Magnetic element with reduced shield-to-shield spacing

A magnetic stack is disclosed. The magnetic stack includes a magnetically responsive lamination that includes a ferromagnetic free layer, a synthetic antiferromagnetic (SAF) structure, and a spacer layer positioned between the ferromagnetic free layer and the SAF structure. The magnetically responsive lamination is separated from a sensed data bit stored in an adjacent medium by an air bearing surface (ABS). The stack also includes a first antiferromagnetic (AFM) structure coupled to the SAF structure a predetermined offset distance from the ABS, and a second AFM structure that is separated from the first AFM structure by a first shield layer.

SUMMARY

In one aspect, the present disclosure provides a magnetic stack that includes a magnetically responsive lamination. The magnetically responsive lamination includes a ferromagnetic free layer, a synthetic antiferromagnetic (SAF) structure, and a spacer layer positioned between the ferromagnetic free layer and the SAF structure, where the magnetically responsive lamination is separated from a sensed data bit stored in an adjacent medium by an air bearing surface (ABS). The stack further includes a first antiferromagnetic (AFM) structure coupled to the SAF structure a predetermined offset distance from the ABS, and a second AFM structure separated from the first AFM structure by a first shield layer.

In another aspect, the present disclosure provides a method of forming a magnetic stack. The method includes forming a shield layer; forming an AFM structure proximate the shield layer; and forming an SAF structure proximate the AFM structure, where the SAF structure includes a pinned layer proximate the AFM structure and coupled to the AFM structure. The method further includes selectively removing a portion of the pinned layer and AFM structure in a region of the magnetic stack to expose a portion of the shield layer proximate the region; and depositing shield material in the region of the magnetic stack, where the shield material is coupled to the shield layer. The method further includes depositing pinned layer material on the shield material proximate the pinned layer; and forming a magnetically responsive lamination proximate the SAF structure.

In another aspect, the present disclosure provides a magnetic stack that includes a magnetically responsive lamination. The magnetically responsive lamination includes a ferromagnetic free layer, an SAF structure, and a spacer layer positioned between the ferromagnetic free layer and the SAF structure, where the magnetically responsive lamination is separated from a sensed data bit stored in an adjacent medium by an ABS. The stack further includes an AFM structure coupled to the SAF structure a predetermined offset distance from the ABS; and a first shield layer proximate the AFM structure such that the AFM structure is between at least a portion of the first shield layer and the SAF structure. The SAF structure includes a pinned layer that is coupled to the first shield layer.

These and other aspects of the present disclosure will be apparent from the detailed description below. In no event, however, should the above summaries be construed as limitations on the claimed subject matter, which subject matter is defined solely by the attached claims, as may be amended during prosecution.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying set of drawings that form a part hereof and in which are shown by way of illustration several specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

“Include,” “including,” or like terms means encompassing but not limited to, that is, including and not exclusive. It should be noted that “top” and “bottom” (or other terms like “upper” and “lower”) are utilized strictly for relative descriptions and do not imply any overall orientation of the article in which the described element is located.

The present disclosure generally relates to magnetic elements or stacks capable of detecting magnetic fluctuations, e.g., stacks that can be used as read sensors in data transducing heads and magnetic memory elements used to provide non-volatile storage of data. The areal density of a data storage device has become more important as data storage capacity increases. Raising the areal density of a device corresponds to smaller reading components and more data bits for a given area. A reduction in the size of a data reader, however, can lead to magnetic instability and inaccurate data sensing through the presence of noise and poor cross-track resolution.

Currently, these magnetic elements include an antiferromagnetic (AFM) structure and a synthetic antiferromagnetic (SAF) structure formed on the AFM structure. The AFM and SAF structures are coupled to each other through interfacial exchange coupling, thereby stabilizing reference layers of the sensor. The reference layers preferably maintain their magnetization in the presence of a magnetic field produced by magnetic media.

A tunnel barrier and free layer are then deposited on the reference layers. The free layer can respond to the media field. The magnitude of the tunneling conductance between the free layer and the reference layers depends on the relative direction between the magnetization in the reference layers and the free layer. The magnetic state of the magnetic media can be read based upon this change in tunneling conductance.

In at least some current designs of magnetic sensors, all of these layers typically extend to an air bearing surface (ABS). It may be beneficial for the free layer to extend to the ABS as the media's magnetic field decays with head-media spacing (HMS). An AFM structure that extends to the ABS, however, adds to the shield-to-shield spacing (SSS) and thereby increases the physical and magnetic thickness of the magnetic stack. By recessing the AFM structure from the ABS, the SSS will be reduced while the SAF structure can remained “pinned” in its magnetic state.

