Magnetoresistive structure having a novel specular and barrier layer combination

A method and system for providing a magnetoresistive structure is disclosed. The magnetoresistive structure includes a pinned layer, a nonmagnetic spacer layer, a free layer, a specular layer, a barrier layer, and a capping layer. The spacer layer resides between the pinned layer and the free layer. The free layer is electrically conductive and resides between the specular layer and the nonmagnetic spacer layer. The specular layer is adjacent to the free layer and includes at least one of titanium oxide, yttrium oxide, hafnium oxide, magnesium oxide, aluminum oxide, nickel oxide, iron oxide, zirconium oxide, niobium oxide, and tantalum oxide. The barrier layer resides between the specular layer and the capping layer. The barrier layer is nonmagnetic and includes a first material. The capping layer includes a second material different from the first material.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to co-pending U.S. application Ser. No. 11/114,295, entitled “Magnetoresistive Structure Having a Novel Specular Layer” filed on Apr. 26, 2005 and assigned to the assignee of the present application. The present application is related to co-pending U.S. application Ser. No. 11/114,255 entitled “Magnetoresistive Structure Having a Novel Specular and Filter Layer Combination” filed on Apr. 26, 2005 and assigned to the assignee of the present application.

FIELD OF THE INVENTION

The present invention relates to magnetic recording technology, and more particularly to a method and system for providing an improved magnetic structure, such as a spin valve or spin filter.

BACKGROUND OF THE INVENTION

In the effort toward achieving higher data density on recording media, spin filters have become of interest for use in magnetoresistive (MR) read heads.FIG. 1is a diagram of a conventional spin filter10. In general, the conventional spin filter10would be incorporated into a MR read head (not explicitly shown), which would include leads electrically connected to other electronics to drive current through the conventional spin filter10during reading. In such an application, current is generally driven in the current perpendicular to the plane (CPP) configuration. The CPP configuration is in the z-direction depicted inFIG. 1.

The conventional spin filter10includes a seed layer12, an antiferromagnetic (AFM) layer14, a pinned layer16, a nonmagnetic spacer layer24, a free layer26, a filter layer28, a specular oxide layer30, and a capping layer32. The seed layer12is used to provide the appropriate surface for growing the AFM layer14with the desired crystal structure. The AFM layer14is used in pinning the magnetization of the pinned layer16. The pinned layer16may be a synthetic pinned layer, including ferromagnetic layers18and22separated by an electrically conductive spacer layer20that is typically Ru. The electrically conductive spacer layer20has a thickness configured to ensure that the ferromagnetic layers18and22are antiferromagnetically coupled. Thus, the magnetization of the ferromagnetic layer18is pinned by the AFM layer14. The magnetization of the ferromagnetic layer22is set because it is strongly antiferromagnetically coupled to the magnetization of the ferromagnetic layer18. The nonmagnetic spacer layer24is typically electrically conductive, for example Cu. The free layer26is ferromagnetic and typically includes materials such as CoFe.

The filter layer28has a high electrical conductivity and typically includes materials such as Cu. The specular oxide layer30may be a nano-oxide and typically includes materials such as alumina. The combination of the filter layer28and the specular oxide layer30has been used to provide adequate specularity of scattering of electrons from the free layer26that are incident on the specular oxide layer30. In particular, the filter layer28has been utilized in the conventional spin filter10to provide a region, or filter, for specular reflection between the free layer26and specular layer30. Thus, the magnetoresistance of the conventional spin filter10is improved. Consequently, the magnetoresistance of the conventional spin filter10is adequate. The capping layer32is typically oxidized Ta.

Although the conventional spin filter10functions, there are drawbacks to the use of the conventional spin filter10. Insertion of the specular oxide layer30can increase the coercivity of the free layer26, which is undesirable. Furthermore, the specular oxide layer30is generally a nano-oxide that can continue to oxidize during processing. The signal may degrade during the lifetime of the conventional spin filter10. The conventional spin filter10thus suffers thermal instabilities and may have reduced reliability.

Accordingly, what is needed is a system and method for providing a spin filter having improved thermal stability, signal sensitivity, and/or reliability.

