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In this paper, we report the performance of bottom synthetic spin-valve films with a newly developed ruthenium (Ru)-based nano-oxide layer (NOL). Two energetic oxidation techniques using an ion beam and a gas cluster ion beam were applied for the formation of the Ru NOL in the synthetic pinned layer. The giant magnetoresistance (GMR) was greatly enhanced from 13.8% to 15.7% with no sign of degradation in the pinning strength. In addition, these Ru NOL-bearing spin-valve films have demonstrated an excellent thermal stability, withstanding repeated thermal annealing cycles at elevated temperatures. This performance is clearly superior to that from the spin-valve films with a conventional CoFe-based NOL. The Ru NOL has shown a great potential for high-amplitude read sensor applications. Index Terms--Bottom synthetic spin valve, gas cluster ion beam (GCIB), giant magnetoresistance (GMR), ion beam oxidation (IBO), nano-oxide layer (NOL), oxidation, pinned layer, pinning field, ruthenium (Ru), thermal stability.

Thin films of magnetic and nonmagnetic constituents of spin-valve and magnetic tunnel junction multilayers were deposited using magnetron sputtering techniques as a function of argon pressure. Depositions in the sub-milli-Torr pressure regime have greatly improved film surface smoothness but also induced significant changes in film stress and, therefore, magnetostriction. The comparable values of magnetic thickness loss generated at various magnetic/nonmagnetic interfaces by the sub-milli-Torr deposition suggests comparable energetic deposition to ion beam deposition. A proper selection of deposition conditions for the component layers is critical to ensure optimal performance of spin-valve and magnetic tunnel junction multilayers. Index Terms--Interlayer atomic mixing, magnetic thickness loss, magnetostriction, magnetron sputtering, stress, sub-milli-Torr, thin films.

Ultrathin Al[O.sub.x] layers 5-25 [Angstrom] thick were deposited using the atomic-layer chemical vapor deposition technique. A magnetic thickness loss of ~1 [Angstrom] has been estimated at CoFe-A1[O.sub.x] or NiFe-A1ONiFe-Al[O.sub.x] interfaces. The two-dimensional integrity of the thin Al[O.sub.x] films at thickness >7 [Angstrom] has been validated by the differential switching of two magnetic layers sandwiching a ultrathin Al[O.sub.x] layer and the distinct cross-sectional transmission-electron-microscopy images. No appreciable tunnel magnetoresistance effect has been measured from the fabricated magnetic tunnel junction devices. A proper in situ treatment prior to and/or after Al[O.sub.x] deposition and a proper protection of the underlying magnetic layer are expected for further improvements. Index Terms--Atomic-layer chemical vapor deposition (ALCVD), A1[O.sub.x], decoupling, J-V, magnetic thickness loss, magnetic tunnel junction (MTJ), thin films, tunnel magnetoresistance, tunnel barrier.

In this paper, we present results of a study on [Ni.sub.81][Fe.sub.19]/Cu MLs deposited using a four-source DC magnetron sputtering system operated in planetary mode. A significant change of GMR value with deposition conditions, especially base pressure and deposition pressure, has been observed for [Nis.sub.81][Fe.sub.19]/Cu MLs. With an optimized process, we have obtained a GMR response of 9.5% with a field sensitivity of 0.44%/Oe for Si/[[([Ni.sub.81][Fe.sub.19])17[Angstrom]/Cu20[Angstrom]].sub.20] MLs without an Fe buffer layer. The insertion of a very thin layer of a second magnetic species at nonmagnetic/magnetic interfaces in the ML stack makes GMR response either sensitive or less sensitive to deposition conditions depending on the species selected. We believe that the key to obtaining large GMR values in [Ni.sub.81][Fe.sub.19]/Cu MLs lies in the control of layered structure and interfacial chemistry. In addition, these [Ni.sub.81][Fe.sub.19]/Cu MLs survive high temperature annealing up to 250 C, retaining a GMR value of 8.5%. The thermal stability exhibited by these MLs over the temperature range for device fabrication makes them valuable for high density recording head sensor applications.