Accordingly, various embodiments of the present disclosure are generally directed to a magnetically responsive lamination that includes a ferromagnetic free layer, an SAF structure, and a spacer layer positioned between the ferromagnetic free layer and the SAF structure. The lamination is separated from a sensed data bit stored in an adjacent medium by an ABS. The SAF structure is coupled to an AFM structure a predetermined offset distance from the ABS. Such position of the AFM structure that is offset from an ABS can allow for a smaller shield-to-shield spacing that corresponds to increased areal density capability and accurate data sensing.

In some embodiments, the stack includes a second AFM structure separated from the first AFM structure by a shield layer. In some embodiments, the pinned layer is also coupled to a shield layer, which may further stabilize the magnetic properties of the SAF structure.

An example of a data storage device100is provided inFIG. 1. The device100shows a non-limiting environment in which various embodiments of the present disclosure can be practiced. The device100includes a substantially sealed housing102formed from a base deck104and top cover106. An internally disposed spindle motor108is configured to rotate a number of magnetic storage media110. The media110are accessed by a corresponding array of data transducers (read/write heads) that are each supported by a head gimbal assembly (HGA)112.

Each HGA112can be supported by a head-stack assembly114(“actuator”) that includes a flexible suspension116, which in turn is supported by a rigid actuator arm118. The actuator114preferably pivots about a cartridge bearing assembly120through application of current to a voice coil motor (VCM)122. In this way, controlled operation of the VCM122causes the transducers (numerically denoted at124) to align with tracks (not shown) defined on the media surfaces to store data thereto or retrieve data therefrom.

FIG. 2is a schematic cross-section view of one embodiment of a magnetic stack130capable of being used as a read sensor in the data transducers124ofFIG. 1. The stack130includes a magnetically responsive lamination132that includes a ferromagnetic free layer134, an SAF structure136, and a spacer layer138positioned between the free layer and the SAF structure. In some embodiments, the magnetically responsive lamination132can include any suitable layer or layers.

The magnetically responsive lamination132is separated from a sensed data bit140stored in an adjacent medium136by an air bearing surface144. The stack130also includes an AFM structure146that is coupled to the SAF structure136by a predetermined offset distance152from the ABS144. The stack130also includes a first shield layer154proximate the AFM structure146such that the structure is between at least a portion of the first shield layer and the SAF structure136.

In the illustrated embodiment, the magnetically responsive lamination132includes the free layer134that can be sensitive to external magnetic fields. That is, the free layer134can have a magnetization that corresponds to an encountered external magnetic field, such as provided by programmed magnetic bits140on the adjacent storage medium136. The free layer134can include any suitable material or materials, e.g., NiFe, CoFe, CoNiFe, CoFeB, magnetic Heusler alloys, etc.

The SAF structure136of the lamination132is separated from the free layer134by spacer layer138. The SAF structure136can have a predetermined set magnetization. In the embodiment illustrated inFIG. 2, the SAF structure136includes a reference layer160, and a non-magnetic spacer layer158positioned between the reference layer and a pinned layer156, where the pinned layer is proximate the AFM structure146and coupled to the AFM structure and the first shield layer154. In other embodiments, the SAF structure136can include any suitable layer or layers. For example, the SAF structure136can include a lamination of a transition metal, such as Ru, disposed between ferromagnetic crystalline or amorphous sub-layers, such as metals like Ni and Co, alloys like CoFe and NiFe, and high polarization ratio compounds like CoFeB. The reference layer160can include any suitable material or materials, e.g., CoFe, CoFeB, etc.

The spacer layer158can include any suitable material or materials, e.g., Ru, and can have any suitable thickness to accommodate free layer magnetic sensing.

The free layer134and SAF structure136can each be coupled to an electrode layer, e.g., one or more seed layers, cap layers, etc., that provide both manufacturing and operational improvements. For example, the free layer134can be coupled to optional capping layer163. It should be noted, however, that the composition, shape, and placement of the electrode layers are not limited and can be modified or removed.

The pinned layer156is positioned between the spacer layer158and the AFM structure146. In some embodiments, the pinned layer156is coupled to the AFM structure146. Further, in some embodiments, the pinned layer156can be coupled to the first shield layer154. The pinned layer156can include any suitable stripe height168. In some embodiments, the pinned layer156extends to the ABS144. In other embodiments, the pinned layer156is recessed any suitable distance from the ABS144.

