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We investigated the switching of perpendicular exchange bias (PEB) from a negative to a positive value in an exchange-coupled Cr2O3/Pt/Co heterostructure. With varying the Pt spacer layer thickness or the measurement temperature, two types of intermediate states were found during the switching process: a double hysteresis loop indicating a local PEB and a single hysteresis loop indicating an averaged PEB. We propose a way to control the lateral ferromagnetic domain, which is associated with the type of the intermediate state, through the control of the exchange coupling magnitude.

Chromium(III) oxide is a classical collinear antiferromagnet with a linear magnetoelectric effect. We are presenting the measurements of the magnetoelectric susceptibility $\alpha$ of a sputter-deposited 500-nm film and a bulk single-crystal of Cr$_\mathrm{2}$O$_\mathrm{3}$. We investigated the magnetic phase-transition and the critical exponent $\beta$ of the sublattice magnetization near N\'eel temperature. For the films, an exponent of 0.49(1) was found below 293 K, and changed to 1.06(4) near the N\'eel temperature of 298 K. For the single-crystal, the exponent was constant at 0.324(4). We investigated the reversal probability of antiferromagnetic domains during magnetoelectric field cooling. For the sputtered films, reversal probability was zero above 298 K and stabilized only below 293 K. We attribute this behavior to formation of grains during film growth, which gives different intergrain and intragrain exchange-coupling energies. For the single-crystal, reversal probability was stabilized immediately at the N\'eel temperature of 307.6 K.

In this study, we investigated the effect of buffer layers on the blocking temperature (TB) of perpendicular exchange bias of thin Cr2O3/Co exchange coupled films with a Ru spacer and revealed a high TB of 260 K for 20-nm-thick Cr2O3 thin films. By comparing the TB values of the 20-nm-thick Cr2O3 films on Pt and α-Fe2O3 buffers, we investigated the lattice strain effect on the TB. We show that higher TB values can be obtained using an α-Fe2O3 buffer, which is likely because of the lattice strain-induced increase in Cr2O3 magnetocrystalline anisotropy.

The electric control of surface magnetism is important for spintronic applications. Due to the screening of electric field by conduction electrons in metals, an electric field can be applied only at a surface layer. However, the electric field can be applied on metallic contacts smaller than the electron's mean free path. We report on the electric modulation of the phase-transition temperature of CoO that is present at Co/Pt nano-contacts through a thin AlO x barrier. We found a 50-K/V change that can be attributed to the injection of electrons through nano-contacts.

We investigated the microwave oscillations induced by spin transfer torque with a current-perpendicular-to-plane (CPP) nanocontacts spin-valve (NCSV) structure under dc current. First, we carefully studied the influence of the stress current, at which a synthetic-antiferromagnet (SAF)-spin-flop might take place with Joule heating under the applied field for measurement, on the SAF magnetization state for CPP-NCSV with high magnetoresistance (MR) ratio of approximately 20% to determine the applied current densities of the devices for microwave oscillation measurement, and then its microwave oscillation characteristics were clarified. The clear decrease in the MR ratio due to Joule heating was observed only in NCSV devices with high MR ratios. Therefore, the critical current density of the device for the microwave oscillation decreases with an increase in the MR ratio, which improves the oscillation efficiency. It suggests that the current is more effectively confined at NCs compared with the low MR devices. As a result, we succeeded in observing excellent oscillation characteristics, i.e., a large oscillation power of 64 nW and a narrow line width of 6.5 MHz at approximately 1.1 GHz in an NCSV device.

This paper reports the film and head performance of specular spin valves with nano-oxide layer (NOL-SPSV). A large MR ratio of 17% was obtained by using an ultrathin CoFe free layer with a high conductance Cu layer, which decreases the sense current field of a free layer and brings good soft magnetic characteristics. Prototype heads with a read track width of 0.47–0.61 μm were fabricated by using NOL-SPSV films with an MR ratio of 14–15%, H ua ∼400 Oe, and H c ∼5 Oe. High output signal voltage of 8–11 mV/μm was realized in the NOL-SPSV heads.

