Heat assisted magnetic recording head with multilayer electromagnetic radiation emission structure

A heat assisted magnetic recording head with a multilayer electromagnetic (EM) radiation emission structure. The multilayer EM radiation emission structure is in optical communication with a light source for heating a recording medium. Particularly, the multilayer EM radiation emission structure includes a conducting layer for receiving the light source and a protective layer formed adjacent the conducting layer to protect the conducting layer from contact with a recording medium. An aperture extends through the conducting layer in the protective layer to allow the light source to pass therethrough to heat the recording medium.

FIELD OF THE INVENTION

The invention relates to heat assisted magnetic recording heads, and more particularly, to a multilayer electromagnetic radiation emission structure for heat assisted magnetic recording.

BACKGROUND INFORMATION

Magnetic recording heads have utility in a magnetic disc drive storage system. There is a demand in the disc drive storage industry to develop magnetic recording heads having an increased areal storage density. However, one obstacle in achieving increased areal storage density is the “superparamagnetic limit”, which is also sometimes referred to as the “superparamagnetic effect” This well known phenomenon generally refers to the point at which the thermal activity of an object, such as the individual grains that make up a recording layer of a magnetic recording medium, is so great that the magnetization is no longer stable, i.e. the object becomes thermally unstable and incapable of maintaining it's desired magnetization.

A development that overcomes at least some of the problems associated with the superparamagnetic limit is heat assisted magnetic recording, sometimes referred to as optical assisted or thermal assisted recording (all of which will be collectively referred to herein as “heat assisted magnetic recording”). Heat assisted magnetic recording generally refers to the concept of locally heating a recording medium to reduce the coercivity of the recording medium so that the applied magnetic writing field can more easily direct the magnetization of the recording medium during the temporary magnetic softening of the recording medium caused by the heat source. The heat assisted magnetic recording allows for the use of small grain media, which is desirable for recording at increased areal densities, with a larger magnetic anisotropy at room temperature and assuring a sufficient thermal stability.

More specifically, superparamagnetic instabilities become an issue as the grain volume is reduced in order to control media noise for high areal density recording. The superparamagnetic limit is most evident when the grain volume V is sufficiently small that the inequality KuV/kBT>40 can no longer be maintained. Kuis the material's magnetic crystalline anisotropy energy density, kBis Boltzmann's constant, and T is absolute temperature. When this inequality is not satisfied, thermal energy demagnetizes the individual grains and the stored data bits will not be stable. Therefore, as the grain size is decreased in order to increase the areal density, a threshold is reached for a given material Kuand temperature T such that stable data storage is no longer feasible.

The thermal stability can be improved by employing a recording medium formed of a material with a very high Ku. However, with the available materials the recording heads are not able to provide a sufficient or high enough magnetic writing field to write on such a medium. Accordingly, it has been proposed to overcome the recording head field limitations by employing thermal energy to heat a local area on the recording medium before or at about the time of applying the magnetic write field to the medium. By heating the medium, the Kuor the coercivity is reduced such that the magnetic write field is sufficient to write to the medium. Once the medium cools to ambient temperature, the medium has a sufficiently high value of coercivity and assures thermal stability of the recorded information.

Various structures or devices have been proposed for heating a recording medium for heat assisted magnetic recording, such as, for example, a waveguide, a solid immersion lens or a surface plasmon lens. When applying a heat source to the recording medium, it is desirable to confine the heat to the track where writing is taking place. Thus, it is necessary to produce a very small, intense hot spot to heat the recording medium only in the desired location. To achieve the small, intense hot spot it has been proposed to use a near-field optical probe, such as an optical antenna, to focus optical energy through a very small aperture to produce the necessary thermal energy for heating the recording medium. Accordingly, various optical antenna designs having such a small aperture for creating the small, intense heat spot on the recording medium are known. For example,FIG. 1aillustrates a bow tie antenna10aandFIG. 1billustrates a circular antenna10b, each having a small aperture area12aand12brespectively.

