Method and system for fabricating magnetic transducers with improved pinning

A method and system for providing a magnetic transducer are disclosed. The method and system include providing a magnetic element that includes a free layer, a pinned layer, and a nonmagnetic spacer layer between the free layer and the pinned layer. The nonmagnetic spacer layer is a tunneling barrier layer. The free layer is configured to be biased in a first direction. The pinned layer has a pinned layer magnetization configured to be pinned in a second direction that is at a first angle from perpendicular to the ABS. The first angle is nonzero and different from ninety degrees. The second direction and the first direction form a second angle that is different from ninety degrees.

BACKGROUND

FIG. 1depicts a portion of a conventional read transducer50from the air-bearing surface (ABS) and from above. The conventional transducer50is a read transducer that includes a read sensor52and hard bias structures64. The read sensor includes an AFM layer54, a pinned layer that is a synthetic antiferromagnetic (SAF) layer56, a nonmagnetic spacer layer58, a free layer60, and a capping layer62. The SAF56includes a ferromagnetic layer (pinned layer) adjoining the AFM54, a ferromagnetic (reference) layer and a nonmagnetic spacer layer between the pinned and reference layers. For simplicity, the pinned and reference layers are not separately depicted inFIG. 1. However, the magnetizations55and57of the pinned and reference layers, respectively, are separately shown. The magnetizations55and57are pinned perpendicular to the ABS (into or out of the plane of the page in the ABS view). The free layer60has a magnetization61biased by the magnetizations65of the hard bias structures64. For clarity, the orientation53of the AFM layer54is also shown.

In operation, the read sensor52is exposed to an external magnetic field, for example from recording media (not shown). The external magnetic field may cause the free layer magnetization61to change direction. The free layer magnetization61would thus no longer be parallel to the hard bias magnetizations65. As a result, the angle between the reference layer magnetization57(P2) and the free layer magnetization61changes. For low TMR, to a first approximation, the conductance of the read sensor52varies with the cosine of the angle between the magnetizations57and61. More specifically, if θ is the angle between the reference layer magnetization57and the free layer magnetization61, the conductance varies with 1+½*TMR*cos θ, where TMR is the maximum tunneling magnetoresistance. Thus, to a first approximation, the resistance of the sensor52varies as 1/[1+TMR*cos θ/(2+TMR)].

Although the conventional read transducer50may function, there are drawbacks. It has been determined that for higher TMR, the response of a magnetic element such as the sensor52changes. In particular, first approximation for the transfer curve of such a magnetic element as varying with case is inaccurate. Accordingly, what is needed is an improved magnetic element that may be used as the read sensor52.

SUMMARY

A method and system for providing a magnetic transducer are disclosed. The method and system include providing a magnetic element that includes a free layer, a pinned layer, and a nonmagnetic spacer layer between the free layer and the pinned layer. The nonmagnetic spacer layer is a tunneling barrier layer. The free layer is configured to be biased in a first direction. The pinned layer has a pinned layer magnetization configured to be pinned in a second direction that is at a first angle from perpendicular to the ABS. The first angle is nonzero and different from ninety degrees. The second direction and the first direction form a second angle that is different from ninety degrees.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As discussed above, the transfer curve of a magnetic element such as a conventional MR sensor52may change at higher TMR. It has been determined that these changes may adversely affect the performance of the magnetic transducer50. In particular, the conventional read sensor52may have limited utility at higher TMR. For higher TMR, the response of the read transducer52may not be symmetric for bits having opposite magnetizations. Furthermore, the magnitude of the response may be reduced. Stated differently, the sensitivity of the conventional read transducer50may be reduced. It has been determined that these losses may be due to the changes in the transfer curve for the sensor52at higher TMR. Accordingly, an improved read transducer has been developed.

FIG. 2depicts ABS and plan views of an exemplary embodiment of a transducer100at equilibrium. For clarity,FIG. 2is not to scale. The read transducer100includes read sensor102and hard bias structures120. The read transducer100may be part of a merged head including at least one write transducer (not shown) and/or may include other read transducers. The read transducer100may also reside on a slider (not shown) and be part of a disk drive.

