Patent Application
20070253103
The present invention generally relates to sputter targets and magnetic recording media. In particular, the invention relates to corrosion-resistant soft magnetic alloy based sputter targets, and the use of such targets to deposit a soft magnetic film for application in perpendicular magnetic recording media, and on magnetic recording heads.
To satisfy the continual demand for even greater data storage capacities, higher density magnetic recording media are required. Of the approaches to achieve this high data density, perpendicular magnetic recording (PMR) by far appears to be the most promising. In contrast to longitudinal magnetic recording, the magnetic data recording layer of the recoding media has its magnetic lines directed perpendicular to the axis of the recording media in perpendicular magnetic recording. Also, in perpendicular magnetic recording, a higher writing field can be obtained by using a soft magnetic under-layer (SUL) beneath the magnetic data recording layer.
For example, a single-pole recording head and a corresponding magnetic recording media having a soft underlayer enables write fields in excess of double of that which is available for conventional longitudinal recording. Accordingly, acting as a magnetic mirror, a SUL effectively doubles the recording layer thickness, facilitating stronger read-out signals. These soft under layers are magnetically soft (with High magnetic induction (Bs), high permeability (μe), low coercivity (Hc)) alloys, such as alloys of Co, Ni and Fe. Similar magnetically soft layers based on these alloys are also used as components in writer pole and reader sensor elements contained in magnetic recording head designs.
Although higher writing fields and performance can be achieved in PMR applications using magnetically soft alloys as described above, such alloys can have a high propensity for corrosion, thereby potentially causing severe reliability issues in both the magnetic recording media and in the recording head during hard disk drive operations.
The present invention solves the foregoing problems by providing corrosion-resistant soft magnetic alloy based sputter targets for use to deposit a corrosion-resistant soft magnetic underlayer in magnetic recording media, and soft magnetic layers on magnetic recording heads, for reliable, high performance perpendicular magnetic recording.
In accordance with one embodiment of the present invention, a magnetic recording medium having a corrosion-resistant soft magnetic underlayer is provided. Specifically, a magnetic recording medium is provided that includes a substrate, an underlayer deposited above the substrate, the underlayer being comprised of a magnetically soft alloy containing at least one soft ferromagnetic element and at least one corrosion inhibitor element that is selected from the group consisting of chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), copper (Cu), nickel (Ni), manganese (Mn), nitrogen (N), titanium (Ti), niobium (Nb), silicon (Si), tantalum (Ta), and aluminum (Al), and a magnetic data recording layer deposited above the underlayer.
In another embodiment, the present invention is a magnetic recording head that includes a writer pole and a reader sensor, wherein the writer pole and the reader sensor include an soft magnetic film disposed above a substrate, the soft magnetic film comprised of a magnetically soft alloy containing at least one soft ferromagnetic element and at least one corrosion inhibitor element that is selected from the group consisting of chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), copper (Cu), nickel (Ni), manganese (Mn), nitrogen (N), titanium (Ti), niobium (Nb), silicon (Si), tantalum (Ta), and aluminum (Al).
According to a further embodiment, the present invention is directed to a method of manufacturing a magnetic recording medium, including a first sputtering step of sputtering an underlayer above a substrate from a first sputter target that is comprised of a magnetically soft alloy containing at least one soft ferromagnetic element and at least one corrosion inhibitor element that is selected from the group consisting of chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), copper (Cu), nickel (Ni), manganese (Mn), nitrogen (N), titanium (Ti), niobium (Nb), silicon (Si), tantalum (Ta), and aluminum (Al), and a second sputtering step of sputtering a magnetic data recording layer above the underlayer from a second sputter target.
According to yet another embodiment, the present invention is directed to a sputter target including a magnetically soft alloy containing at least one soft ferromagnetic element and at least one corrosion inhibitor element that is selected from the group consisting of chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), copper (Cu), nickel (Ni), manganese (Mn), nitrogen (N), titanium (Ti), niobium (Nb), silicon (Si), tantalum (Ta), and aluminum (Al).
In a further embodiment, the invention is directed to a method of manufacturing a magnetic recording head having a writer pole and a reader sensor, the method including a sputtering step of sputtering a magnetically soft film above a substrate deposited on at least one of the writer pole and the reader sensor, the magnetically soft film being sputtered from a sputter target that is comprised of a magnetically soft alloy containing at least one soft ferromagnetic element and at least one corrosion inhibitor element that is selected from the group consisting of chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), copper (Cu), nickel (Ni), manganese (Mn), nitrogen (N), titanium (Ti), niobium (Nb), silicon (Si), tantalum (Ta), and aluminum (Al).
In the above embodiments, the at least one soft ferromagnetic element is preferably selected from the group consisting of cobalt (Co), iron (Fe) and nickel (Ni), and the at least one corrosion inhibitor element is selected from a subset of the above-listed group of inhibitor elements depending on the selected ferromagnetic element. In addition, the amount of the inhibitor element included in the magnetically soft alloy is limited up to a predetermined limit of atomic ratio, where the predetermined atomic ratio limit is determined according to which soft ferromagnetic element(s) is selected and on which inhibitor element is selected.