Such optical antennas are typically made from a suitable conducting material such as Au or Ag to support plasmons from a light beam that will propagate through the apertures12aor12bto generate the hot spot. However, such materials are generally mechanically soft and are not well suited to withstand the start/stop and intermittent contact with the recording medium that is typically existent in low flying disc recording systems.

Although it is generally known to provide an overcoat material, such as a diamond-like carbon overcoat (DLC) on the air-bearing surface (ABS) of a slider or a recording head, such an overcoat alone is not effective in protecting the proposed structures for heat assisted magnetic recording. For example, the DLC does not adhere well to the optical antenna designs formed of a material such as Au or Ag. In addition, the DLC depositions are usually done in chambers specifically designed for only DLC processing, which increases manufacturing costs.

Accordingly, there is identified a need for an improved heat assisted magnetic recording head that overcomes limitations, disadvantages, and/or shortcomings of known heat assisted magnetic recording heads.

SUMMARY OF THE INVENTION

Embodiments of the invention meet the identified needs, as well as other needs, as will be more fully understood following a review of the specification and drawings.

In accordance with an aspect of the invention, a heat assisted magnetic recording head for use in conjunction with a recording medium comprises means for applying a magnetic write field to the recording medium, means for providing a light source, and a multilayer electromagnetic (EM) radiation emission structure in optical communication with the means for providing a light source. The multilayer EM radiation emission structure defines an aperture that extends therethrough. The multilayer EM radiation emission structure may include a conducting layer in optical communication with the means for providing a light source and a protective layer formed between the conducting layer and the recording medium to protect the conducting layer from contact with the recording medium. The multilayer EM radiation emission structure may be, for example, an optical antenna.

In accordance with an additional aspect of the invention, a multilayer EM radiation emission structure in optical communication with a light source for heating a recording medium comprises a conducting layer for receiving the light source and a protective layer formed adjacent the conducting layer. The conducting layer defines a first aperture that extends therethrough. The protective layer defines a second aperture that extends therethrough and that is in alignment with the first aperture to allow the light source to pass therethrough to heat the recording medium. The multilayer EM radiation emission structure may also include an additional conducting layer formed on at least a portion of a sidewall of the first aperture and the second aperture. In addition, the multilayer heat emission structure may also include an additional protective layer formed on at least a portion of the additional conducting layer.

In accordance with another aspect of the invention, a method of making a multilayer EM radiation emission structure for use with a light source to heat a recording medium comprises depositing a conducting layer for optically communicating with the light source, depositing a protective layer adjacent the conducting layer for protecting the conducting layer from contact with the recording medium, and forming an aperture that extends through the conducting layer and the protective layer to allow the light source to pass therethrough to heat the recording medium.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a heat assisted magnetic recording head, and more particularly a multilayer electromagnetic (EM) radiation emission structure for heat assisted magnetic recording. The invention is particularly suitable for use with a magnetic disc drive storage system although it will be appreciated that the invention may also be used with other type storage systems, such as, for example, magneto-optical or optical storage systems. A recording head, as used herein, is generally defined as a head capable of performing read and/or write operations. Perpendicular magnetic recording, as used herein, generally refers to orienting magnetic domains within a magnetic storage medium substantially perpendicular to the direction of travel of the recording head and/or recording medium.

FIG. 2is a pictorial representation of a disc drive10that can utilize a heat assisted magnetic recording head, which may be a perpendicular magnetic recording head, constructed in accordance with this invention. The disc drive10includes a housing12(with the upper portion removed and the lower portion visible in this view) sized and configured to contain the various components of the disc drive. The disc drive10includes a spindle motor14for rotating at least one magnetic storage medium16, which may be a perpendicular magnetic recording medium, within the housing. At least one arm18is contained within the housing12, with each arm18having a first end20with a recording head or slider22, and a second end24pivotally mounted on a shaft by a bearing26. An actuator motor28is located at the arm's second end24for pivoting the arm18to position the recording head22over a desired sector or track27of the disc16. The actuator motor28is regulated by a controller, which is not shown in this view and is well known in the art.