SUMMARY

The present invention provides a method and system for providing a magnetic structure. The magnetoresistive structure comprises a pinned layer, a nonmagnetic spacer layer, a free layer, a specular layer, a barrier layer, and a capping layer. The spacer layer resides between the pinned layer and the free layer. The free layer is electrically conductive and resides between the specular layer and the nonmagnetic spacer layer. The specular layer is adjacent to the free layer and includes at least one of titanium oxide, yttrium oxide, hafnium oxide, magnesium oxide, aluminum oxide, nickel oxide, iron oxide, zirconium oxide, niobium oxide, and tantalum oxide. The barrier layer resides between the specular layer and the capping layer. The barrier layer is nonmagnetic and includes a first material. The capping layer includes a second material different from the first material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present application is related to co-pending U.S. application Ser. No. 11/114,295 entitled “Magnetoresistive Structure Having a Novel Specular Layer” (Co-pending application 1) filed on Apr. 26, 2005 and assigned to the assignee of the present application. The present application is related to co-pending U.S. Application Ser. No. 11/114,255 entitled “Magnetoresistive Structure Having a Novel Specular and Filter Layer Combination” (Co-pending application 2) filed on Apr. 26, 2005 and assigned to the assignee of the present application. Applicant hereby incorporates by reference the above-identified co-pending applications 1 and 2.

FIGS. 2A and 2Bdepict embodiments of spin filters50and50′ formed using the teachings of the above-identified co-pending patent applications. The spin filter50includes a seed layer52, a pinning layer54that is typically an AFM layer, a pinned layer56, a spacer layer64, a free layer66, a filter layer68, a specular oxide layer70, and a capping layer72. The pinned layer56may be a synthetic pinned layer including ferromagnetic layers58and62separated by a conductive, nonmagnetic spacer layer60. The spacer layer64is nonmagnetic and may be conductive. The free layer66is electrically conductive and resides between the filter layer68and the nonmagnetic spacer layer64. The specular layer70includes at least one of titanium oxide, alumina, zirconium oxide, and niobium oxide. The filter layer68includes at least one of gold and silver if the specular layer70includes alumina. The spin filter50′ includes layers52′,54′,56′,58′,60′,62′,64′,66′,68′,70′, and72′. However, the spin filter50′ also includes a barrier layer80. In addition, the specular layer70′ may include a first material and is electrically insulating. The barrier layer80resides between the specular layer70′ and the capping layer72′. The barrier layer80is nonmagnetic and includes a second material different material from the first material. The capping layer72′ includes a third material different from the second material.

The spin filters50and50′ may have the desired signal without the adversely affecting the electrical resistance. Consequently, the performance of the spin filters50and50′ may be improved. Moreover, it is noted that the spin filter50/50′ may be used in either a CPP or CIP (current in plane) configuration. Although the spin filters50and50′ function, they may suffer from damage during processing. Consequently, a magnetic structure having improved performance and reliability is desired.

FIG. 3depicts a magnetic structure100formed in accordance with an exemplary embodiment of the present invention. For clarity, the magnetic structure100is not depicted to scale. The magnetic structure100includes a pinning layer120, pinned layer130, nonmagnetic spacer layer140, a free layer150, a specular layer160, a barrier layer170and a capping layer180. The magnetic structure100may also include seed layer(s)110used to ensure that the pinning layer120has the desired crystal structure and, therefore, magnetic properties. For example, the seed layer(s)110might include Ta, Ta/NiFe, NiCr, NiFeCr, Ru, NiFe, CoFe or any combination thereof.

The pinning layer120is generally an AFM layer. The AFM materials used in the pinning layer120is preferably IrMn, but can include other AFM materials. For example, the AFM materials used may include, but are not limited to PtMn, NiMn, PtCrMn, and IrMn. The pinned layer130is depicted as a simple layer, but is preferably a synthetic pinned layer, as described in connection withFIG. 4, below. In the embodiment shown, the magnetization of the ferromagnetic layer130is pinned by the pinning layer120.

The nonmagnetic spacer layer140is preferably an electrical conductor, such as Cu. The nonmagnetic spacer layer140thus may include Cu, Ta, Pt, Au, or Ag, alloy(s) thereof, and/or other low electrical resistance material(s). In another embodiment, the nonmagnetic spacer layer140may be an insulator. In such an embodiment, the nonmagnetic spacer layer140is preferably sufficiently thin to act as a tunneling barrier. The free layer150as well as the pinned layer130may include materials such as Co1-xFexalloy, where x can vary from one to ninety-nine atomic percent and/or NiFe. However, other suitable materials may be used. In addition, although a simple free layer is depicted, a synthetic free layer may be used for the free layer150.