In the embodiment shown, the read sensor102is a current-perpendicular-to-plane (CPP) sensor. Stated differently, current is driven substantially between the top and the bottom of the read sensor102as shown in the ABS view ofFIG. 2. Consequently, insulator116resides between the read sensor102and the hard bias structures120.

The read sensor102includes at least the free layer110, nonmagnetic spacer layer108, and pinned layer106, which are shown as individual layers in the ABS view. Also shown in the ABS view is the pinning layer104, which may be an AFM layer. Also shown are seed layer101and capping layer112. In other embodiments, additional layers might be included. Although depicted as single layers, the free layer110, nonmagnetic spacer layer108, pinned layer106and pinning layer104may include substructures including but not limited to sub-layers. The free layer110has a free layer magnetization111. In the embodiment shown, the free layer magnetization111is biased by the hard bias magnetization122. However, in another embodiment, the free layer magnetization111may be biased in another manner or may be biased by a combination of the hard bias magnetization122and another feature. In the embodiment shown, the free layer magnetization111may lie within the ABS. However, as described below, in another embodiment, the free layer may not be parallel to the ABS. The nonmagnetic spacer layer108is a tunneling barrier layer. Thus, in some embodiments, the nonmagnetic spacer layer108may be a thin insulating layer.

In the embodiment shown, the pinned layer108may be a SAF. However, in another embodiment, the pinned layer108may be another type of layer. For example, the pinned layer108may be a simple layer. In such an embodiment, the magnetization of the pinned layer108may be considered to be P2107for the ensuing discussion. In the embodiment shown inFIG. 2, the pinned layer108includes ferromagnetic layers separated by a nonmagnetic spacer layer. For simplicity, these layers are not separately shown inFIG. 2. The magnetizations105and107of the ferromagnetic layers are shown in the plan view. The magnetization P1105is for the ferromagnetic layer closer to the pinning layer104. The magnetization P2107is the magnetization of the reference layer, which is closest to the free layer110. Also shown in the plan view are the free layer magnetization111, hard bias magnetizations122, and orientation103of the pinning layer104.

As can be seen inFIG. 2, the pinned layer magnetizations105and107are not oriented perpendicular to the ABS. Instead, a nonzero angle, ρ, is between the magnetization P2107and normal to the ABS. A similar angle would be made between P1105and normal to the ABS. In one embodiment, the magnitude of ρ does not exceed fifty degrees. Stated differently, in such embodiments, ρ would be not more than fifty degrees clockwise or counter clockwise from perpendicular to the ABS. In some such embodiments, ρ does not exceed thirty five degrees. In some embodiments, ρ is also at least fifteen degrees. Further, the magnetizations105and107of the pinned layer108are not perpendicular to the free layer magnetization111. Instead, P2107forms an angle, φ, with the free layer magnetization111when the transducer100is not exposed to an external field, for example from a recording media. In the embodiment shown inFIG. 2, the angle φ is greater than ninety degrees. However, in another embodiment, φ may be less than ninety degrees.

In operation, the free layer magnetization111may change in response to the magnetic field due to data recorded on a media (not shown). A change in direction of the free layer magnetization111results in a change in the equilibrium angle, φ, between the P2107and the free layer magnetization111. As a result, the resistance of the read sensor102changes. Thus, data may be read from the media.

Performance of the read sensor102may be improved, particularly for high TMR by selection of the angles φ and ρ at which the read sensor102is at equilibrium. In particular, by adjusting the angle, φ, the response of the read sensor102may be modified. The adjustment to φ may be based on one or more of the shape of the transfer curve and the TMR of the read sensor102. In the embodiment shown inFIG. 2, φ is changed by changing ρ, the angle the pinned layer magnetizations105and107make with normal to the ABS. The point on the transfer curve at which the read sensor102operates may be changed by tailoring φ. As a result, the amplitude of the signal due to a bit being read may be increased. Consequently, performance of the read transducer100may be improved. Similarly, the symmetry of the response of the read sensor102may be tailored. By adjusting the angle φ, the read sensor102may be operated in a region which is more or less symmetric in the absence of other influences on the read sensor102. For example, in some embodiments, the external magnetic fields or other factors which might influence the response of the read sensor102are at or near zero. In such embodiments, the angle φ may be selected so that the response of the read sensor102, and thus the transducer100, is symmetric for opposite magnetizations being read. In another example, the angle φ might be selected so that the response of the read sensor102itself is less symmetric. Stated differently, the read sensor102may be operated at a point in its transfer curve that is less symmetric than, for example, where φ is ninety degrees. The asymmetry due to the angle φ may be used to account for other asymmetries, for example magnetic fields due to poles (not shown) or other structures in a head of which the read transducer100is a part. Thus, by modifying the angles ρ and φ, the response of the read sensor102may be customized for use in the desired read transducer. Thus performance of the read transducer100may be improved.

