1. Field of the Invention
The present invention relates generally to magnetoresistive (MR) sensor elements employed within magnetic data storage and retrieval. More particularly, the present invention relates to enhanced magnetoresistive (MR) resistivity sensitivity anisotropic magnetoresistive (MR) sensor elements employed within magnetic data storage and retrieval.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is defined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein.
Within the general category of magnetoresistive (MR) sensor elements, anisotropic magnetoresistive (MR) sensor elements are presently of considerable interest insofar as anisotropic magnetoresistive (MR) sensor elements have found widespread use in various magnetic data storage and transduction applications, and in particular digitally encoded magnetic data storage and transduction applications. Within the context of the present disclosure, anisotropic magnetoresistive (MR) sensor elements are intended as magnetoresistive (MR) sensor elements fabricated employing either a single magnetoresistive (MR) sensing layer or a multiplicity of magnetoresistive (MR) sensing layers which are separated by dielectric spacer layers, and where a magnetoresistive (MR) effect within such an anisotropic magnetoresistive (MR) sensor element derives from magnetically encoded data flux perturbation of a magnetically aligned domain within either the single magnetoresistive (MR) sensing layer or the multiplicity of magnetoresistive (MR) sensing layers. Such anisotropic magnetoresistive (MR) sensor elements include, but are not limited to single stripe magnetoresistive (SSMR) sensor elements, soft adjacent layer (SAL) magnetoresistive (MR) sensor elements and dual stripe magnetoresistive (DSMR) sensor elements.
Within magnetoresistive (MR) sensor element fabrication, including but not limited to anisotropic magnetoresistive (MR) sensor element fabrication, it is particularly desirable to fabricate magnetoresistive (MR) sensor elements with enhanced levels of magnetoresistive (MR) resistivity sensitivity. For purposes of clarity, and within the context of the present disclosure, magnetoresistive (MR) resistivity sensitivity is intended as a measure of proportion of resistance change normalized to an absolute resistance of a magnetoresistive (MR) sensor element (i.e. dR/R) when measuring a magnetic signal within a magnetic data storage medium while employing the magnetoresistive (MR) sensor element. The magnetoresistive (MR) resistivity sensitivity of a magnetoresistive (MR) sensor element is alternatively known as the magnetoresistive (MR) coefficient of the magnetoresistive (MR) sensor element. Magnetoresistive (MR) sensor elements exhibiting enhanced magnetoresistive (MR) resistivity sensitivity are desirable within the art of magnetoresistive (MR) sensor element fabrication since such enhanced magnetoresistive (MR) resistivity sensitivity clearly inherently allows for detection within a magnetic data storage medium of weaker magnetic signals with increased linear density and thus also inherently allows for an increased areal density of the magnetic data storage medium within a magnetic data storage enclosure which employs the magnetoresistive (MR) sensor element which exhibits the enhanced magnetoresistive (MR) resistivity sensitivity.
It is thus towards the goal of forming for use within magnetic data storage and retrieval anisotropic magnetoresistive (MR) sensor elements, such as but not limited to single stripe magnetoresistive (SSMR) sensor elements, soft adjacent layer (SAL) magnetoresistive (MR) sensor elements and dual stripe magnetoresistive (DSMR) sensor elements, with enhanced magnetoresistive (MR) resistivity sensitivity, that the present invention is directed.
Various magnetic sensor elements, including but not limited to anisotropic magnetoresistive (MR) sensor elements, which possess desirable properties have been disclosed within the art of magnetic sensor element fabrication, including but not limited to anisotropic magnetoresistive (MR) sensor element fabrication.
For example, Goubau et al., in U.S. Pat. No. 5,268,806, disclose a magnetoresistive (MR) sensor element having a conductor lead structure which remains stable not only during processing when fabricating the magnetoresistive (MR) sensor element, but also over the useful operational life of the magnetoresistive (MR) sensor element. The magnetoresistive (MR) sensor element employs a conductor lead structure comprising: (1) a seed layer contacting a magnetoresistive (MR) layer within the magnetoresistive (MR) sensor element, where the seed layer is formed from a material selected from the group consisting of chromium, tungsten, an alloy of titanium and tungsten, and an alloy of tantalum and tungsten, and where the seed layer has a body centered cubic lattice structure; and (2) a conductor layer formed upon the seed layer, where the conductor layer is formed of tantalum, and where the conductor layer also has a body centered cubic lattice structure.
In addition, Fontana Jr. et al., in U.S. Pat. No. 5,701,223, disclose a spin valve magnetoresistive (SVMR) sensor element with improved magnetoresistive (MR) properties, such as an enhanced magnetoresistive (MR) resistivity sensitivity, as well as improved chemical properties, such as an enhanced corrosion resistance of an antiferromagnetic pinning material layer within the spin valve magnetoresistive (SVMR) sensor element. The spin valve magnetoresistive (SVMR) sensor element realizes the foregoing objects by employing when forming the spin valve magnetoresistive (SVMR) sensor element: (1) a pair of anti-parallel antiferromagnetically biased ferromagnetic material layers separated by a non-magnetic conductor spacer layer to provide a composite pinned ferromagnetic layer within the spin valve magnetoresistive (SVMR) sensor element, in conjunction with; (2) a pinning material layer formed of a pinning material selected from the group consisting of nickel oxide, nickel-cobalt alloy oxides and iron-manganese-chromium alloys.