In this manner, a magnetically soft alloy is provided that has a high saturation magnetic induction (Bs) greater than 0.5 Tesla, a high permeability (μe) of greater than 10.0 at 1 KHz, and a low coercivity (Hc) of less than 8000 oestead.
Additional features and advantages of the invention will be set forth in the description below, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
In the following detailed description, numerous specific details are set forth to provide a full understanding of the present invention. It will be apparent, however, to one ordinarily skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the present invention.
The invention is generally directed to providing corrosion-resistant soft magnetic alloy based sputter targets for use to deposit a corrosion-resistant soft magnetic film layer as an underlayer in a perpendicular magnetic recording medium stack, and as a magnetically soft film layer on magnetic recording heads, for reliable, high performance magnetic recording. In this manner, magnetic recording media, and magnetic recording head components, are produced having a corrosion-resistant soft magnetic underlayer, resulting in higher write fields and in reliable, corrosion-resistant performance.
As mentioned above, underlayer 104 is deposited above the substrate 101, or above intervening optional low-level layers 102. Underlayer 104 is comprised of a corrosion-resistant soft magnetic alloy, as discussed in more detail herein. As seen in
In this manner, underlayer 104 of the present invention enables magnetic recording medium 100 to achieve reliable, high performance perpendicular magnetic recording (PMR) during operation of magnetic recording medium 100. Underlayer 104 acts as a magnetic mirror and effectively doubles the thickness of magnetic data recording layer 106, resulting in stronger readout signals from magnetic recording medium 100. Specifically, underlayer 104 is comprised of a corrosion-resistant soft magnetic alloy, which contains at least one or more soft ferromagnetic element, and at least one corrosion inhibitor element. In this regard, the soft ferromagnetic element(s) in the soft magnetic alloy is preferably one of, or any combination of, cobalt (Co), iron (Fe) and nickel (Ni), although other soft ferromagnetic elements can also be included in the soft magnetic alloy. In the present invention, the soft magnetic alloy also contains one or more corrosion inhibitor elements which are selected based on the soft ferromagnetic element(s) selected to be in the soft magnetic alloy. This is because some corrosion inhibitor elements are effective to resist corrosion in an alloy having certain selected soft ferromagnetic elements but not others.
Table 1, below, provides a list of corrosion inhibitor elements that can be used in the present invention to form the corrosion-resistant soft magnetic alloy used in conjunction with one or more of soft ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni). As mentioned above, the set of corrosion inhibitor elements that can be effectively used with each of the soft ferromagnetic elements are different, because some corrosion inhibitor elements work effectively with some soft ferromagnetic elements but not with others.
As seen in Table 1, a list of corrosion inhibitor elements is provided for each one of the soft ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni). In the present invention, the corrosion-resistant soft magnetic alloy includes one or more of soft ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni) and one or more of the corrosion inhibitor elements from the list in Table 1 corresponding to each ferromagnetic element included in the alloy.
For example, if the alloy contains cobalt (Co), then one or more of corrosion inhibitor elements chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), copper (Cu), and nickel (Ni) is selected to include in the alloy to provide corrosion resistant properties for the cobalt (Co) in the alloy. As seen in Table 1, each one of the listed corrosion inhibitor elements is associated with an upper limit of percentage of atomic ratio. This represents the upper limit of atomic ratio with respect to the corresponding ferromagnetic element for the amount of the particular corrosion inhibitor element included in the alloy. For example, an alloy containing cobalt (Co) along with the selected corrosion inhibitor element of tungsten (W) could have up to 15% of tungsten (W) by atomic ratio with respect to the amount of cobalt (Co) in the alloy. In other words, if the alloy contains one million atoms of cobalt (Co), then up to 150,000 atoms of tungsten (W) could be in the alloy. The upper limits are provided for the corrosion inhibitor elements in association with each of the soft ferromagnetic elements because the effectiveness of a corrosion inhibitor element is not increased when the corrosion inhibitor element is added into the alloy beyond that upper limit, and because the addition of the corrosion inhibitor element beyond the upper limit may affect the soft magnetic properties of the alloy.
As seen in Table 1, the corrosion inhibitor elements listed in Table 1 are different for each of the corresponding soft ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni). In this manner, the present invention provides combinations of soft magnetic alloys that can be used in underlayer 104 of magnetic recording medium 100, and for making sputter targets which are used to make underlayer 104. Turning to the other columns of Table 1, it can be seen that, if the alloy contains iron (Fe), then one or more of corrosion inhibitor elements chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), nickel (Ni), manganese (Mn), nitrogen (N), titanium (Ti), niobium (Nb), and silicon (Si) is selected to include in the alloy to provide corrosion resistant properties for the cobalt (Fe) in the alloy.