The concept of spin-filter spin-valve (SFSV) films is reviewed. The dependence of the free layer structure on the spin-filter effect was investigated by using model films and two types of free layers were compared, a single CoFe layer and a conventional NiFe/Co free layer. At the same magnetic thickness of the free layer, the SFSV films with a CoFe free layer showed a larger magnetoresistance (MR) ratio than those with a NiFe/Co free layer. This is partly attributed to the thinner CoFe free layer thickness, which is due to the fact that the CoFe free layer has higher Bs than the NiFe/Co free layer. Moreover, SFSV films with a CoFe free layer still showed a larger MR ratio when the free layer thickness was the same. It suggests that other factors contribute to the high MR performance, such as the quality of the interface between a free layer and a high conductance layer. Film performance of MR 9% to 10%, ΔRs 1.5–2.0 Ω, Hcea∼3 Oe, and λs⩽±0.5 ppm was obtained with a single CoFe free layer and synthetic anti...

We investigated the tunneling electroresistance (TER) in metal/wurtzite-MgZnO/metal junctions for applications in nonvolatile random-access memories. A resistive switching was detected utilizing an electric-field cooling at ±1 V and exhibited a TER ratio of 360%–490% at 2 K. The extracted change in the average barrier height between the two resistance states gave an estimation of the MgZnO electric polarization at 2.5 μC/cm2 for the low-temperature limit. In addition, the temperature-dependent TER ratio and the shift of the localized states energies at the barrier interface supported the ferroelectric behavior of the MgZnO tunnel-barrier. From the first-principles calculations, we found a similar effect of the barrier height change coming from the reversal of ZnO electric polarization. The possibility of using metal electrodes and lower growth temperatures, in addition to the ferroelectric property, make the ZnO-based memory devices suitable for CMOS integration.

Neutron-diffraction measurements were made on an ordered Mn3Ir single crystal in a wide temperature range up to 1030 K. The ordered Mn3Ir alloy was found to maintain an antiferromagnetic (AF) triangular spin structure up to the Neel temperature TN=960±10 K. The lattice parameter a shows a continuous change in the temperature range including TN. In contrast to the isostructural ordered Mn3Pt alloy, these observations indicate that an AF–AF phase transition is absent in the ordered Mn3Ir alloy.

The insertion of a nano-oxide-layer (NOL) into a spin valve system is well known to be very effective in enhancing the magnetoresistance ratio at both of current-in-plane (CIP) and current-perpendicular-to-plane (CPP) geometries. Recently, a clear NOL pinning assist effect is reported to be observed in the low temperature range below ~150 K by using the magnetic field cooling method from room temperature (R.T.) in the Co0.9Fe0.1 pin-NOL, wherein the NaCl-type CoO-FeO antiferromagnetic component exists. In this paper, the NOL pinning assist effect in a specular spin valve system with (Co-Fe)/Cr pin-NOL is presented. An ultra-thin Cr layer deposit on the Co-Fe layer before oxidation leads to increase the exchange bias field still more with the increment of the blocking temperature (TB)of the (Co-Fe)-NOL biasing in the low temperature range below R.T. and to fully exploit the superior pinning properties of the metallic antiferromagnet (Ir-Mn) at R.T. in the Co-rich region. The effect of ultra-thin Cr layer on the NOL exchange bias is considered from the aspect of the complicated oxide formation and its magnetism.

When the surface energy of bottom layer is lower than top layer, the atoms of bottom layer should be pumped up at the triple point of the grain boundary. This phenomenon should be useful for the fabrication of well-defined nanobridge. To confirm the Atom Pumping-Up mechanism for metal/metal thin films, Ta(2 nm) on epitaxial MgO(001)/Fe(001) films were prepared by the electron beam deposition method. The Pumping-Up mechanism was successfully confirmed by the Auger Electron Spectroscopy, the in situ Scanning Tunneling Microscopy, and the Transmission Electron Microscope observation after heat treatment of 400 degCtimes30 min. The size of the Fe bridges was 2-5 nm. Furthermore, the magnetic exchange coupling effect on the magnetization process through the ferromagnetic bridges between two Fe layers in MgO/Fe/Ta/Fe after Atom Pumping-Up shows a good agreement to the micromagnetics simulation result from the assumption of ferromagnetic bridges with the size of 1-4 nm