We present the results of a systematic study on optimization of the giant magnetoresistance (GMR) response in Co/Cu multilayers (MLs) for Cu layer thickness near the second oscillatory peak. Co/Cu MLs with alternating thick ([[t.sup.(1)].sub.Co]) and thin ([[t.sup.(2)].sub.Co]) Co layers have been prepared in the form of [[[[Cot.sup.(1)].sub.Co][Angstrom]/Cu20[Angstrom]/[Cot.sup.(2)].s ub.Co][Angstrom]/Cu20[An gstrom]].sub.15]. We have found that the magnetoresistive hysteresis of these MLs is reduced with decreasing [[t.sup.(2)].sub.Co] and has disappeared when [[t.sup.(2)].sub.Co] < 4.5 [Angstrom]. We have obtained an optimal GMR response with a field sensitivity of 0.13%/Oe over a field region of [approximately]60 Oe centered at [approximately]50 Oe. This architecture may enable the use of Cu/Co MLs in low-field magnetic sensor applications.

We have fabricated and tested GMR magnetic sensors that operate in the CPP mode. This work is a continuation of the ultra-high density magnetic sensor research introduced at INTERMAG 96. We have made two significant modifications to the process sequence. First, contact to the sensor is made through a metal conduit deposited in situ with the multilayers. This deposition replaces electroplating. This configuration ensures a good electrical interface between the top of multilayer stack and the top contact, and a continuous, conductive current path to the sensor. The consequences of this modification are an increase in yield of operational devices to [greater than or equal to]90% per wafer and a significant reduction of the device resistance to [less than or equal to]560 m[ohms] and of the uniformity of the device resistance to [less than or equal to]3%. Second, the as-deposited multilayer structure has been changed from [[Cu 30 [Angstrom]/Co 20 [Angstrom]].sub.18] (third peak) to [[Cu 20.5 [Angstrom]/Co 12 [Angstrom]].sub.30] (second peak) to increase the GMR response. The best second peak CPP GMR response from a single device is 39%. The sensitivity of that device is 0.13 %/Oe.

Nano-Oxide Layers (NOL) have been introduced recently as a means to enhance the degree of specular scattering at the outer surfaces in a spin-valve, while still using metallic antiferromagnets such as PtMn or IrMn. A key requirement of the NOL layer in the pinned layer is to be able to provide strong ferromagnetic coupling between two ferromagnetic layers. In this paper, a quantitative study of the ferromagnetic interlayer coupling over the NOL-layer is presented. A Stoner-Wohlfarth model is developed to allow for quantitative analysis. The effect of different metal deposition methods (PVD or IBD), different pinning structures (PtMn and IrMn; simple and synthetic) and different oxidation methods on the coupling is compared. Index Terms--Magnetoresistance, specular reflection, spin-valve.

A large giant magnetoresistance (GMR) value of 7.5% has been measured in simple NiFeCo(1)/Cu/NiFeCo(2) sandwich films grown on a 30 [Angstrom] Cr seed layer. This spin-valve GMR effect is consistent with the differential switching of the two NiFeCo layers due to an enhanced coercivity of the NiFeCo(1) layer grown on the Cr seed layer. A change in growth texture of the NiFeCo(1) layer from fcc (111) to bcc (110) crystallographic orientation leads to an increase in magnetic anisotropy and an enhancement in coercivity. The GMR value increases to 8.7% when a thin CoFe interfacial enhancing layer is incorporated. Further enhancement in GMR values up to 14% is seen in the sandwich films by nano-oxide layer formation. The specular reflection at the oxide/magnetic layer interface further extends the mean free path of spin-polarized electrons. Index Terms--GMR, sandwich, spin-valve, seed layer, coercivity, nano-oxide layer, specular reflection.

