrow 124 depicts the direction at which the deposition magnetic field(s) are oriented. These fields are at an angle, β, from the sensor pinning direction 122. This angle, β, neither zero nor ninety degrees. Although β is shown as being measured counterclockwise from the pinning direction 122, in other embodiments, β may be clockwise from the pinning direction 122. Further, the arrow 124 may also indicate the direction at which the shield 60 is annealed. Thus, the deposition magnetic field(s) and the annealing magnetic field(s) may oriented along the arrow 124.

In addition, in the embodiment shown in FIG. 5, the bias structures 58 are hard bias structures. The arrow 126 thus depicts the direction at which the magnetic moments of the hard bias structures 58 are oriented. The arrow 126 is thus termed the hard bias pinning direction 126. In the embodiment shown, the arrow 124 is between the sensor pinning direction 122 and the hard bias pinning direction 126. In other words, the deposition magnetic field(s) are oriented in a direction between the sensor pinning direction 122 and the hard bias pinning direction 126. Similarly, the annealing magnetic field for the shield 60 may be oriented in a direction between the sensor pinning direction 122 and the hard bias pinning direction 126. However, in other embodiments, the deposition magnetic field(s) and/or the annealing magnetic field(s) may be oriented in another direction.

The method 100 may result in improved performance of the magnetic transducer 50. Because the magnetic transducer 50 has an antiferromagnetically coupled second shield 60, the performance of the magnetic transducer 50 may be improved. More specifically, noise that may adversely affect the performance of a conventional magnetic transducer may be reduced or eliminated. Further, the stability of the antiferromagnetically coupled shield 60 may be enhanced. Deposition of the magnetic layers 62, 66 and/or 68 in a field as described above in conjunction with annealing the shield 60 in a field having the same direction may result in the magnetic moments of the layers 62 and 66 being more stably pinned. For example, there may be little or no change in the easy axes of the layers 62 and 66 at working temperatures of the magnetic transducer 50. The characteristics of the magnetic transducer 50 may be more stable. Thus, performance of the transducer 50 may be enhanced.

FIG. 4 is an exemplary embodiment of a portion of a shield 150. For clarity, FIG. 4 is not to scale. The shield 150 is analogous to the shield 60. However, the shield 140 includes multiple layers and/or materials rather than single monolithic layers, but may still be formed using the method 100. Referring to FIGS. 2-6, the shield 150 includes two ferromagnetic layers 160 and 180 separated by a nonmagnetic spacer layer 170. The ferromagnetic layers 160 and 180 may be magnetically soft. The ferromagnetic layers 160 and 180 are also coupled antiparallel through the nonmagnetic spacer layer 170, for example via an RKKY coupling. In some embodiments, therefore, the nonmagnetic spacer layer 170 may be Ru. The shield 150 may also include a pinning layer 190, such as an AFM layer, that pins the magnetic moment of the ferromagnetic layer 180. In some embodiments, the pinning layer 190 includes at least sixty and not more than three hundred Angstroms of IrMn. Thus, one ferromagnetic layer 160 may be adjacent to the magnetic bias structures 58 and sensor 54, while the other ferromagnetic layer 180 is adjacent to the pinning layer 190. In the embodiment shown, the ferromagnetic layer 180 is a soft magnetic layer.

The bottom ferromagnetic layer 160 includes two ferromagnetic layers 162 and 164 that are ferromagnetically coupled. In other embodiments, the ferromagnetic layer 160 may include another number of layers. Further, although depicted and described as separate layers, layers 162 and 164 may just be two portions 162 and 164 of the layer 160. For example, there may be no clear interface between the layers 162 and 164, simply change(s) in concentrations and/or types of constituents. The ferromagnetic layer 162 is a soft magnetic layer. For example, the ferromagnetic layer 162 may be a NiFe layer 162. The ferromagnetic layer 162 is also generally significantly thicker than the layer 164. In some embodiments, for example, the ferromagnetic layer 162 may be at least two hundred Angstroms thick, while the layer 164 is not more than thirty Angstroms thick. In other embodiments, the thicknesses of the layers 162 and 164 may vary.

The other ferromagnetic layer 164 is a CoFe layer. The CoFe layer 164 may include at least twenty-five atomic percent and not more than fifty atomic percent Fe. In other words, the layer 164 is Co_1-xFe_x, where x is at least 0.25 and not more than 0.5. In some embodiments, the CoFe layer 164 includes at least thirty-five percent and not more than forty atomic percent Fe. However, other stoichiometries may be used in other embodiments. The layer 164 may also be thin. For example, the layer 164 may be not more than twenty Angstroms thick. In some embodiments, the layer 164 is not more than ten Angstroms thick. As described with respect to step 108 of the method 100, the ferromagnetic layer 160 may be deposited in a magnetic field oriented in a direction 124 at an angle, β, from the sensor pinning direction 122. Thus, the layers 162 and 164 may be deposited in the deposition magnetic field in the direction 124.