FIG. 3depicts a plan view of another exemplary embodiment of a transducer100′. For clarity,FIG. 3is not to scale. The read transducer100′ may be part of a merged head including at least one write transducer (not shown) and/or may include other read transducers. The read transducer100′ may also reside on a slider (not shown) and be part of a disk drive. The read transducer100′ is analogous to the read transducer100. The read transducer includes read sensor102′ and hard bias structures120′ that are analogous to the read sensor102and hard bias structures120, respectively. Thus, the read sensor102′ would include at least a free layer, nonmagnetic spacer layer that may be a tunneling barrier layer, and pinned layer/SAF analogous to the layers110,108, and106, respectively, of the sensor102. Further, a pinning layer analogous to the pinning layer104may also be included in the read sensor102′.FIG. 3depicts the magnetizations105′ and107′ of the ferromagnetic layer closest to the pining layer and the reference layer of the pinned layer, respectively. Also shown are the free layer magnetization111′, the hard bias magnetizations122′, and the orientation103′ of the pinning layer.

As can be seen inFIG. 3, the pinned layer magnetizations105′ and107′ are neither perpendicular to the ABS nor perpendicular to the free layer magnetization111′. Instead, a nonzero angle, ρ′ is between the magnetization P2107′ and perpendicular to the ABS. A similar angle would be made between P1105′ and normal to the ABS. In one embodiment, the magnitude of ρ′ does not exceed fifty degrees. Stated differently, in such embodiments, ρ′ would be not be more than fifty degrees clockwise or counter clockwise from perpendicular to the ABS. In some such embodiments, ρ′ does not exceed thirty five degrees. In some embodiments, ρ′ is also at least fifteen degrees. P2107′ forms an angle, φ′, with the free layer magnetization111′. In the embodiment shown inFIG. 3, the angle φ′ is less than ninety degrees. Further, the angle φ′ may be considered to be negative as it is clockwise from perpendicular to the ABS, while φ is counterclockwise from perpendicular to the ABS. In operation, the read transducer100′ functions in an analogous manner to the read transducer100.

Performance of the read transducer100′ may be improved, particularly for high TMR, by selection of the angles φ′ and ρ′ at which the read sensor102′ is at equilibrium. The adjustment to φ′ may be based on one or more of the shape of the transfer curve and the TMR of the read sensor102′. In particular, by adjusting the angle, φ′, the response of the read sensor102′ may be modified in a manner analogous to described above with respect to the read transducer100. In particular, the amplitude of the signal from the read sensor102′ may be increased and the response of the read sensor102′ may be made more or less symmetric. As a result, the response of the read transducer100′ may be improved.

FIG. 4depicts ABS and plan views of another exemplary embodiment of a transducer200. For clarity,FIG. 4is not to scale. The read transducer200includes read sensor202and hard bias structures220. The read transducer200may be part of a merged head including at least one write transducer (not shown) and/or may include other read transducers. The read transducer100may also reside on a slider (not shown) and be part of a disk drive.

In the embodiment shown, the read sensor202is a CPP sensor. Stated differently, current is driven substantially between the top and the bottom of the read sensor202as shown inFIG. 4. Consequently, insulator216resides between the read sensor202and the hard bias structures220. The read transducer200and read sensor202are analogous to the read transducers100/100′ and read sensor102/102′, respectively. Thus, the read transducer200operates in an analogous manner to the read transducers100/100′.

