Patent Application
20150371666
The present disclosure relates to magnetic recording technology, and in particular, to a magnetic shield for a magnetic recording head that is stable and exhibits efficient antiparallel coupling performance.
Data storage media density has significantly increased over the last several decades. Thin film recording head technology has advanced to keep up with increasing data storage media density through the advent of technologies such as giant magnetoresistive (GMR), tunneling magnetoresistive (TMR), or perpendicular magnetic recording (PMR). Each of these magnetic recording technologies may incorporate a magnetic shield as a component of the completed magnetic recording head system. As the various recording head technologies target smaller and smaller bit sizes, increased magnetic shield domain stabilization is required to reduce magnetic noise. One method of managing magnetic shield domain stability is to incorporate an anti-ferromagnetic material to bias the shield into a desired magnetic orientation, creating an antiparallel composite shield configuration. In such a configuration, the thin film recording sensor is surrounded by a soft bias material, and a pair of ferromagnetic layers separated by a spacer layer are deposited thereon, such that the upper ferromagnetic layer is magnetically pinned to the lower ferromagnetic layer, but separated by the spacer. In this shield configuration, as the spacer layer thickness is increased, magnetic coupling performance decreases, effectively limiting the spacer thickness. However, at very thin spacer thicknesses, shield stability decreases due to irregular grain growth in the ferromagnetic layers surrounding the spacer. The irregular growth increases with multiple anneals of the shield, and thus shield stability decreases with multiple anneals. This constraint requiring the spacer to be thicker to avoid shield instability, but thinner to maintain a strong antiparallel coupling performance, effectively limits the effectiveness of the currently available magnetic shields.
Various embodiments are illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which:
The figures are not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the disclosed technology be limited only by the claims and the equivalents thereof.
In the following description, numerous specific details are set forth to provide a thorough understanding of various embodiment of the present disclosure. It will be apparent to one skilled in the art, however, that these specific details need not be employed to practice various embodiments of the present disclosure. In other instances, well known components or methods have not been described in detail to avoid unnecessarily obscuring various embodiments of the present disclosure.
As disclosed herein, a magnetic shield for a magnetic recording head may include a plurality of ferromagnetic layers, a buffer layer; and a spacer layer. For example, the ferromagnetic layers may be NiFe, the buffer layer may be CoFeB, and the spacer layer may be Ru. In some examples, the buffer layer is between 5 Angstroms and 50 Angstroms thick. In one example, the spacer layer is not more than 10 Angstroms thick
Some embodiments of the disclosure provide a process for manufacturing a magnetic shield wherein the process includes depositing a plurality of ferromagnetic layers, depositing a buffer layer, and depositing a spacer layer. For example, a first ferromagnetic layer may be deposited on a magnetic sensor and soft bias layers, a buffer layer may be deposited on the first ferromagnetic layer, a second ferromagnetic layer may be deposited on the buffer layer, a spacer layer may be deposited on the second ferromagnetic layer, and a third ferromagnetic layer may be deposited on the spacer layer. In some examples, the ferromagnetic layers are NiFe. In some examples, the buffer layer is an amorphous CoFeB and the spacer layer is Ru. For example, the ferromagnetic layers may magnetically couple through the buffer layer and the spacer layer. In some embodiments, one or more antiferromagnetic layers are deposited on top of the magnetic shield.
Magnetic recording sensor 110 may be either a giant magnetoresistive (GMR), tunneling magnetoresistive (TMR), or perpendicular magnetic recording (PMR) sensor, or other magnetic recording sensor as would be known in the art. The magnetic recording head may be a read head or a write head. In some examples, the magnetic shield may also be formed on both sides of the magnetic recording head. In other examples, the magnetic shield may be formed on a magnetic write head. The magnetic shield technology disclosed herein is not dependent on the method or form of the magnetic read or write head.
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In some example magnetic shields, the buffer layer 135 may comprise Co, Fe, and B in varying ratios to increase magnetic coupling efficiency through the ferromagnetic layers. For example, the buffer layer 135 may comprise CoxFeyBz where x, y, and z represent an atomic percent of the total number of atoms in the buffer layer such that, for a total of 100 atomic percent, z=100−x−y and z<35 atomic percent. In several embodiments, buffer layer 135 may be amorphous (e.g. an amorphous CoFeB layer).
Some example buffer layers may comprise at least 70 atomic percent of Co, not more than 10 atomic percent of Fe, and not more than 20 atomic percent of B. Other example buffer layers may comprise between 35 atomic percent and 45 atomic percent Co, between 35 atomic percent and 45 atomic percent Fe, and between 15 atomic percent and 25 atomic percent B. Other example buffer layers may comprise between 0 atomic percent and 50 atomic percent Fe, between 10 atomic percent and 30 atomic percent B, and Co. In other examples, the buffer layer 135 may comprise Co and B, but without any, or only trace amounts of Fe.
In some embodiments of the disclosure, a buffer layer 135 as thin as 3 Angstroms provides sufficient magnetic coupling of the ferromagnetic layers with sufficient reduction of NiFe grain growth. In other embodiments, a buffer layer 135 as thick as 50 Angstroms provides sufficient magnetic coupling of the ferromagnetic layers with sufficient reduction of NiFe grain growth. Other buffer layer thicknesses may be used, as would be known to one of skill in the art, to provide sufficient magnetic and thermal stability by reducing NiFe grain growth while still providing sufficient magnetic coupling of the ferromagnetic layers.
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Although described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the application, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present application should not be limited by any of the above-described exemplary embodiments.
The terms “over,” “under,” “between,” and “on” as used herein refer to a relative position of one media layer with respect to other layers. As such, for example, one layer disposed over or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer disposed between two layers may be directly in contact with the two layers or may have one or more intervening layers. In contrast, a first layer “on” a second layer is in contact with that second layer. Additionally, the relative position of one layer with respect to other layers is provided assuming operations are performed relative to a substrate without consideration of the absolute orientation of the substrate.
Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.
The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations.
Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.
