Patent Application
20190027173
Provided herein is heat assisted magnetic recording (HAMR) media to store information. The apparatus includes a first write layer, a second write layer, and a storage layer. The first write layer is disposed over the storage layer. The second write layer is disposed over the first write layer. The anisotropy field of the storage layer is greater than anisotropy field of the first write layer. The anisotropy field of the first write layer is greater than anisotropy field of the second write layer. The Curie temperature of the second write layer is greater than the Curie temperature of the first write layer. The Curie temperature of the first write layer is greater than the Curie temperature of the storage layer.
These and other features and advantages will be apparent from a reading of the following detailed description.
Before various embodiments are described in greater detail, it should be understood that the embodiments are not limiting, as elements in such embodiments may vary. It should likewise be understood that a particular embodiment described and/or illustrated herein has elements which may be readily separated from the particular embodiment and optionally combined with any of several other embodiments or substituted for elements in any of several other embodiments described herein.
It should also be understood that the terminology used herein is for the purpose of describing the certain concepts, and the terminology is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood in the art to which the embodiments pertain.
Unless indicated otherwise, ordinal numbers (e.g., first, second, third, etc.) are used to distinguish or identify different elements or steps in a group of elements or steps, and do not supply a serial or numerical limitation on the elements or steps of the embodiments thereof. For example, “first,” “second,” and “third” elements or steps need not necessarily appear in that order, and the embodiments thereof need not necessarily be limited to three elements or steps. It should also be understood that, unless indicated otherwise, any labels such as “left,” “right,” “front,” “back,” “top,” “middle,” “bottom,” “beside,” “forward,” “reverse,” “overlying,” “underlying,” “up,” “down,” or other similar terms such as “upper,” “lower,” “above,” “below,” “under,” “between,” “over,” “vertical,” “horizontal,” “proximal,” “distal,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. It should also be understood that the singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
It is understood heat assisted magnetic recording (HAMR) media may include both granular magnetic layers and continuous magnetic layers. Granular layers include grains that are segregated in order to physically and magnetically decouple the grains from one another. Segregation of the grains may be done, for example, with formation of oxides at the boundaries between adjacent magnetic grains. As such, the segregated magnetic grains form a granular layer. When multiple granular layers stacked together they form a columnar structure, where the magnetic alloys are hetero-epitaxially grown into columns while the oxides segregate into grain (column) boundaries. HAMR media may include both granular layers and continuous layers. In various embodiments, continuous layers include zero or much less segregation materials than found in the granular layers.
Information is written to the HAMR media at elevated temperatures close to the Curie temperature of the media. As the HAMR media is cooled down from the Curie temperature to the write temperature, e.g., 675 K, the anisotropy fields of the grains are still small enough such that grains under the write pole align with the magnetic field direction of the write pole. The grains are further cooled down to room temperature, e.g., 300 K, to permanently store information in the grains. Unfortunately, the storage layer used for HAMR media has a small magnetic moment and the Zeeman energy is insufficient to keep the grains from switching back to undesired states. Moreover, grains have variations, e.g., 3-5%, thus impacting the Curie temperature and the write temperature of the HAMR media that results in significant transition noise. Furthermore, even at lower temperatures, e.g., 550 K, grains with smaller volume are susceptible to erase after write and squeeze. Accordingly, a HAMR media with improved media recording performance and areal density is desired.
In some embodiments, a HAMR media includes a first write layer, a second write layer, and a storage layer. The first write layer is disposed over the storage layer. The second write layer is disposed over the first write layer. The anisotropy field of the storage layer is greater than anisotropy field of the first write layer. The anisotropy field of the first write layer is greater than anisotropy field of the second write layer. The Curie temperature of the second write layer is greater than the Curie temperature of the first write layer. The Curie temperature of the first write layer is greater than a Curie temperature of the storage layer. In other words, the HAMR media with anisotropy field gradient is formed with increasing anisotropy field from the uppermost write layer toward the bottommost storage layer. Moreover, the HAMR media with Curie temperature gradient is formed with decreasing Curie temperature from the uppermost write layer toward the bottommost storage layer.
Accordingly, magnetization of the uppermost write layer is oriented with the external magnetic field at writing temperature, e.g., lower than the layer's Curie temperature. Once the HAMR media cools down, the magnetization of subsequent layers is similarly oriented with the external magnetic field with assistance from previously oriented layers, e.g., uppermost write layer, etc., until the magnetization of the bottommost storage layer is oriented with the external magnetic field. In other words, the magnetization of each layer starting from the uppermost write layer has a cascading effect which assists the external magnetic field in orienting subsequent layers, e.g., subsequent write layers, subsequent storage layer(s), etc. The magnetization orientation of the storage layer, e.g., bottommost storage layer, is maintained once the HAMR media is cooled to the room temperature, e.g., 300 K.