We have achieved a magnetoresistance (MR) ratio of 7%-10% at a resistance area product (RA) of 0.5-1.5 Omegamum2 by ferromagnetic FeCo nanocontacts in Al nano-oxide-layer (NOL) with current-perpendicular-to-plane spin-valve (CPP-SV) structure. Conductive atomic-force-microscopy shows clear current-path regions of a few nanometers in size surrounded by the Al-NOL. The MR dependence on resistance area product (RA) is well explained by the current-confined-path model assuming that the spin-dependent scattering has an FeCo nanocontact origin, different from tunnel magnetoresistance (TMR). Resistance increases with increasing bias voltage, indicating joule heating by high-current density in nanocontacts, in contrast to TMR. The MR origin is mainly interpreted as spin-dependent scattering due to domain wall formed at ferromagnetic nanocontact

The B2 structure Fe50Co50 alloy is very attractive material as a large spin conductance asymmetry. In this study, we have tried to fabricate epitaxial Fe/Co superlattice with B2 structure. In order to investigate the relationship between the film structure and the substrate temperature, the films were prepared at different substrate temperature. The film structure of Fe/Co was evaluated by reflection high energy electron diffraction (RHEED). The in-plane lattice spacing gradually decreased to that of a bulk Fe50Co50 as increase in the number of layers. The B2 structure ordered phase of Fe/Co superlattice was successfully confirmed by RHEED and X-ray diffraction (XRD).

The exchange bias properties of the Co/sub 1-x/Fe/sub x/ natural-oxidized nano-oxide layer (NOL) in the specular spin valve system are investigated. The exchange bias energy (J/sub ex/) increased with the Fe content of the CoFe NOL. This result suggests that the enhancement of the pinning field/energy at room temperature was induced by the inserted NOL into the pinned layer. The enhancement of both the magnetoresistance ratio and the exchange bias field was realized by increasing the Fe content in the Co/sub 1-x/Fe/sub x/ NOL.

We have succeeded in designing, fabricating, and testing GMR/inductive heads. 1 /spl mu/m trackwidth CoFe spin-valve read elements showed high sensitivity even after head fabrication due to its good thermal stability. About 1.5 /spl mu/m trackwidth a-CoZrNb write elements with Bs (Saturation flux density) of 1.35 T fabricated by trench filling process showed high potential for Gbit density recording. As a result of the feasibility study, 18 kTPI and 140 kBPI are thought to be within the scope by combining the dual element heads with low-noise media.

We have compared the magnetoresistance (MR) performance of current-confined-path (CCP) current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) spin valve films with a nano-oxide-layer (NOL), made between natural oxidation (NO) and ion-assisted oxidation (IAO). For the NO, an MR ratio was only 1.5% at an RA of 370 m/spl Omega//spl mu/m/sup 2/, whereas for the IAO, an MR ratio was greatly increased to 5.4% at an RA of 500 m/spl Omega//spl mu/m/sup 2/. Fitted data by the Valet-Fert model showing larger MR enhancement effect by the IAO is explained by the improvement of the metal-purity of the Cu inside the CCP structure. By further improvement of metal-purity of the Cu, a large MR ratio of more than 30% can be expected at a small RA of 300 m/spl Omega//spl mu/m/sup 2/. The CCP-CPP spin valve film is a promising candidate for realizing high-density recording heads for 200 to 400-Gbpsi recording.

We investigated the magnetic properties of the Co/sub 1-x/Fe/sub x/-natural oxidized nano-oxide layer (NOL) in the specular spin-valve system by precise measurement of magnetization at 77 K and M-T curves after field cooling at /spl plusmn/5 kOe. The result suggests the antiferromagnetic component behavior of the NOL and its Ne/spl acute/el temperature (T/sub N/) shifts to the higher temperature with increasing Fe composition. Below the T/sub N/, the antiparallel spin configuration at the pinned layers is stabilized by the exchange bias field induced from antiferromagnetic component of NOL by the field cooling in negative field direction.