The read transducer202includes at least the free layer210, nonmagnetic spacer layer208, and pinned layer206, which are shown as individual layers in the ABS view. Also shown in the ABS view is the pinning layer204, which may be an AFM layer. Also shown are seed layer201and capping layer212. Thus, the read transducer200and read sensor202are analogous to the read transducers100/100′ and read sensor202/202′ depicted inFIGS. 2-3. Although depicted as single layers, the free layer210, nonmagnetic spacer layer208, pinned layer206and pinning layer204may include substructures including but not limited to sub-layers. The free layer210has a free layer magnetization211. In the embodiment shown, the free layer magnetization211is biased by the hard bias magnetization222. However, in another embodiment, the free layer magnetization211may be biased in another manner or may be biased by a combination of the hard bias magnetization222and another feature. The nonmagnetic spacer layer208is a tunneling barrier layer. Thus, in some embodiments, the nonmagnetic spacer layer208may be a thin insulating layer.

In the embodiment shown, the pinned layer208may be a SAF. However, in another embodiment, the pinned layer208may be another type of layer. For example, the pinned layer208may be a simple layer. In such an embodiment, the magnetization of the pinned layer208may be considered to be P2207for the ensuing discussion. In the embodiment shown inFIG. 4, the pinned layer208includes ferromagnetic layers separated by a nonmagnetic spacer layer. For simplicity, these layers are not separately shown inFIG. 4. The magnetizations205and207of the ferromagnetic layers are shown in the plan view. The magnetization P1205is for the ferromagnetic layer closer to the pinning layer204. The magnetization P2207is the magnetization of the reference layer, which is closest to the free layer210. Also shown in the plan view are the free layer magnetization211, hard bias magnetizations222, and orientation203of the pinning layer204.

As can be seen inFIG. 4, the pinned layer magnetizations205and207are not oriented perpendicular to the ABS. Instead, a nonzero angle, ρ1, is between the magnetization P2207and perpendicular to the ABS. A similar angle would be made between P1205and normal to the ABS. In one embodiment, the magnitude of ρ1does not exceed fifty degrees. Stated differently, in such embodiments, ρ1would be not more than fifty degrees clockwise or counter clockwise from perpendicular to the ABS. In some such embodiments, ρ1does not exceed thirty five degrees. In some embodiments, ρ1is also at least fifteen degrees. Further, free layer magnetization211is not parallel to the ABS, which is different than the embodiment of the read transducer100/100′ shown inFIGS. 2-3. Instead, a component of the free layer magnetization211, and thus the hard bias magnetizations222, are perpendicular to the ABS. Stated differently, the free layer magnetization211, as well as the hard bias magnetizations222, form a nonzero angle, θ, with the ABS. Thus, the magnetizations205and207of the pinned layer208are not perpendicular to the free layer magnetization211. Instead, P2207forms an angle, φ1, with the free layer magnetization211. In the embodiment shown inFIG. 4, the angle φ1is greater than ninety degrees. However, in another embodiment, φ1may be less than ninety degrees.

Performance of the read transducer200may be improved in an analogous manner to the transducers100and100′. In particular, by adjusting the angles ρ1, θ, and thus φ1, the response of the read sensor202may be customized. The adjustment to φ1may be based on one or more of the shape of the transfer curve and the TMR of the read sensor202. In particular, the magnitude of the signal may be enhanced, the symmetry of response decreased or increased. As a result, the performance of the read transducer200may be improved.

FIG. 5depicts a plan view of another exemplary embodiment of a transducer200′. For clarity,FIG. 5is not to scale. The read transducer200′ may be part of a merged head including at least one write transducer (not shown) and/or may include other read transducers. The read transducer200′ may also reside on a slider (not shown) and be part of a disk drive. The read transducer200′ is analogous to the read transducer200. The read transducer200′ includes read sensor202′ and hard bias structures220′ that are analogous to the read sensor202and hard bias structures220, respectively. Thus, the read sensor202′ would include a free layer, nonmagnetic spacer layer that may be a tunneling barrier layer, and pinned layer/SAF analogous to the layers210,208, and206, respectively, of the sensor202. Further, a pinning layer analogous to the pinning layer204may also be included in the read sensor202′.FIG. 5depicts the magnetizations205′ and207′ of the ferromagnetic layer closest to the pining layer and the reference layer of the pinned layer, respectively. Also shown are the free layer magnetization211′, the hard bias magnetizations222′, and the orientation203′ of the pinning layer. The read transducer200′ may thus operate in an analogous manner to the read transducer200.