We investigated the effect of aluminum thickness on RA (resistance [multiplied by] area product) and MR ratio in spin-dependent tunnel junctions. Very low RA values below 40 [Omega]/[[micro]m.sup.2] and a maximum MR ratio of 6% were obtained in [Ni.sub.81][Fe.sub.19]/[Al.sub.2][O.sub.3]/[Ni.sub.81][Fe.sub.19] tunneling junctions fabricated using natural oxidation of aluminum. The MR ratio significantly increased with use of [Co.sub.90][Fe.sub.10] electrodes. Using natural oxidation of 6 [Angstrom] aluminum, RA and MR ratio of these junctions are ~50 [Omega][[micro]m.sup.2] and ~28%, respectively. The MR ratio and the junction resistance strongly depend on the aluminum thickness. The optimum thickness of aluminum is 6-7 [Angstrom] for natural oxidation. Index Terms--Giant magnetoresistance, magnetic films and devices, magnetic materials for heads, magnetic spin tunneling.

IrMn exchange biased bottom spin-valve films of structure Ta/underlayer/ IrMn/CoFe/Cu/CoFe/NiFe/Ta were prepared using ion beam deposition techniques. The exchange bias field exhibits strong underlayer thickness dependence. For the first time, a large exchange energy of 0.29 erg/[cm.sup.2] was measured in spin-valve films exchange biased by a disordered antiferromagnet, comparable to the values usually obtained in spin-valve films exchange biased by an ordered antiferromagnet. We have conducted a comparative study on both bottom and top exchange biased spin-valve and ferromagnetic/antiferromagnetic bilayer films. The results indicate that the exchange field obeys very well the inverse pinned layer thickness law over a thickness range from 200 [Angstrom] down to 10 [Angstrom]. The exchange energy for bottom spin-valve films is, however, a factor of two larger than that for top spin-valve films. When normalized, the exchange field exhibits the same temperature dependence for both bottom and top spin-valve films. The enhancement in exchange biasing is mainly attributed to an enhanced texture for fcc (111) crystallographic orientation of the IrMn layer in bottom spin-valve films. Index terms-exchange bias, ion beam deposition, bottom spin-valve, underlayer, IrMn

We have designed and fabricated dual spin valve heads with synthetically pinned layers. They have excellent sensitivity. The read-back waveform has a small asymmetry and that is also insensitive to the bias current. The read gap length is of 0.14 [micro] m and the write gap length is of 0.2 [micro] m. The read heads have a nominal magnetic trackwidth of 0.5 [micro] m and a nominal write magnetic trackwidth of 0.8 [micro] m. The write heads were conventional inductive heads with their pole geometry defined by focused ion beam (FIB) technology. The dual spin valve heads have achieved an areal read/write density as high as 14.5 Gb/[in.sub.2] at a data transfer rate of 23~24 MB/sec. The sensitivity of the readers is as high as 3.6 mVp-p/[micro] m. The bit aspect ratio is as high as 14. Index Terms--Dual spin valve head, GMR reader design concept, GMR head thermal stability, synthetic antiferromagnetic-pinned layers.

We have observed a 30% of enhancement in coercivity, [H.sub.c], or a 40% increase in remnant magnetization in ion beam deposited (IBD) Cr/CoPt films as compared to IBD Cr/CoCrPt films. In addition, the magnetic properties of these hard bias films exhibit a strong dependence of on substrate and underlayer. Higher coercivity values associated with enhanced hcp Co (10??0) crystallographic orientation were measured in films grown on substrates in the preference order of glass, Si/[Al.sub.2][O.sub.3] and Si. CoPt films grown on CrV underlayer show lower [H.sub.2] values than films deposited on Cr underlayer. [H.sub.c] exhibits a maximum with increasing Cr underlayer thickness for both Cr/CoPt and Cr/CoCrPt films. This Cr thickness dependence of [H.sub.2] is correlated well with that of Co (10??0)/(0002) x-ray diffraction peak intensity ratio, indicating the role of crystallographic texture in control of coercivity of IBD hard bias films. Index Terms--IBD, Hard bias film, Microstructure, MR recording head.

Presents the results of a study regarding the characteristics of Ni18Fe19/Cu multilayers deposited by direct current planetary magnetron sputtering techniques. Experimental details; Results of the study; Conclusions.