The magnetic structure100also includes the specular layer160, barrier layer170, and capping layer180in accordance with the present invention. The specular layer160is configured such that current carriers from the free layer150tend to undergo specular reflection by the specular oxide layer. The specular layer160is preferably a nano-oxide layer and is, therefore, insulating. The specular layer160may thus be formed by a plasma oxidation of the metallic materials. However, other processes such as natural and radical oxidation may be used. The specular layer160includes at least one of titanium oxide, yttrium oxide, hafnium oxide, magnesium oxide, aluminum oxide, nickel oxide, iron oxide, zirconium oxide, niobium oxide, and tantalum oxide. In a preferred embodiment, the specular layer consists essentially of titanium oxide. The specular layer160has a thickness of between five and thirty Angstroms, and more preferably a thickness of between eight and fifteen Angstroms.

The barrier layer170is configured to reduce or prevent intermixing between the capping layer180and the specular layer160. In addition, if the barrier layer170includes a first material, then the capping layer180includes a second material different from the first material. In one embodiment, the barrier layer170includes at least one of Cu, Pt, Au, and Ag. In a preferred embodiment, the barrier layer170consists essentially of Cu. The barrier layer170may have a thickness of at least five and not more than forty Angstroms. In a preferred embodiment, the thickness of the barrier layer is at least twenty-five and not more than thirty-five Angstroms.

The capping layer180is a capping layer formed of a different material than the barrier layer170. In one embodiment, the capping layer180includes material(s) such as a Ta layer or a Ti layer that have been formed into a natural oxide.

The properties of the specular layer160, the barrier layer170, and the free layer150are related. In particular, the magnetic structure100is analogous to a spin filter. Thus, the magnetic structure100exhibits giant magnetoresistance. However, as can be seen inFIG. 3, a filter layer has been omitted. Specular reflection in and around the specular layer160may be moved closer to the free layer170and incomplete specular scattering may be reduced by the omission of a filter layer. Thus, the magnetic structure100may have improved giant magnetoresistance. In addition, the barrier layer170is configured to prevent the specular layer160from intermixing with other layers, such as the capping layer180. Moreover, the barrier layer has a preferred thickness, between twenty-five and thirty-five Angstroms. In particular, the interface between the barrier layer170and the specular layer160for a barrier layer170in the preferred thickness range may improve the magnetic properties, such as giant magnetoresistance, of the magnetic structure100. Furthermore, the preferred thickness of the barrier layer170, the reliability of the magnetic structure100may also be improved. In addition, damage during processing for the magnetic structure100having the combination of the free layer150, specular layer160, and barrier layer170described above may also be reduced.

Thus, the magnetic structure100may have the desired signal. In some embodiments, the magnetic structure may have a giant magnetoresistance higher than that of the conventional spin filter10, the spin filters50and50′, and conventional spin valves (not shown). This may be achieved without the adversely affecting the reliability. Consequently, both the performance and the reliability of the magnetic structure100may be improved. Moreover, it is noted that the magnetic structure100may be used in either a CPP or CIP (current in plane) configuration.

FIG. 4depicts a magnetic structure100′ formed in accordance with another exemplary embodiment of the present invention. For clarity, the magnetic structure100′ is not depicted to scale. The magnetic structure100′ is analogous to the magnetic structure100. The magnetic structure100′ includes a pinning layer120′, pinned layer130′, nonmagnetic spacer layer140′, a free layer150′, a specular layer160′, a barrier layer170′, a capping layer180′, and may include seed layer(s)110′ that are analogous to the layers120,130,140,150,160,170, and180, respectively. For example, the specular layer160′ is configured such that current carriers from the free layer150′ tend to undergo specular reflection by the specular oxide layer160′. Thus, the specular layer160′ includes at least one of titanium oxide, yttrium oxide, hafnium oxide, magnesium oxide, aluminum oxide, nickel oxide, iron oxide, zirconium oxide, niobium oxide, and tantalum oxide. The specular layer160′ preferably includes titanium oxide. Similarly, the barrier layer180′ is configured to prevent the specular layer170′ from intermixing with the capping layer170′ and includes material(s) that are not the same as the capping layer180′. The barrier layer170′ thus preferably includes Cu, and may also include Pt, Au, and/or Ag. In addition, the thickness ranges of the specular layer160′ and the barrier layer170′ are preferably the same as for the specular layer160and the barrier layer170, respectively.