Similarly, if the alloy contains nickel (Ni), then one or more of corrosion inhibitor elements chromium (Cr), tungsten (W), molybdenum (Mo), carbon (C), copper (Cu). aluminum (Al), tantalum (Ta), titanium (Ti), niobium (Nb), and silicon (Si) is selected to include in the alloy to provide corrosion resistant properties for the cobalt (Ni) in the alloy. As mentioned above, the corrosion-resistant soft magnetic alloy of the present invention can also be comprised of two or more of soft ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni). For example the corrosion-resistant soft magnetic alloy can be a Co—Fe alloy, a Co—Ni alloy or a Co—Fe—Ni alloy, or any other possible combination of soft ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni). In such a case, one or more of the corrosion inhibitor elements can be selected from the respective column of Table 1 corresponding to each of the soft ferromagnetic elements included in the alloy. The amount of the selected corrosion inhibitor elements could can be included up to the atomic ratio limit provided in the column with respect to the amount of the ferromagnetic element for that column included in the alloy.
It can be appreciated upon review of Table 1 that a same corrosion inhibitor element, such as tungsten (W), can be used for all three ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni) in the case of a Co—Fe—Ni alloy. In such an example, the amount of tungsten (W) included in the alloy could include a separate amount of tungsten (W) up to the atomic ratio limit provided in Table 1 for each of cobalt (Co), iron (Fe) and nickel (Ni). In this manner, the desired soft magnetic properties of the soft magnetic alloy are maintained, and the appropriate amount of corrosion resistance is included in the alloy. Specifically, the corrosion resistant soft magnetic alloy provided for underlayer 104 of the present invention has a high saturation magnetic induction (Bs) greater than 0.5 Tesla, and has soft magnetic behavior with a high permeability (μe) of greater than 10.0 at 1 KHz, and with a low coercivity (Hc) of less than 8000 oestead.
The corrosion resistant soft magnetic alloy of underlayer 104 can also include other elements in addition to one or more of the soft ferromagnetic elements cobalt (Co), iron (Fe) and nickel (Ni), and one or more of the corrosion inhibitor elements listed in Table 1. The underlayer 104 of the present invention is either in a nanocrystalline form or an amorphous form. Accordingly, it may be desirable to include one or more nucleating agent to the corrosion resistant soft magnetic alloy in order to obtain nanocrystalline form in the soft magnetic alloy film of underlayer 104. In this regard, such nucleating agents can include one or more of the noble metals, such as copper (Cu), silver (Ag), and gold (Au), for example.
In the alternative, it may be desirable to include one or more glass-forming additives to the corrosion resistant soft magnetic alloy in order to obtain an amorphous form in the soft magnetic alloy film of underlayer 104. In this manner, it is possible for underlayer 104 to be comprised of a single magnetic domain. Such glass-forming additives can include one or more of the early transition elements, such as zirconium (Zr), hafnium (Hf), vanadium (V), tantalum (Ta), and niobium (Nb), for example, and the metalloids, such as boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te), for example. Known methods can be used to include one or more of such nucleating agents or glass-forming additives into the alloy.
The corrosion resistant soft magnetic alloy discussed above with respect to underlayer 104 of magnetic recording medium 100 can also be used to form a soft magnetic film layer in the components of a recording head for increased performance in a perpendicular magnetic recording (PMR) head.
In this regard,
As mentioned above, soft magnetic film layer 213 is deposited above the substrate 211, and is comprised of a corrosion-resistant soft magnetic alloy, as described above with respect to the corrosion-resistant soft magnetic alloy of underlayer 104 of magnetic recording medium 100 shown in
As seen in
In the example shown in
Next, a corrosion resistant soft magnetic alloy underlayer is sputtered above the substrate, or above low level layers if any were applied, from a corrosion resistant soft magnetic alloy sputter target (step 403). The corrosion resistant soft magnetic alloy sputter target is comprised of a corrosion-resistant soft magnetic alloy as described above with respect to
After the corrosion resistant soft magnetic alloy underlayer is applied in step 403, other underlayers or a seed layer may optionally be sputtered above the corrosion resistant soft magnetic alloy underlayer (step 404). At least one magnetic data recording layer is then sputtered above the corrosion resistant soft magnetic alloy underlayer (or above intervening underlayers or seed layer) from a different sputter target. (step 405). An additional protective layer or layers, such as a carbon (C) overcoat and/or a lubricant layer, are sputtered above the magnetic data recording layer in step 406, and the process ends (step 407). In alternate aspects, step 406 is omitted and no protective layer is sputtered onto the magnetic data recording layer. Of course, other steps can be added or omitted from the foregoing exemplary process to manufacture a magnetic recording medium without departing from the scope of the invention.
While the present invention has been particularly described with reference to the various figures and embodiments, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the invention in any way. For example, although sputter targets implementing the present invention may be round, square, rectangular, or any number of other shapes, such as rectilinear, solid or hollow cylindrical, or nearly any other shape. It is to be appreciated that changes and modifications may be made to the invention by one having ordinary skill in the art without departing from the spirit and scope of the invention.