FIG. 3is a partially schematic side view of a heat assisted magnetic recording head22and a magnetic recording medium16. Although an embodiment of the invention is described herein with reference to recording head22as a perpendicular magnetic recording head and the medium16as a perpendicular magnetic recording medium, it will be appreciated that aspects of the invention may also be used in conjunction with other type recording heads and/or recording mediums where it may be desirable to employ heat assisted recording. Specifically, the recording head22may include a writer section comprising a main write pole30and a return or opposing pole32that are magnetically coupled by a yoke or pedestal35. It will be appreciated that the recording head22may be constructed with a write pole30only and no return pole32or yoke35. A magnetization coil33surrounds the yoke or pedestal35for energizing the recording head22. The recording head22also may include a read head, not shown, which may be any conventional type read head as is generally known in the art.

Still referring toFIG. 3, the recording medium16is positioned adjacent to or under the recording head22. The recording medium16includes a substrate38, which may be made of any suitable material such as ceramic glass or amorphous glass. A soft magnetic underlayer40is deposited on the substrate38. The soft magnetic underlayer40may be made of any suitable material such as, for example, alloys or multilayers having Co, Fe, Ni, Pd, Pt or Ru. A hard magnetic recording layer42is deposited on the soft underlayer40, with the perpendicular oriented magnetic domains44contained in the hard layer42. Suitable hard magnetic materials for the hard magnetic recording layer42may include at least one material selected from, for example, FePt or CoCrPt alloys having a relatively high anisotropy at ambient temperature.

The recording head22also includes means for providing a light source and a multilayer EM radiation emission structure46to heat the magnetic recording medium16proximate to where the write pole30applies the magnetic write field H to the recording medium16. Specifically, the means for providing a light source may include, for example, an optical waveguide schematically represented by reference number50. The optical waveguide50acts in association with a light source52which transmits light via an optical fiber54that is in optical communication with the optical waveguide50. The light source52may be, for example, a laser diode, or other suitable laser light sources. This provides for the generation of a guided mode that may propagate through the optical waveguide50toward the multilayer EM radiation emission structure46(as indicated by arrows48) that is formed along the air-bearing surface (ABS) of the recording head22. EM radiation, generally designated by reference number58, is transmitted from the EM radiation emission structure46for heating the recording medium16, and particularly for heating a localized area “A” of the recording layer42.

The optical waveguide50may include a light transmissive material in optical communication with the light source52and optical fiber54, as is generally known. The light transmissive material provides for the described generation of a guided mode which propagates toward the EM radiation emission structure46. The light transmissive material may be formed, for example, from a material, such as SiO2, SiN or TiO2, as is generally known.

In addition to the optical waveguide50, the means for providing a light source may include other structures or devices such as, for example, a solid immersion lens.

Referring toFIGS. 3 and 4, the multilayer EM radiation emission structure46is illustrated, for example, in the form of a generally circular optical antenna. However, it will be appreciated that the multilayer EM radiation emission structure of the present invention may be constructed in various shapes and configurations, such as, for example, a bow tie optical antenna or a C-shaped optical antenna structure. Specifically, the EM radiation emission structure46includes a conducting layer60and a protective layer62. The conducting layer60is positioned for optical communication with the light energy48that propagates from the optical waveguide50, as described herein. The protective layer62is formed adjacent the conducting layer60and positioned between the conducting layer60and the recording medium16so as to protect the conducting layer60from contact with the recording medium16.

The conducting layer60may comprise at least one material selected from the group consisting of Au, Ag, or Al. The conducting layer60may have a thickness60tin the range of about 10 nm to about 1000 nm.

The protective layer62may comprise at least one material selected from the group consisting of Ta, Ti, W, Mo or Cr. The protective layer62may have a thickness62tin the range of about 0.5 nm to about 100 nm.

As best shown inFIG. 4, the EM radiation emission structure46defines an aperture64that extends therethrough, and particularly extends through the conducting layer60and the protective layer62. The propagating light48impinges upon the conducting layer60of the EM radiation emission structure46. The aperture64may serve as a filter to filter out all of the light outside of the aperture width W1, or surface plasmons may be generated by the light48impinging upon the conducting layer60. If plasmons are generated, they may propagate along the surface of the layer60to the aperture64and enhance the amount of light passing therethrough.