It is appreciated that in some embodiments, a thermal exchange control layer (TECL) may be used, as described in patent application Ser. No. 15/466,798, which is incorporated herein by reference in its entirety. Coupling and decoupling between the storage layer and the write layer, using the thermal exchange control layer, during the heating and cooling process to write information in the storage layer, decouples the noise of the write layer from that of the storage layer, thereby reducing the overall noise once the HAMR media is returned to a temperature below the Curie temperature. It is appreciated that the Curie temperature of the thermal exchange control layer is lower than the Curie temperature of the storage layer which has a lower Curie temperature than the Curie temperature of the write layer. Thus, DC signal to noise ratio (SNR) and transition SNR are improved.
In some embodiments, the exchange coupled composite (ECC) of the HAMR media may be improved by inserting break layers between the write layers or a subset thereof. In some embodiments, the ECC of the HAMR media may be improved by inserting break layers between the storage layers or a subset thereof. According to some embodiments, the break layer may include nonmagnetic material. Furthermore, it is appreciated that the break layer may partially or completely couple and decouple the write layers and the storage layer during the heating process of writing information that is followed by the cooling process. Break layers may assist in further tuning the exchange coupling composite interaction between the write layers. In some embodiments, the break layer(s) may be weakly magnetic.
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According to some embodiments, each write layer, e.g., write layer 120, . . . , 124, may include material such as FePtX, FeCoPtX, FePdX, FeCoPdX, CoPtX, CoCrPtX, CoFePtX, CoCrX, FeCoX, or alloy thereof, etc. In some embodiments, the write layers include X is Ta, Mo, Si, Cu, Ag, Mn, Au, Ge, Hf, Zr, Ti, V, W, Fe, Ni, Oxide, Ru, Rh, Cr, B, BN, WO3, Ta2O5, SiO2, CrO3, CoO, TiO, etc.
It is appreciated that the write layers 120, . . . , 124 may be a continuous layer or one or more granular layers. For example, the write layer 120 may include grain decoupling material, e.g., C, Oxide such as B2O3, TaO5, TiO3, WO3, SiO2, Carbide such as SiC, BC, TiC, TaC, Nitride such as BN, SiN, TiN, etc., or any combination thereof.
It is appreciated that the storage layer 110 and the write layer 120-124 form an anisotropy field gradient that increases in value from the write layers toward the storage layer. In other words, the anisotropy field of the storage layer 110 is greater than the anisotropy field of the write layer 120. The anisotropy field of the write layer 120 is greater than or equal to the anisotropy field of the write layer 121. The anisotropy field of the write layer 121 is greater than or equal to the anisotropy field of the write layer 122. The anisotropy field of the write layer 122 is greater than or equal to the anisotropy field of the write layer 123. The anisotropy field of the write layer 123 is greater than or equal to the anisotropy field of the write layer 124.
It is appreciated that the storage layer 110 and the write layer 120-124 form a Curie temperature gradient that decreases in value from the write layers toward the storage layer. In other words, the Curie temperature of the storage layer 110 is smaller than the Curie temperature of the write layer 120. The Curie temperature of the write layer 120 is less than the Curie temperature of the write layer 121. The Curie temperature of the write layer 121 is less than the Curie temperature of the write layer 122. The Curie temperature of the write layer 122 is less than the Curie temperature of the write layer 123. The Curie temperature of the write layer 123 is less than the Curie temperature of the write layer 124. It is appreciated that in a HAMR media where Fe and/or FePt is used, use of Co can increase the Curie temperature. As such, higher amount of Co may be used for upper write layers in comparison to the lower write layers and the storage layer. Other similar components or compositions may be used to create the gradient, as described above.
It is appreciated that in order to form the anisotropy field and the Curie temperature gradient, as described above, the write layers have different compositions. For example, in some embodiments, the write layer 120 is different from the write layer 122, the write layer 120 is different from write layer 121 which are both different from the write layer 122, etc.
It is appreciated that in some embodiments, the storage layer 110 and the write layer 120-124 may also form magnetization gradient that decreases in value from the write layers toward the storage layer. In other words, magnetization of the storage layer 110 is smaller than the magnetization of the write layer 120. The magnetization of the write layer 120 is less than the magnetization of the write layer 121. The magnetization of the write layer 121 is less than the magnetization of the write layer 122. The magnetization of the write layer 122 is less than the magnetization of the write layer 123. The magnetization of the write layer 123 is less than the magnetization of the write layer 124.
When the media starts cooling down the stability and the alignment of the magnetization of the write layers and the storage layer are maintained until the freezing temperature (temperature at which the magnetization of the storage layer cannot be switched by the external magnetic field) is reached. It is appreciated that the magnetic orientation of the write layers and the magnetic orientation of the storage layer is maintained at freezing temperature, therefore retaining (storing) information therein.