As can be seen inFIG. 5, the pinned layer magnetizations205′ and207′ are neither perpendicular to the ABS nor perpendicular to the free layer magnetization211′. Instead, a nonzero angle, ρ1′ is between the magnetization P2107′ and perpendicular to the ABS. A similar angle would be made between P1105′ and normal to the ABS. In one embodiment, the magnitude of ρ1′ does not exceed fifty degrees. Stated differently, in such embodiments, ρ1′ would be not more than fifty degrees clockwise or counter clockwise from perpendicular to the ABS. In some such embodiments, ρ1′ does not exceed thirty five degrees. In some embodiments, ρ1′ is also at least fifteen degrees. P2107′ forms an angle, φ1′, with the free layer magnetization111′. In the embodiment shown inFIG. 3, the angle φ1′ is less than ninety degrees. In addition, the free layer magnetization211′ does not lie within the ABS. Instead, the free layer magnetization211′ is at an angle, θ′, from the ABS.

Performance of the read transducer200′ may be improved, particularly for high TMR by selection of the angles ρ1′, θ′, and, therefore, φ1′. In particular, by adjusting the angle, φ1′, the response of the read sensor202′ may be modified in a manner analogous to described above with respect to the read transducer200. The adjustment to φ1′ may be based on one or more of the shape of the transfer curve and the TMR of the read sensor202′. In particular, the amplitude of the signal from the read sensor202′ may be improved and the response of the read sensor102′ may be made more or less symmetric. As a result, the response of the read transducer200′ may be improved.

FIGS. 6-7depict plan views of exemplary embodiments of transducers200″ and200′″. For clarity,FIGS. 6-7are not to scale. The read transducers200″ and200′″ may be part of merged heads including at least one write transducer (not shown) and/or may include other read transducers. The read transducers200″ and200′″ may also reside on a slider (not shown) and be part of a disk drive. The read transducers200″ and200′″ are analogous to the read transducer200and200′. The read transducers200″/200″ includes read sensor202″/200′″ and hard bias structures220″/220′″ that are analogous to the read sensor202/202′ and hard bias structures220/220′, respectively. However, the orientations of the free layer magnetizations211″ and211′″ differ. In particular, the free layer magnetizations211″ and211′″ are oriented away from the ABS. The read transducer200″ and200′″ operate in a manner analogous to the read transducers200and200′.

Thus, the pinned layer magnetizations205″/205′″ and207″/207′″ are neither perpendicular to the ABS nor perpendicular to the free layer magnetization211″/211′″. Instead, nonzero angles ρ1″/ρ1′″ is between the magnetization P2207″/207′″ and perpendicular to the ABS. A similar angle would be made between P1205″/205′″ and normal to the ABS. Further, there are nonzero angles, θ″/θ′″, between the ABS and the free layer magnetizations211″/211′″. In one embodiment, the magnitude of ρ1″/ρ1′″ does not exceed fifty degrees. Stated differently, in such embodiments, ρ1″/ρ1′″ would be not more than fifty degrees clockwise or counter clockwise from perpendicular to the ABS. In some such embodiments, ρ1″/ρ1′″ does not exceed thirty five degrees. In some embodiments, ρ1″/ρ1′″ is also at least fifteen degrees. P2207″/207′″ form angles, φ1″/φ1′″, with the free layer magnetization211″/211′″. In the embodiment shown inFIGS. 6-7, the angle φ1″/φ1′″ is different from ninety degrees.

Performance of the read transducers200″/200″ may be improved in an analogous manner to the transducers100,100′,200, and200′. The adjustment to φ1″/φ1′″ may be based on one or more of the shape of the transfer curve and the TMR of the read sensor202″/202″. In particular, the amplitude of the signal from the read sensor202″/202″ may be improved and the response of the read sensor202″/202″ may be made more or less symmetric. As a result, the response of the read transducer200″/200″ may be improved.