As it is important to develop a small, intense hot spot to heat the area “A” of the recording medium16, the aperture64has a width W1in the range of about 1 nm to about 250 nm.

The formation of the EM radiation emission structure46having the protective layer62between the conducting layer60and the recording medium16is beneficial because, as stated, the conducting layer60is formed of a mechanically soft conducting material that is not well suited to withstand any possible start/stop and intermittent contact that may occur with the recording medium, as is typically existent in low flying magnetic disc recording systems. The protective layer62better serves to protect the conducting layer60than other known techniques that are employed for protecting recording heads, and particularly the ABS thereof, from contact with the recording medium16. Such known techniques include, for example, providing an overcoat material, such as a diamond-like carbon overcoat (DLC) on the ABS of a slider or a recording head22.

An advantage of having the protective layer62as opposed to merely relying on the DLC overcoat is that the mechanically hard protective layer62adheres better to the conducting layer60as compared to the adhesion of the DLC overcoat to the conducting layer60.

Another advantage is that the material for forming the protective layer62may be chosen such that the DLC overcoat adheres well thereto and the DLC overcoat more easily forms a thin uniform coating. It will be appreciated that the EM radiation emission structure46may also include, if desired, a DLC overcoat applied to the ABS thereof, i.e., a DLC overcoat applied to the ABS of the protective layer62. Specifically, the thin film growth mode is mainly governed by surface and interface free energies. For example, if the conducting layer60is formed of Au (which has a relatively low surface free energy) and if it does not form a suitably strong bond with the C of the DLC overcoat, a thin continuous layer of DLC will not be possible. On the other hand, if the protective layer62is formed of Ta which may form bonds with Au, it may effectively coat the Au and then a thin DLC coating could be applied to the Ta protective layer62.

Another advantage of employing the protective layer62as opposed to using the DLC overcoat, is that the protective layer62actually defines a portion of the aperture64. This means that the protective layer62can be made much thicker than the layer of DLC overcoat and, therefore, more reliable than the DLC overcoat.

Yet another advantage of the protective layer62is that it can reduce the edge coupling of the plasmons to the medium16and since the plasmons would not propagate along the hard protective layer62, the thermal profile would be much sharper with reduced side heating.

Referring toFIG. 5, there is illustrated an additional embodiment of the invention which includes a multilayer EM radiation emission structure146that is similar to the multilayer EM radiation emission structure46described herein. Specifically, the EM radiation emission structure146may include a conducting layer160and a protective layer162. The conducting layer160and the protective layer162define an aperture164that extends therethrough. The EM radiation emission structure146may include an additional conducting layer166that may be formed on at least a portion of a sidewall168of the aperture164and/or on at least a portion of the ABS of the EM radiation emission structure146. The additional conducting layer166may comprise at least one material selected from the group consisting of Au, Ag, or Al. An advantage of having an additional conducting layer166, and particularly of having an additional conducting layer166formed on at least a portion of the sidewall168of the aperture164, is that the width of the aperture164may be reduced to a width of W2to allow for the generation of an even smaller, intense hot spot “A” on the recording medium16. W2may be in the range of about 1 nm to about 50 nm.

Still referring toFIG. 5, the EM radiation emission structure146may also include an additional protective layer172that may be formed on at least a portion of the additional conducting layer166. The protective layer162may or may not be used in conjunction with the additional protective layer172. The additional protective layer172may comprise at least one material selected from the group consisting of Ta, Ti, W, Mo or Cr. An advantage of providing the additional protective layer172is that the width of the aperture164may be further reduced to the width W3to produce an even smaller, intense hot spot for heating the recording medium16. W3may be in the range of about 1 nm to about 50 nm. In addition, it will be appreciated that the additional protective layer may be formed directly on at least a portion of the sidewall168of the aperture164or on the ABS of the heat emission structure146.

In the situation where surface plasmons are being generated, the layer162would need to be made of a material, such as Au, Ag, or Al, that would support propagation of these plasmons. The protective layer172may or may not be used to further reduce the width of the aperture164. However, the protective layer172would need to be constructed of a material, such as Ta, Ti, W, Mo, or Cr, that would stop the propagation of the plasmons and allow for the energy to be transmitted to the recording medium16to heat the localized area A thereof.