Positioned between the free layer134and the SAF structure136is the spacer layer138. The spacer layer138can include any suitable material or materials, e.g., Co, Ag, MgO, TiO, Al2O3, etc. In some embodiments, the spacer layer138can include the same material as the spacer layer158.

In the embodiment illustrated inFIG. 2, the SAF structure136, free layer134, and spacer layer138each extends to the ABS144, e.g., stripe height168. In other embodiments, one or more of these structures and layers may not extend to the ABS144.

Coupled to the SAF structure136is the AFM structure146, which, in the illustrated embodiment, includes an AFM layer164, a first seed layer166, and a second seed layer168positioned between the AFM layer and the first seed layer. In some embodiments, the AFM layer164is coupled to the pinned layer156of the SAF structure136. The AFM layer164can include any suitable material or materials, e.g., IrMn, PtMn, NiMn, IrMnCr, PtMnCr, etc.

While the AFM structure146can, in some embodiments, be attached anywhere along the SAF structure136, the addition of an AFM structure at the ABS would increase the distance between shields154and162(i.e., shield-to-shield spacing), thus limiting the maximum potential areal density readable by the stack130. It has been observed that the AFM structure146can provide acceptable levels of exchange coupling to maintain the set magnetization of the pinned layer156with a length150that is less than the stripe height168. In other words, in some embodiments, the AFM structure146does not extend to the ABS144. And the operational characteristics of the magnetic stack can be adjusted and tuned by varying the size, shape, and position of the AFM structure146on the SAF structure136.

The AFM structure146can take any suitable shape. For example, in the embodiment illustrated inFIG. 2, the AFM structure146includes a surface147that is substantially parallel to the ABS144. In other embodiments, surface147can be anti-parallel to the ABS144. For example, the surface147can be sloped in relation to the ABS144, e.g., AFM structure224ofFIGS. 4A-F.

The addition of the AFM structure146to the magnetic stack130can provide increased performance with robustness against operational variability. That the AFM structure146is complementing the existing set magnetization of the SAF structure136can allow for the reduced length150to complement the SAF structure136without having to impart and maintain the set magnetization in response to the external bits140. As such, the AFM structure146, in some embodiments, is coupled directly to the pinned layer156, as opposed to attaching the AFM structure onto the free layer134, which could impart a bias magnetization onto the free layer.

In some embodiments, the magnetic stack130also includes a first shield layer154proximate the AFM structure146such that the AFM structure is between at least a portion of the first shield layer and the SAF structure136. Specifically, a first region153of the first shield layer154is proximate the AFM structure146such that the structure is between the first region and the SAF structure. In other words, the first shield layer154includes a region of reduced thickness that house a portion of the AFM structure146, e.g., first region153. As can be seen inFIG. 2, a second region155of the first shield layer154is proximate the SAF structure136such that the pinned layer156of the SAF structure is coupled to the first shield layer154.

In some embodiments, the magnetic stack130can include a second magnetic shield layer162proximate the magnetically responsive lamination132. The first and second magnetic shield layers154,162, can include any suitable material or materials, e.g., NiFe, CoNiFe, etc. In some embodiments, the first shield layer154and second shield layer162can include the same materials; in other embodiments, the first shield layer includes material or materials that are different from the material or materials of the second shield layer.

In general, the shield layers154,162can be oriented in a variety of configurations and include a variety of compositions to direct unwanted magnetic flux away from the magnetic lamination of the free layer134and SAF structure136. Such shielding can allow for improved magnetic sensing of programmed bits140from medium136by eliminating noise and inadvertent sensing of adjacent bits.

The stack130can also include an optional capping layer163positioned between the second shield layer162and the free layer134. The capping layer163, which can in some embodiments function as an electrode, can include any suitable material or materials.

Although the magnetic stack130ofFIG. 2includes a single AFM structure146, other embodiments can include two or more AFM structures. Such additional AFM structures can be utilized to pin the magnetization of a shield layer. It has been observed that the rotation of magnetization of a pinned bottom shield, for example, in the opposite direction to that of the free layer (e.g., free layer134ofFIG. 2), with a phase shift, can help to further reduce the magnetic thickness, thereby improving magnetic resolution of the magnetic stack. The reduced physical thickness of the stack can also further increase resolution.

For example,FIG. 3is a schematic cross-section view of a magnetic stack170. The stack170includes a magnetically responsive lamination172. The lamination172includes a ferromagnetic free layer174, an SAF structure176, and a spacer layer178positioned between the ferromagnetic free layer and the SAF structure. The lamination172is separated from a sensed data bit180stored in an adjacent medium182by an ABS184.