FIG. 8is a flow chart depicting an exemplary embodiment of a method300for fabricating a magnetic transducer. For simplicity, some steps may be omitted or combined. For clarity, the method300is described in the context of the transducers100and200. However, the method may be used to fabricate other transducers including but not limited to the transducers100′,200′,200″, and200′″. Although described in the context of forming single transducers, the method300may be used to form multiple transducers.

A magnetic element102/202is provided, via step302. The magnetic element includes at least one free layer110/210, a pinned layer106/206, and a nonmagnetic spacer layer108/208between the free layer110/210and the pinned layer106/206. The free layer magnetization111/211is configured to be biased in a first direction, for example by hard bias structures120/220. The pinned layer106/206has a pinned layer magnetization107/207and/or105/205. Step302may include providing a SAF for the pinned layer, as well as providing a pinning layer. In some embodiments, step302may include blanket depositing the layers for the read sensors102/202and defining the read sensors102/202from these layers. In some embodiments, other structures, such as the hard bias structures120/220may also be provided.

The pinned layer magnetization107/207and/or105/205is biased, via step304. The pinned layer106/206is biased such that the magnetization105or107/205or207forms an angle ρ/ρ1with perpendicular to the ABS and such that the magnetization105or107/205or207and the free layer magnetization111/211are not perpendicular. In some embodiments, step304is performed such that ρ/ρ1is not more than fifty degrees. In some embodiments, ρ/ρ1is at least fifteen degrees and not more than thirty-five degrees. In some embodiments, step304includes not only biasing the pinned layer magnetization105or107/205or207such that they are not perpendicular to the ABS. In some embodiments, the free layer magnetizations111/211are also biased so that they do not lie within the ABS.

Using the method300, the transducer(s)100and/or200may be provided. Similarly, the method300may also be used to form transducer(s)100′,200′,200″, and or other transducers. Thus, read transducers having improved signal amplitude and symmetry may be fabricated.

FIG. 9is a flow chart depicting an exemplary embodiment of another method310for fabricating a magnetic transducer. For simplicity, some steps may be omitted or combined. For clarity, the method310is described in the context of the transducers100and200. However, the method may be used to fabricate other transducers including but not limited to the transducers100′,200′,200″, and200′″. Although described in the context of forming single transducers, the method300may be used to form multiple transducers.

A magnetic element102/202is provided, via step312. The magnetic element includes at least one free layer110/210, a pinned layer106/206, and a nonmagnetic spacer layer108/208between the free layer110/210and the pinned layer106/206. The free layer magnetization111/211is configured to be biased in a first direction, for example by hard bias structures120/220. The pinned layer106/206has a pinned layer magnetization107/207and/or105/205. Step312may include providing a SAF for the pinned layer, as well as providing a pinning layer. In some embodiments, step312may include blanket depositing the layers for the read sensors102/202and defining the read sensors102/202from these layers.

The hard bias structures120/220may be provided, via step314. Step314may include blanket depositing the seed and other layers for the hard bias structures120/220, then defining the hard bias structures120/220from these layers.

The transducer100/200is annealed in a sufficiently high magnetic field and at a sufficiently high temperature to pin the magnetizations105/107and205/207, via step316. The pinned layer106/206is thus biased such that the magnetization105or107/205or207forms an angle ρ/ρ1with perpendicular to the ABS. In some embodiments, step316is performed such that ρ/ρ1is not more than fifty degrees. In some embodiments, ρ/ρ1is at least fifteen degrees and not more than thirty-five degrees. In some embodiments, step316thus includes biasing the pinned layer magnetization105or107/205or207such that they are not perpendicular to the ABS.

The hard bias magnetizations122/222are set in the desired direction(s), via step318. Step318may thus include applying a sufficiently high magnetic field in the desired direction for the free layer magnetization111/211. In some embodiments, the free layer magnetizations211are also biased so that they do not lie within the ABS. Thus, using the step316and318, the desired angle φ/φ1between the free layer magnetization111/211and the pinned layer magnetizations107/207may be obtained. Fabrication of the transducer100/200may then be completed.

Using the method310, the transducer(s)100and/or200may be provided. Similarly, the method310may also be used to form transducer(s)100′,200′,200″, and or other transducers. Thus, read transducers having improved signal amplitude and symmetry may be fabricated.