It is appreciated that a thickness of the storage layer 110 may range between 1-15 nm. (inclusive). In some embodiments, a thickness of each write layer, e.g., write layer 124, write layer 123, . . . , write layer 120, may range from 0.1-5 nm (inclusive). It is appreciated that the write layers may have different thicknesses from one another. For example, a thickness of the write layer 124 may be different from the thickness of the write layer 123, etc.
Referring now to
It is appreciated that the break layers may be nonmagnetic according to some embodiments. For example, the break layers 131, . . . , 134 may include FeX, wherein X is Co, Cr, Oxide, Nitride, C, B, etc., and where the composition of X is selected such that FeX is nonmagnetic. In some embodiments, the break layers may include FeCoX where X is Cr, Oxide, Nitride, C, B, etc., where the composition of X is selected such that FeCoX is nonmagnetic. The break layers 131, . . . , 134 may further tune the ECC interaction between the write layers, e.g., write layer 120, . . . , 124. In some embodiments, the break layers and variation in their thickness, composition, growing condition, etc., may affect the intensity and/or directionality of the exchange interaction among the write layers that are magnetic, providing extra degrees of freedom for the ECC interaction.
It is appreciated that the break layers 131, . . . , 134 may be continuous layer or one or more granular layers. For example, the break layers 130, . . . , 134 may include grain decoupling material, e.g., C, carbide such as SiC, BC, TiC, TaC, etc., nitride such as BN, SiN, TiN, TaN, etc., oxide such as SiO2, B2O3, Ta2O5, TiO2, WO3, TaO5, TiO3, etc., or any combination thereof. According to some embodiments, the break layers 131, . . . , 134 maintain the granular structures, magnetization orientation and anisotropy between the storage layer 110 to the write layers 120, . . . , 124.
It is appreciated that in some embodiments, the HAMR media 100B further includes a thermal exchange control layer (TECL) 130. TECL 130 may be disposed between the bottommost write layer 120 and the uppermost storage layer 110. The Curie temperature of the TECL 130 is lower than the write layer 124. In fact, the TECL 130 may have a Curie temperature that is lower than all of the write layers 120-124 as well as the storage layer 110. TECL 130 partially turns the vertical exchange coupling between the write layer 120 and the storage layer 110 on and off during write process and cooling, wherein the partial turn on and off by the thermal exchange control layer suppresses noise. TECL may be substantially similar to the TECL described in patent application number 15/466,798 that is incorporated herein by reference in its entirety.
It is appreciated that in some embodiments, instead of using TECL 130 a break layer similar to break layers 131, . . . , 134 may be used. In some embodiments, no break layer and no thermal exchange control layer is used. Furthermore, it is appreciated that the use of the TECL 130 and/or break layers 131, . . . , 134 in the specific position within the HAMR media is exemplary and not intended to limit the scope of the embodiments. For example, the TECL 130 may be positioned between two write layers or it may be positioned between two storage layers. Moreover, a break layer may be positioned between the bottommost write layer and the uppermost storage layer. As such, use of the break layers and/or the thermal exchange control layer, as described, is for illustrative purposes and is not intended to limit the scope of the embodiments.
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This process repeats itself and cascades its way through the remaining write layers 120-122 and the storage layer 110. For example, referring now to
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The HAMR media 300A includes storage layer 310-312, e.g., FePt or an alloy thereof. For example, the storage layer 310 may be FePtX and the storage layer 312 may be FePtY, where X and Y is Cu, Ag, Ni, Ru, Rh, or Mn and where X is different from Y or that the ratio of the composition is different if the storage layers all contain the same components. For example, the storage layer 310-312 may include FePt where Fe ranges between 40-65% and Pt ranges between 35-60%. In this embodiment, M storage layers are shown but it is appreciated that the number of storage layers are for illustrative purposes only and should not be construed as limiting the scope of the embodiments. It is appreciated that the storage layers 310-312 may be a continuous layer or one or more granular layers, as described with respect to
It is appreciated that the storage layers 310-312 and the write layer 120-124 form an anisotropy field gradient that increases in value from the write layers toward the storage layers. In other words, the anisotropy field of the storage layer 310 is greater than the anisotropy field of the storage layer 312. Moreover, the anisotropy field of the storage layer 312 is greater than the anisotropy field of the write layer 120. The anisotropy field of the write layer 120 is greater than or equal to the anisotropy field of other write layers, e.g., write layer 124, as described above in
It is appreciated that the storage layers 310-312 and the write layer 120-124 form a Curie temperature gradient that decreases in value from the write layers toward the storage layers. In other words, the Curie temperature of the storage layer 310 is smaller than the Curie temperature of the storage layer 312. Similarly, the Curie temperature of the storage layer 312 is smaller than the Curie temperature of the write layer 120. The Curie temperature of the write layer 120 is less than the Curie temperature of other write layers, e.g., write layer 124, as described above in
Because of the anisotropy field gradient and the Curie temperature gradient that is formed using the write layers 120-124 and the storage layers 310-312, each layer assists the external magnetic field to orient the magnetic field of the remaining layers, as described above. For example, the magnetic fields of the write layers 120-124 are oriented as described in
When the media starts cooling down the stability and the alignment of the magnetization of the write layers and the storage layer are maintained until the freezing temperature (temperature at which the magnetization of the storage layer cannot be switched by the external magnetic field) is reached. The write layers may be chosen from material such that their magnetic properties remain substantially the same at writing temperature of the storage layer 110 therefore achieving substantial anisotropy field and magnetization variation in the system. It is appreciated that the magnetic orientation of the write layers and the magnetic orientation of the storage layer is maintained at freezing temperature, therefore retaining (storing) information therein.
