Patent Application
20070211392
The present invention relates in general to magnetoresistive devices, and more particularly to magnetoresistive devices that use exchange-coupled antiferromagnetic/ferromagnetic (AF/F) structures, such as current-in-the-plane (CIP) read heads and current-perpendicular-to-the-plane (CPP) magnetic tunnel junctions and read heads.
In magnetic disk drives, data is written and read by magnetic transducers called “heads.” The magnetic disks are rotated at high speeds, producing a thin layer of air called an air bearing (AB). The read and write heads are supported over the rotating disk by an air bearing surface (ABS), where they either induce or detect flux on the magnetic disk, thereby either writing or reading data. Layered thin film structures are typically used in the manufacture of read and write heads. In write heads, thin film structures provide high magnetic flux to produce recorded magnetic bits on a recording disk with high areal density, which is the amount of data stored per unit of disk surface area, and in read heads they provide high resolution.
Some read heads in magnetic disk drives use so-called current-in-plane (CIP) magnetoresistive principles, a common example of which is a device that uses an exchange-coupled structure and that is known as a spin-valve (SV) type of giant magnetoresistive (GMR) sensor. The SV GMR head has two ferromagnetic layers separated by a very thin nonmagnetic conductive spacer layer, typically copper, wherein the electrical resistivity for the sensing current in the plane of the layers depends upon the relative orientation of the magnetizations in the two ferromagnetic layers. The direction of magnetization or magnetic moment of one of the ferromagnetic layers (the “free” layer or stack) is free to rotate in the presence of the magnetic fields from the recorded data, while the other ferromagnetic layer (the “fixed” or “pinned” layer or stack) has its magnetization fixed by being exchange-coupled with an adjacent antiferromagnetic layer. The pinned ferromagnetic layer and the adjacent antiferromagnetic layer form an exchange-coupled structure.
Another type of magnetoresistive device that may be used to establish a read head is a current-perpendicular-to-the-plane (CPP) spin valve GMR sensor. The CPP spin valve read head is structurally similar to the widely used CIP spin valve read head, with the primary difference being that the sense current is directed perpendicularly through the interfaces between the two ferromagnetic layers and the nonmagnetic spacer layer.
In either case, within the scope of the present invention, it is understood that it is desirable to increase the amount of giant magnetoresistance (GMR) in spin valves, particularly those that use Ir—Mn or Ir—Mn—Cr as the pinning layer, without deleterious side effects such as degraded magnetic pinning or decreased magnetic softness of the free layer. With these recognitions in mind, the invention herein is provided.
The invention may be applied to bottom single and dual current in plane and current perpendicular to plane GMR sensors and bottom single and dual TMR sensors.
A magnetoresistive sensor structure has a magnetically pinned stack and a pinning layer including Ir—Mn (preferably, Ir—Mn—Cr) that serves to magnetically pin the pinned stack. A seed stack that includes a thin layer of Pt—Mn is provided.
In one non-limiting implementation the seed stack includes a Ni—Fe—Cr layer covered by a Ni—Fe layer, and in this embodiment the layer of Pt—Mn covers the Ni—Fe layer. In another non-limiting implementation the layer of Pt—Mn is covered by a Ni—Fe—Cr layer that in turn is covered by a Ni—Fe layer. The layer of Pt—Mn can be between one and ten Angstroms thick and preferably is five Angstroms thick, which is significantly thinner than its critical thickness of about 90 Angstroms, above which Pt—Mn can be transformed upon annealing from FCC paramagnetic phase to L10 ordered antiferromagnetic phase and can itself act as a pinning layer.
In another aspect, a method for making a magnetoresistive sensor structure includes forming a seed stack including at least one layer of Pt—Mn, and depositing onto the seed stack an antiferromagnetic layer that includes Ir—Mn—Cr. The antiferromagnetic layer may be deposited onto a sufficiently preheated seed stack to promote relatively large grain size and/or ordering of Ir—Mn—Cr from disordered antiferromagnetic FCC phase to ordered antiferromagnetic L12 phase, which enhances pinning.
In still another aspect, a magnetic recording sensor includes a free stack, a pinned stack, and a barrier between the free stack and pinned stack. An Ir—Mn—Cr layer provides magnetic pinning for the pinned stack, and a seed stack underlies the Ir—Mn—Cr layer. The seed stack includes means for promoting grain growth and interfacial smoothness in the Ir—Mn—Cr layer.
In another aspect, a magnetic storage device includes a spindle rotating a magnetic recording disk and a slider juxtaposed with the disk. The slider has at least one magnetic head and is supported by a suspension coupled to an actuator arm, the arm in turn being rotatably positioned by an actuator. The head includes a magnetically pinned stack, a pinning layer including Ir—Mn and magnetically pinning the pinned stack, and a seed stack comprising a layer of Pt—Mn.
In another aspect, a magnetoresistive sensor includes a free stack, a pinned stack, and a barrier between the free stack and pinned stack. An Ir—Mn—Cr layer provides magnetic pinning for the pinned stack, and a seed stack underlies the Ir—Mn—Cr layer. The seed stack includes means for promoting grain growth and interfacial smoothness in the Ir—Mn—Cr layer.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:
Referring initially to
Now referring to
In the embodiment shown in
In accordance with present principles, in the preferred embodiment of
Referring briefly to the alternate embodiment of
Following the seed layer 64 deposition, the sequence of layers in the spin valve structure includes an Ir—Mn—Cr antiferromagnetic pinning layer 74 of, e.g., seventy five Angstroms thickness, a pinned stack structure 76 that may be, for example but without limitation, CoFex/Ru/CoFey or CoFex/Ru/Co—Fe—B, and a layer 78 that may be, for example but without limitation, a Cu or CuOx spacer layer in CIP GMR applications, or for example but without limitation a Cu—AlOx spacer layer for CPP GMR applications. In TMR applications, AlOx may alternatively be used as a barrier layer 78, as can a wide range of other materials including, for example, MgOx or TiOx.
A free stack structure 80 that may be, for example but without limitation, Co—Fe/Ni—Fe or Co—Fe—B is deposited on the layer 78. The free stack structure 80 may be covered by a protective capping layer of, e.g., Ta or Ru that may in turn may be topped by a gap in case of CIP GMR applications, or an upper magnetic shield in the case of CPP GMR and TMR applications, in accordance with principles known in the art.
Formation of the structures shown in
With the above structure and using the preferred five Angstrom thickness of Pt—Mn, the present invention provides for non-degraded GMR, where percent GMR (i.e., the resistance change between the states when the free layer and pinned layer magnetizations are aligned anti-parallel and when they are aligned parallel divided by the structure sheet resistance) is as illustrated in
Most importantly, inserting one to ten Angstroms of Pt—Mn layer 72 between Ni—Fe layer 70 and Ir—Mn—Cr layer 74 improves the pinning fields, as measured by H50, as is shown in
The benefits shown in the above graphs may be attributable to significantly increased Ir—Mn—Cr in-plane grain size, by about forty percent, as determined by X-ray diffraction, and yet with an increased rather than decreased interfacial smoothness, as might be expected when the Ir—Mn—Cr grain size increases. This significantly larger grain size structure is also expected to substantially improve thermal stability of the GMR and TMR spin valve heads due to reduction of grain boundary diffusion.
In other embodiments, the structures shown in
While the particular SPIN VALVE WITH Ir—Mn—Cr PINNING LAYER AND SEED LAYER INCLUDING Pt—Mn as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. It is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. Absent express definitions herein, claim terms are to be given all ordinary and accustomed meanings that are not irreconcilable with the present specification and file history.