The stack170also includes a first AFM structure186coupled to the SAF structure176a predetermined offset distance192from the ABS184. All of the design considerations and possibilities regarding the magnetically responsive lamination132and the AFM structure146of the magnetic stack130ofFIG. 2apply equally to the magnetically responsive lamination172and the first AFM structure186of the magnetic stack170ofFIG. 3.

The stack170also includes a second AFM structure194separated from the first AFM structure186by a first shield layer196. The second AFM structure194can include any suitable AFM structure, e.g., AFM structure146ofFIG. 2. As illustrated inFIG. 3, the second AFM structure194includes an AFM layer214, a first seed layer216, and a second seed layer218positioned between the AFM layer and the first seed layer. All of the design considerations and possibilities regarding the AFM layer164, first seed layer166, and second seed layer168of the AFM structure146ofFIG. 2apply equally to the AFM layer214, the first seed layer216, and the second seed layer218of the second AFM structure194ofFIG. 3. The AFM layer214of the second AFM194is coupled to the first shield layer196.

The second AFM structure194can include the same layers and materials as the first AFM structure186. Alternatively, the second AFM structure194can include different layers and materials from the first AFM structure186.

As illustrated inFIG. 3, the magnetic stack170also includes a second shield layer204proximate the second AFM structure194, and a third shield layer206proximate the magnetically responsive lamination172. The second shield layer204is positioned such that the second AFM structure194is between the first shield layer196and the second shield layer. Any suitable material or materials can be used for the first, second, and third shield layers196,204,206, e.g., materials described for first and second shield layers154,162ofFIG. 2. In some embodiments, the first, second, and third shield layers196,204,206include the same materials; in other embodiments, the first, second, and third shield layers can include different materials.

Similar to magnetic stack130ofFIG. 2, the first shield layer196includes a region of reduced thickness195that houses at least a portion of the first AFM structure186, and another region197that is coupled to pinned layer198.

In the illustrated embodiment, the SAF structure176, free layer174, spacer layer178, and second AFM structure194each extends to the ABS184. In contrast to these layers, the first AFM structure186does not extend to the ABS184. Instead, the first AFM structure186has a stripe height190.

The SAF structure176includes a reference layer202, a pinned layer198, and a non-magnetic spacer layer200positioned between the reference layer and the pinned layer. The pinned layer198is proximate the first AFM structure186and coupled to the first AFM structure and the first shield layer196.

The first AFM structure186includes an AFM layer208, a first seed layer210, and a second seed layer212positioned between the AFM layer and the first seed layer. The AFM layer208of the first AFM structure186is coupled to the SAF structure176.

The stack170also includes an optional capping layer207positioned between the third shield layer206and the free layer174. The capping layer207can include any suitable capping layer, e.g., capping layer163ofFIG. 2.

Any suitable technique can be utilized to form the magnetic stacks of the present disclosure. In some embodiments, such techniques can provide a recessed AFM structure. In some embodiments, such techniques can also separate the heat treatment of the AFM structure and other parts of the magnetic stack to achieve higher pinning, higher blocking temperature of the AFM structure, and higher magnetoresistive response (MR) for the stack.

FIGS. 4A-Fillustrate one exemplary technique for forming a magnetic stack or element (e.g., magnetic stack130ofFIG. 2). As illustrated inFIG. 4A, a shield layer222is formed. Any suitable technique can be utilized to form the shield layer222, e.g., plasma vapor deposition, chemical vapor deposition, plating, etc.

An AFM structure224is formed proximate the shield layer222. In some embodiments, the AFM structure224is formed on the shield layer222. In other embodiments, an additional layer or layers can be formed between the shield layer222and AFM structure224. For example, in some embodiments, an additional AFM structure can be formed (e.g., second AFM structure194ofFIG. 3) followed by forming shield layer222on the additional AFM structure.

In the illustrated embodiment, the AFM structure224includes an AFM layer232, first seed layer234, and second seed layer236. Any suitable AFM structure can be formed on the shield layer222, e.g., AFM structure146ofFIG. 2. Further, any suitable technique can be used to form the layers of the AFM structure224, e.g., physical vapor deposition, heater or room temperature deposition, etc.

A pinned layer226can be formed proximate the AFM structure224. In some embodiments, the pinned layer226can be formed on the AFM structure224. In other embodiments, an additional layer or layers can be formed between the pinned layer226and the SAF structure224. In some embodiments, a capping layer228can also be deposited on the pinned layer226to protect the other layers from chemical-mechanical polishing that can be subsequently performed.