Referring now to
It is appreciated that any two layers, e.g., any two write layers, any two storage layers, any write layer and storage layer, may be separated from one another using a break layer, as described in
It is appreciated that the break layers may be nonmagnetic according to some embodiments. For example, the break layers may include FeX, wherein X is Co, Cr, Oxide, Nitride, C, B, etc., and where the composition of X is selected such that FeX is nonmagnetic. In some embodiments, the break layers may include FeCoX where X is Cr, Oxide, Nitride, C, B, etc., where the composition of X is selected such that FeCoX is nonmagnetic. The break layers may further tune the ECC interaction between the storage layers, e.g., storage layer 310, . . . , 312. In some embodiments, the break layers and variation in their thickness, composition, growing condition, etc., may affect the intensity and/or directionality of the exchange interaction among the write layers that are magnetic, providing extra degrees of freedom for the ECC interaction.
It is appreciated that the break layers may be continuous layers or one or more granular layers. For example, the break layers may include grain decoupling material, e.g., C, carbide such as SiC, BC, TiC, TaC, etc., nitride such as BN, SiN, TiN, TaN, etc., oxide such as SiO2, B2O3, Ta2O5, TiO2, WO3, TaO5, TiO3, etc., or any combination thereof. According to some embodiments, the break layers maintain the granular structures, magnetization orientation and anisotropy between the storage layers 310-312 to the write layers 120-124.
It is appreciated that each break layer may have a different composition and/or thickness than other break layers. In some embodiments, at least two break layers have a different composition from one another. In some embodiments, at least two break layers have a different thickness from one another.
Referring now to
At step 450, the process is repeated for other write layers. In other words, other write layers are similarly aligned with the external magnetic field using previously aligned write layers. The previously aligned write layers assist the external magnetic field to orient the magnetic orientation of other write layers that have a higher anisotropy field and lower Curie temperature. The process is repeated until at step 460, the magnetic field orientation of the storage layers are aligned with that of the write layers and the external magnetic field. It is appreciated that the storage layers also have anisotropy field gradient and Curie temperature gradient similar to that of the writing layers. In other words, the upper storage layers, closer to the writing layers, have a smaller anisotropy field and higher Curie temperature in comparison to the lower storage layers. At freezing temperature, the apparatus is stable enough that the magnetic field orientation of the storage layer will not change in absence of the external magnetic field. As such, at step 470, the external magnetic field may be removed and the magnetic field orientation of the write layers and the storage layer may be maintained.
Accordingly, the gradient for the anisotropy field and Curie temperature of the write layers and the storage layers enables the write layer with lower anisotropy field and higher Curie temperature to pin other write layers and storage layers, with higher anisotropy field and lower Curie temperature, in presence of external magnetic field. The pinned write layers may subsequently pin other layers until the magnetic orientation of the storage layers is aligned with that of the external magnetic field. Because the apparatus has cooled off enough to reach the freezing temperature, the magnetic orientations of the write layers and the storage layer are maintained in absence of the external magnetic field. Accordingly, a HAMR media with improved media recording performance and areal density is provided. Moreover, DC signal to noise ratio (SNR) and transition SNR is improved.
While the embodiments have been described and/or illustrated by means of particular examples, and while these embodiments and/or examples have been described in considerable detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the embodiments to such detail. Additional adaptations and/or modifications of the embodiments may readily appear to persons having ordinary skill in the art to which the embodiments pertain, and, in its broader aspects, the embodiments may encompass these adaptations and/or modifications. Accordingly, departures may be made from the foregoing embodiments and/or examples without departing from the scope of the concepts described herein. The implementations described above and other implementations are within the scope of the following claims.