The anisotropic magnetostrictions of the cubic Laves phase compounds Gd(Fe1−xCox)2 and Dy(Fe1−xCox)2 pseudobinary system have been measured from 8 to 130 K below their ordering temperatures. The concentration dependence of anisotropic magnetostriction for these two systems has been observed. An attempt is made to find the reason for the high magnetostriction in DyCo2 and GdCo2. The results obtained suggest that the high anisotropic magnetostriction of RCo2 (R:Gd, Dy) relates to the strong magnetocrystalline anisotropy caused by cobalt.

The Morin transition of a (0001)-oriented iridium-doped α-Fe2O3 thin film deposited on an Al2O3(0001) substrate was studied by 57Fe-grazing incidence synchrotron radiation Mossbauer spectroscopy (GISRMS). Temperature-dependent spectra proved that the iridium doping markedly enhanced the Morin temperature of the α-Fe2O3 thin film; the iron spin directions were perpendicular to the film plane at temperatures below 100 °C, while they were in-plane at temperatures above 150 °C. The antiferromagnetic ordering was maintained far above 400 °C. The results demonstrated the availabilities of 57Fe-GISRMS, which enables a very quick evaluation of the magnetism in antiferromagnetic ultrathin films at high temperatures.

We have reported that body-centered-cubic (bcc) Fe50Co50 with ultrathin Cu layers has large spin-dependent bulk scattering and enhances AΔR of spin valves. In order to clarify the role of Cu, two series of samples with (Fe50Co50 1 nm/Cu)×5 were prepared by two different sputtering machines. Machine A has a high rate, and machine B has a comparatively low rate. Both of AΔR in series A and B are increased by inserting thin Cu of about 0.1 nm, but they have a significant difference in Cu thickness dependence. While series A keeps high AΔR through the Cu thickness, AΔR in series B decreases when Cu is thickened. In order to find the reason for the difference, we took the extended x-ray absorption structure (EXAFS) spectra. By comparing AΔR and EXAFS, it was found that the very thin Cu of about 0.1 nm in Fe50Co50 takes a body-centered-cubic bcc structure, namely a solid solution state. Cu of 1 nm in spin valves with high AΔR takes a bcc and face-centered-cubic (fcc) evenly, and that with a low AΔR is a fcc str...

Micro magnetic device simulation studies are reviewed. Flux density distributions and loss analyses are summarized, and the authors' method of analysis using a transmission line model is described. These results are a very significant step toward the establishment of an optimal device design. It is expected that CAD techniques will be established in future.

The authors propose a novel structured magnetic thin film inductor using rotation magnetization only. The thin film inductor has a sandwich structure, which consists of a double-rectangular spiral coil between top and bottom CoZrNb amorphous thin films. The sputtered CoZrNb amorphous magnetic thin films have uniaxial magnetic anisotropy induced by direct current field annealing. The easy magnetization axis is directed to the main axis of the rectangular spiral coil. Hence, only the rotation magnetization process dominates in this device. The typical specifications are as follows; 3.5/spl times/5.5 mm in size, inductance of 1 /spl mu/H constant up to 10 MHz, and a quality factor of 10 at 10 MHz. A MHz switching chopper dc-dc converter has been developed by using this thin film inductor, bare-chip semiconductor devices (a power MOSFET and a Schottky barrier diode), and a multilayer ceramic capacitor. This converter with a 0.1 cc volume has an output power over 1 W at 5 MHz switching, and the power density exceeds 10 W/cc (160 W/in/sup 3/). >

Co90Fe10/Cu spin-valve structures were prepared by the RF and DC magnetron sputtering methods. X-ray diffraction data showed that the spin-valves on a sapphire substrate exhibited good fcc (111) preferred orientations. The maximum value of Δρ/ρ0 was 11%, which was larger than that obtained for Co/Cu spin-valve structures.

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.

Three different techniques, natural oxidation, remote plasma oxidation and low energy ion beam oxidation, have been proved to be equally effective in forming nano-oxide layers (NOLs) in spin-valve films for specular enhancement of giant magnetoresistance (GMR) effect. GMR values over 12% have been routinely obtained in spin-valve films with NOL, corresponding to a 30% specular enhancement over those without NOL. The consistency and robustness of the oxidation processes has been demonstrated by a very large GMR value ∼19% in a dual spin-valve film with the NOLs formed in both pinned layers, the oscillatory dependence of the interlayer coupling field on Cu layer thickness in specular enhanced spin-valve films and the uniform and repeatable film performance over 5 in. substrates.