The ferromagnetic layer 180 is depicted as including layers 182, 184 and 186 that are ferromagnetically coupled. In other embodiments, the ferromagnetic layer 180 may include some combination of one or more of the layers 182, 184 and 186. In other embodiments, the ferromagnetic layer 180 may include another number of layers. The ferromagnetic layer 184 is a soft magnetic layer and may be a NiFe layer. The ferromagnetic layer 184 is also generally significantly thicker than the layer 182 or 186. In some embodiments, for example, the ferromagnetic layer 184 may be at least two hundred Angstroms thick, while the layers 182 and 186 may each be not more than thirty Angstroms thick. In some embodiments, the layers 182 and 186 may each be not more than twenty Angstroms thick. In some embodiments, the layers 182 and 186 are each not more than ten Angstroms thick. In other embodiments, the thicknesses of the layers 182, 184 and 186 may vary. The ferromagnetic layers 182 and 186 may each be a CoFe layer. The CoFe layers 182 and 186 may each includes at least twenty-five atomic percent and not more than fifty atomic percent Fe. In some embodiments, each of the CoFe layers 182 and 186 includes at least thirty-five percent and not more than forty atomic percent Fe. However, other stoichiometries are possible. As described with respect to step 108 of the method 100, the ferromagnetic layer 180 may be deposited in a magnetic field oriented in a direction 124 at an angle, β, from the sensor pinning direction 122. Thus, the layers 182, 184 and 184 may be deposited in the deposition magnetic field in the direction 124. Further, as discussed above for the method 100, the shield 150 may be annealed in a magnetic field along the direction 124.

Use of the method 100 in fabricating the shield 150 may result in the magnetic moments of the layers 162, 164, 182, 184 and 186 being more stable. Performance and stability of the magnetic shield 150, and thus the transducer 50, may be improved. Because of the presence of the CoFe layers 182 and 164, the coupling between the layers 160 and 180 may be enhanced. The saturation field, H_sat, may also be increased. In addition, peaks in the oscillations in the RKKY interaction between the layers 180 and 160 may be broadened. Thus, the antiferromagnetic coupling between the layers 160 and 180 may be less sensitive to the thickness of the layer 170. The margin for processing of the shield 150 may thus be increased. Performance of the shield 150 and, therefore, the magnetic recording transducer 50 may be enhanced. Further, the layer 180 has the CoFe layer 186 adjacent to the antiferromagnetic layer 190. In such embodiments, the exchange coupling between the ferromagnetic layer 180 and the AFM layer 190 is enhanced. Performance of the shield 150 and the magnetic recording transducer 50 may be further improved.

FIG. 7 is an exemplary embodiment of a method 200 for providing a shield having antiferromagnetically coupled layers, such as the shield(s) 60 and/or 150. For simplicity, some steps may be omitted, interleaved, and/or combined. The method 200 is also described in the context of providing a single shield 60/150 in a magnetic recording transducer 50 depicted in FIGS. 2 and 6. However, the method 200 may be used to fabricate multiple shields in multiple at substantially the same time. The method 200 may also be used to fabricate other shields. 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 also may start after formation of other portions of the magnetic recording transducer.

Referring to FIGS. 2 and 4-7, the first ferromagnetic layer 62/160 is deposited in a magnetic field aligned in a particular direction 124, via step 202. This field is in a direction 124 at a nonzero, nonorthogonal angle, β, from the sensor pinning direction 122. Step 202 may include depositing multiple layers 162 and 164 in the magnetic field.

The nonmagnetic spacer layer 64/170 is deposited, via step 204. This step may or may not be performed in the presence of a magnetic field. In some embodiments, step 204 includes depositing a Ru layer having a thickness of at least four and not more than ten Angstroms.

The ferromagnetic layer 66/180 is deposited in a magnetic aligned in a particular direction 124, via step 206. This field is in a direction 124 at a nonzero, nonorthogonal angle, β, from the sensor pinning direction 122. Thus, the magnetic fields used in steps 202 and 206 are aligned. In some embodiments, the same magnetic field is used in steps 202 and 206. Step 202 may include depositing multiple layers 182, 184 and 186 in the magnetic field.

The pinning layer 68/190 is deposited in a magnetic aligned in a particular direction 124, via step 208. This field is in a direction 124 at a nonzero, nonorthogonal angle, β, from the sensor pinning direction 122. Thus, the magnetic fields used in steps 202, 206 and 208 are aligned. In some embodiments, the same magnetic field is used in steps 202, 206 and 208.

The shield 60/150 is annealed in a field, via step 210. This annealing field is in a direction 124 at a nonzero, nonorthogonal angle, β, from the sensor pinning direction 122. Thus, the magnetic fields used in steps 202, 206, 208 and 210 are aligned. Note, however, that the magnitude of the magnetic field used in step 210 is generally greater than the magnitude of the field(s) used in steps 202, 206 and 208.

A more stable shield 60 and/or 150 may be provided using the method 200. Thus, the benefits of the shield 60 and/or 150 may be achieved.