After forming the pinned layer226and optional capping layer228, a photo resist layer229can be formed on the capping layer as shown inFIG. 4B. A portion of the pinned layer226and the AFM structure224can be removed in a region240of the magnetic stack220to expose a portion242of the shield layer222. Any suitable technique or techniques can be used to expose this region of the shield layer, e.g., photolithography, ion milling, reactive ion etching, or combinations thereof. In some embodiments, a high-angle milling technique can be utilized.

Although a surface of the AFM structure224proximate portion242of the shield layer222has a sloped surface, in other embodiments, this surface can be substantially orthogonal to the shield layer.

Additional shield material244is deposited in the region240of the magnetic stack220as shown inFIG. 4C. The additional shield material244backfills at least a portion of the space in the region240where the pinned layer226and the AFM structure224had been removed. The additional shield material244can include any suitable material or materials. In some embodiments, the additional shield material244includes the same material as the material of the shield layer222. In other embodiments, the additional shield material244includes a material different from the material of the shield layer222. Further, in some embodiments, the shield material244is coupled to the shield layer222to in effect form a unitary shield layer222. Any suitable technique can be used to deposit the additional shield material244.

A high-angle milling technique can be used to clear the shield material244from proximate the photoresist229so that a solvent can then be used to remove the photo resist.

The stack220can be planarized to remove the photo resist229and excess shield material244as shown inFIG. 4Dusing any suitable technique, e.g., chemical mechanical polishing, etc. Additional techniques and steps may be performed to augment lift-off of the additional shield material, e.g., a higher angle ion milling (relative to the substrate normal, also known as a knock-off process).

Additional pinned layer material227can be deposited on the shield layer222proximate the pinned layer226such that the pinned layer is extended as shown inFIG. 4E. Any suitable pinned layer material227can be used, e.g., the same material as the material used to form pinned layer226. In other embodiments, the additional pinned layer material227can include material that is different from the material of the pinned layer226. Any suitable technique can be used to form the additional pinned layer material227, e.g., PVD, molecular beam epitaxy (MBE), etc. If a capping layer is present, then the layer is removed prior to depositing additional pinned layer material229.

As shown inFIG. 4F, a spacer layer248, reference layer250, and a magnetically responsive lamination252can be formed proximate the pinned layer226using any suitable technique, e.g., PVD, MBE, etc. Further, the spacer layer248, reference layer250, and magnetically responsive lamination248can include any suitable layer or layers, e.g., the same layers as those described for stack130ofFIG. 2. The pinned layer226, spacer layer248, and reference layer250form an SAF structure254.

Although not shown, other layers can also be formed on stack220, e.g., an additional shield layer on magnetically responsive lamination252, electrode layers, etc., using any suitable techniques.

In other embodiments, a shield layer can first be patterned to provide a recessed AFM structure instead of first forming the AFM structure and then selectively removing portions of both the AFM structure and the shield layer. For example,FIG. 5is a schematic cross-section view of another embodiment of a magnetic stack260. The stack260includes a magnetically responsive lamination262that includes a ferromagnetic free layer264, an SAF structure266, and a spacer layer268positioned between the free layer and the SAF structure. The magnetically responsive lamination262is separated from a sensed data bit270stored in an adjacent medium272by an ABS274. The stack260also includes an AFM structure276that is coupled to the SAF structure266by a predetermined offset distance282from the ABS274. The stack260also includes a first shield layer284proximate the AFM structure276such that the structure is between at least a portion of the first shield layer and the SAF structure266.

The SAF structure266includes a reference layer290, and a non-magnetic spacer layer280positioned between the reference layer and a pinned layer286, where the pinned layer is proximate the AFM structure276and coupled to the AFM structure and the first shield layer276. Further, the AFM structure276includes an AFM layer294, a first seed layer296, and a second seed layer298positioned between the AFM layer and the first seed layer. The SAF structure266and the AFM structure276can include any suitable layer or layers described herein.

Any suitable technique can be utilized to form the stack260ofFIG. 5. For example, in some embodiments, a portion of the first shield layer284is selectively removed using any suitable technique, e.g., ion etching, etc., to form a recess300. Then the AFM structure276is formed in the recess300such that it is offset a predetermined distance282from the ABS274.

All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure. Illustrative embodiments of this disclosure are discussed and reference has been made to possible variations within the scope of this disclosure. These and other variations and modifications in the disclosure will be apparent to those skilled in the art without departing from the scope of the disclosure, and it should be understood that this disclosure is not limited to the illustrative embodiments set forth herein. Accordingly, the disclosure is to be limited only by the claims provided below.