Further, Lee et al., in U.S. Pat. No. 5,731,936, disclose an anisotropic magnetoresistive (MR) sensor element, such as a soft adjacent layer (SAL) magnetoresistive (MR) sensor element, with an enhanced magnetoresistive (MR) resistivity sensitivity as well as an enhanced thermal stability. The anisotropic magnetoresistive (MR) sensor element employs a nickel-iron-chromium alloy or a nickel-chromium alloy spacer layer adjoining a nickel-iron alloy magnetoresistive (MR) layer formed within the anisotropic magnetoresistive (MR) sensor element.
Still further, Chang et al., in U.S. Pat. No. 5,763,108, disclose a high saturation magnetization magnetic material for use when fabricating a magnetic head, and a magnetic head fabricated employing the high saturation magnetization magnetic material for use when fabricating the magnetic head. The high saturation magnetization magnetic material has an elemental composition comprising about 40 to about 60 weight percent iron, about 40 to about 60 weight percent nickel and about 0.002 to about 1 percent tin.
Finally, Lin, in U.S. Pat. No. 5,768,071, discloses a spin valve magnetoresistive (SVMR) sensor element having an improved magnetic stability of a pinned ferromagnetic layer within the spin valve magnetoresistive (SVMR) sensor element. The spin valve magnetoresistive (SVMR) sensor element realizes the foregoing object by employing when forming the spin valve magnetoresistive (SVMR) sensor element a discontinuous nonmagnetic interlayer interposed between an antiferromagnetic pinning material layer and the pinned ferromagnetic layer within the spin valve magnetoresistive (SVMR) sensor element.
Desirable in the art of magnetoresistive (MR) sensor element fabrication are additional methods and materials which may be employed for forming with enhanced magnetoresistive (MR) resistivity sensitivity anisotropic magnetoresistive (MR) sensor elements, including in particular dual stripe magnetoresistive (DSMR) sensor elements.
It is towards the foregoing object that the present invention is directed.
A first object of the present invention is to provide a method for forming an anisotropic magnetoresistive (MR) sensor element, along with the anisotropic magnetoresistive (MR) sensor element formed employing the method.
A second object of the present invention is to provide a method and an anisotropic magnetoresistive (MR) sensor element in accord with the first object of the present invention, where the anisotropic magnetoresistive (MR) sensor element has an enhanced magnetoresistive (MR) resistivity sensitivity.
A third object of the present invention is to provide a method and an anisotropic magnetoresistive (MR) sensor element in accord with the first object of the present invention and the second object of the present invention, which method is readily commercially implemented.
In accord with the objects of the present invention, there is provided by the present invention a method for forming an anisotropic magnetoresistive (MR) sensor element, as well as the anisotropic magnetoresistive (MR) sensor element formed in accord with the method. To practice the method of the present invention, there is first provided a substrate. There is then formed over the substrate a seed layer, where the seed layer is formed of a magnetoresistive (MR) resistivity sensitivity enhancing material selected from the group consisting or nickel-chromium alloys and nickel-iron-chromium alloys. There is then formed over the seed layer a nickel oxide material layer. There is then formed over the nickel oxide material layer a magnetoresistive (MR) ferromagnetic layer.
The method of the present invention contemplates an anisotropic magnetoresistive (MR) sensor element fabricated in accord with the method of the present invention.
The present invention provides a method for forming an anisotropic magnetoresistive (MR) sensor element, and the anisotropic magnetoresistive (MR) sensor element formed employing the method, where the anisotropic magnetoresistive (MR) sensor element has an enhanced magnetoresistive (MR) resistivity sensitivity. The method of the present invention realizes the foregoing object by employing when forming the anisotropic magnetoresistive (MR) sensor element: (1) a seed layer formed of a magnetoresistive (MR) resistivity sensitivity enhancing material selected from the group consisting of nickel-chromium alloys and nickel-iron-chromium alloys, in turn having formed thereover; (2) a nickel oxide material layer, in turn having formed thereover; (3) a magnetoresistive (MR) ferromagnetic layer. While it is not entirely clear why an anisotropic magnetoresistive (MR) sensor element formed in accord with the present invention exhibits an enhanced magnetoresistive (MR) resistivity sensitivity, it is nonetheless clear that an anisotropic magnetoresistive (MR) sensor element formed in accord with the present invention exhibits an enhanced magnetoresistive (MR) resistive sensitivity in comparison with an analogous anisotropic magnetoresistive (MR) sensor formed otherwise in accord with the present invention, but absent a nickel oxide material layer formed interposed between: (1) a seed layer formed of a magnetoresistive (MR) resistivity sensitivity enhancing material selected from the group consisting of nickel-chromium alloys and nickel-iron-chromium alloys; and (2) a magnetoresistive (MR) ferromagnetic layer.
The method of the present invention is readily commercially implemented. The present invention employs methods and materials as are generally known in the art of magnetoresistive (MR) sensor element fabrication but employed within the context of specific locations and limitations within an anisotropic magnetoresistive (MR) sensor element to provide the present invention. Since it is a novel ordering and use of methods and materials which at least in part provides the present invention, rather than the existence of methods and materials which provides the present invention, the method of the present invention is readily commercially implemented.