However, the pinned layer130′ is a synthetic pinned layer including ferromagnetic layers132and136separated by a spacer layer134. The spacer layer134is preferably Ru. The thickness of the spacer layer is selected such that the ferromagnetic layers132and136are antiferromagnetically coupled.

The magnetic structure100′ shares the benefits of the magnetic structure100. Thus, the magnetic structure100′ may have improved magnetoresistance. This may be achieved without the adversely affecting the reliability. Consequently, both the performance and the reliability of the magnetic structure100′ may be improved. In addition, the magnetic structure100′ may be used in either a CPP or CIP configuration.

FIG. 5is a diagram of a magnetic structure100″ formed in accordance with another exemplary embodiment of the present invention. For clarity, the magnetic structure100″ is not depicted to scale. The magnetic structure100′ includes components analogous to the components of the magnetic structure100′. Consequently, the magnetic structure100″ includes a pinning layer120″, pinned layer130″, nonmagnetic spacer layer140″, a free layer150″, a specular layer160″, a barrier layer170″, and a capping layer180″. The magnetic structure100may also include seed layer(s)110″.

The layers110″,120″,130″,132′,134′,140″,150″,160″,170″, and180″ preferably have the same structure and function as the layers110′,120′,130′,132,134,140′,150′,160′,170′, and180′, respectively. For example, the specular layer160″ includes at least one of titanium oxide, yttrium oxide, hafnium oxide, magnesium oxide, aluminum oxide, nickel oxide, iron oxide, zirconium oxide, niobium oxide, and tantalum oxide. The specular layer160″ preferably includes titanium oxide. Thus, the specular layer160″ is configured such that current carriers from the free layer150″ tend to undergo specular reflection by the specular oxide layer. Similarly, the barrier layer170″ is configured to prevent the specular layer160″ from intermixing with the capping layer180″. The barrier layer170″ includes material(s) that are not the same as the capping layer180″. The barrier layer170″ thus preferably includes Cu, and may also include Pt, Au, and/or Ag. In addition, the thickness ranges of the specular layer160″ and the barrier layer170″ are preferably the same as for the specular layer160and the barrier layer170, respectively.

The magnetic structure100″ also includes an additional specular oxide layer190, which resides within the ferromagnetic layer136″. The specular oxide layer190is preferably a nano-oxide layer. Thus, the ferromagnetic layer136″ includes ferromagnetic layers136A and136B. The specular oxide layer190is configured such that current carriers from the free layer150″ tend to undergo specular reflection by the specular oxide layer190.

The magnetic structure100″ shares many of the benefits of the magnetic structures100and100′. Thus, the magnetic structure100′ may have improved thermal stability and performance. Moreover, the magnetic structure100″ may be used in either a CPP or CIP configuration.

FIG. 6is a high-level flow chart depicting a method200for fabricating a magnetic structure in accordance with an exemplary embodiment of the present invention. The method200is described in the context of the magnetic structure100′. However, the method200may be used for another magnetic structure consistent with the present invention. Moreover, the method200is described in the context of forming a single magnetic structure100′. One of ordinary skill in the art will readily recognize, however, that the method200may be used in simultaneously forming multiple magnetic structures and/or other magnetic structure(s) consistent with the present invention.

The method200preferably commences after the pinning layer120′ has been provided. The pinned layer130′ is provided, via step202. Step202preferably includes providing the ferromagnetic layers132and136, as well as the spacer layer134. The nonmagnetic spacer layer140′ is provided, via step204. Step204preferably includes providing an electrically conductive layer, such as Cu. However, in an alternate embodiment, an insulator forming a tunneling barrier is provided in step204. The free layer150′ is provided such that the nonmagnetic spacer layer140′ resides between the free layer150′ and the pinned layer130′, via step206. The specular layer160′ is provided on the free layer150′, via step208. In a preferred embodiment, the specular layer160is provided in step208by depositing a metallic layer, then oxidizing the metal layer. In a preferred embodiment, a plasma oxidation process preferably from ten to three hundred seconds is used to oxidize the specular metals. However, other oxidation processes such as natural oxidation or radical oxidation may have similar utility. The barrier layer170′ is provided, via step210. The barrier layer170′ provided in step210includes a first material, such as Cu, Pt, Au, or Ag. The capping layer180is provided, via step212. The capping layer190includes a second material different from the first material.

Using the method200, the magnetic structure100,100′, and/or100″ may be provided.