If surface plasmons are not being utilized, the layer162could be formed of any non-transparent material, such as Ta, Ti, W, Mo, Cr, Zr, Nb, Al, or Ag. The protective layer172would then be needed to protect the layer162in the event that it was formed of a relatively soft material.

The means for providing a light source and the EM radiation emission structures46and146may be located adjacent to the write pole30. Advantageously, this would allow for heating of the recording medium16in close proximity to where the write pole30applies the magnetic write field H to the recording medium16. It also provides for the ability to align the EM radiation emission structures46and146with the write pole30to maintain the heating application in the same track27of the medium16where the writing is taking place. Locating the EM radiation emission structures46and146adjacent to the write pole30provides for increased writing efficiency due to the write field H being applied immediately downtrack from where the recording medium16has been heated. It will be appreciated that the structures46and/or146may be positioned in different locations relative to the write pole30for heating the medium16either before, after or at about the same time as the write field H is applied.

In operation, the recording medium16is passed under the recording head22. The recording medium16may travel in either direction under the recording head22since the write pole30and the EM radiation emission structure46are located in close proximity. The light source52transmits light energy via the optical fiber54to the optical waveguide50. The optical waveguide50transmits the light energy to the EM radiation emission structure46or146for heating the recording medium16. More specifically, a localized area A of the recording layer42is heated to lower the coercivity thereof prior to the write pole30applying a magnetic write field H to the recording medium16. Advantageously, this allows for a higher coercivity medium material to be used which limits the superparamagnetic instabilities that may occur with such recording media used for high recording densities.

At a downtrack location from where the medium16is heated, the magnetic write pole30applies a magnetic write field to the medium16for storing magnetic data in the recording medium16. The write field H is applied while the recording medium16remains at a sufficiently high temperature for lowering the coercivity of the recording medium16. This insures that the write pole30can provide a sufficient or strong enough magnetic write field to perform a write operation on the recording medium16.

The invention also includes a method for making the multilayer EM radiation emission structures46and146. Specifically, the method includes depositing the conducting layer60for optically communicating with the means for providing a light source as described herein. The method also includes depositing the protective layer62adjacent the conducting layer60such that the protective layer62is positioned for protecting the conducting layer60from contact that may occur with the recording medium16. The protective layer62may be deposited so as to be in direct contact with the conducting layer60or an interlayer could be used therebetween to promote adhesion between the conducting layer60and the protective layer62. The depositing of the conducting layer60and the protective layer62may be carried out using conventional deposition techniques such as, for example, sputtering or ion beam deposition.

The method also includes forming the aperture64that extends through the conducting layer60and the protective layer62to allow the light energy to pass therethrough to heat the recording medium16. Formation of the aperture64may include some additional post-deposition processing. For example, known techniques of an etching process or a lift-off process could be utilized in forming the aperture64.

The method of making the EM radiation emission structure146, illustrated inFIG. 5, may include additional steps to deposit the additional conducting layer166and/or the additional protective layer172. The deposition of the additional conducting layer166and/or the additional protective layer172may be carried out using a directional deposition technique such as, for example, ion beam deposition, evaporation, or collimated sputtering which would provide for sufficient film growth rate on the sidewall168of the aperture164. The directional deposition of the additional conducting layer166and/or the additional protective layer172is applied, as indicated by arrows D at an angle with respect to the plane of the conducting layer160and the protective layer162. The angle of the deposition D and the angle at which the incoming material would make contact with the surface can be used to control how deep the conductive layer166and/or the protective layer172extends into the aperture164. This further enhances the ability to form the additional conducting layer166and/or the additional protective layer172on the sidewall168.

Whereas particular embodiments have been described herein for the purpose of illustrating the invention and not for the purpose of limiting the same, it will be appreciated by those of ordinary skill in the art that numerous variations of the details, materials, and arrangement of parts may be made within the principle and scope of the invention without departing from the invention as described in the appended claims.