RFe 10 Si 2 (RLa, Pr, Nd, Sm, Gd, Er and Zr compounds were synthesized by the rapid quench method. The ThMn 12 structure can be obtained in the RFe 10 Si 2 system containing RSm, Gd and Er, while the NaZn 13 structure can be obtained in the system containing RLa, Pr and Nd. It has also been found that Nd 1− x Zr x Fe 10 Si 2 ( x = 0.25, 0.5 and 0.75) crystallized in the ThMn 12 structure. The factors which control the formation of ThMn 12 and NaZn 13 structures in the RFe 10 Si 2 system are discussed with respect to the atomic radius of the rare earth site element.

In order to research the high magnetostriction effect of some rare-earth transition metal intermetallic compounds such as the RFe2 or RCo2, systems, we have investigated microscopically the physical properties of Dy(Fe1−xCox)2 by Mossbauer spectroscopy. Hyperfine field(Bbf), quadrupole splitting(Q.S.) and isomer shift(I.S.) in the Dy(Fe1−xCox)2 system have been measured at room temperature and 78 K. The easy axis of magnetization lies along the [100] axis. Especially we have found the close correlation between Q.S. and magnetostriction, that is the Q.S. for Dy(Fe1−xCox)2 increase in the Co rich region where the magnetostriction become large at 78 K.

Investigations were made into the relationship between the exchange-coupling properties and the IrMn crystal grain size for CoFe/IrMn spin valves. The IrMn crystal grain size increased with increasing thickness and decreasing oxygen content of the IrMn layer. The increase in the IrMn grain size resulted in a higher blocking temperature (TB) but a lower unidirectional anisotropy field (HUA). This opposite dependence of TB and HUA on the IrMn grain size is different from those of other antiferromagnetic films such as FeMn, NiMn, and CrMnPt. An HUA of 400 Oe at room temperature and a TB of 300 °C are obtained for CoFe (2 nm)/IrMn (10 nm) spin valves by controlling the oxygen content of the IrMn layer.

Dependence of magnetic properties and microstructure on boron additions for nitrogenated (Sm,Zr)(Fe,Co)/sub 9/ alloys fabricated by rapidly quenching was investigated. The condition for getting high (BH)/sub max/ with high /sub i/H/sub c/ is to produce an amorphous phase in the rapidly quenched sample because it leads to the precipitation of uniform and fine grains by the annealing above their crystallization temperature. The role of boron is to form the amorphous phase easily by rapidly quenching. High (BH)/sub max/ of about 20 MGOe with high /sub i/H/sub c/ of 9.6 kOe was obtained for nitrogenated (Sm/sub 0.7/Zr/sub 0.3/)(Fe/sub 0.95/Co/sub 0.05/)/sub 9/B/sub 0.1/. High (BH)/sub max/ of 13.0 MGOe was also attained as an isotropic resin bonded magnet with density of 6.2 g/cm/sup 3/.

We have succeeded in designing, fabricating, and testing self-alignment trench-pole write heads. 1 /spl mu/m narrow track heads were fabricated by a newly developed self-alignment trench process and showed large overwrite of over 40 dB for low-noise high coercivity media with Hc=2800 Oe, even with a large throat height of 3 /spl mu/m. This trench pole writer showed high potential for submicrometer narrow track application.

An epitaxial wurtzite (WZ) Mg0.23Zn0.77O barrier based magnetic tunnel junction (MTJ), with electrode-barrier structure of Co0.30Pt0.70 (111)/Mg0.23Zn0.77O (0001)/Co (0001), was fabricated. The good crystallinity and tunneling properties were experimentally confirmed. Electrical and magnetic investigations demonstrated its high resistance-area product of 1.05 MΩ μm2, a maximum tunneling magneto-resistance (TMR) of 35.5%, and the existence of localized states within the tunneling barrier producing TMR rapid decrease and oscillation when increasing the applied bias voltage. The TMR value almost vanished at 200 K, which was attributed to the induced moment and strong spin-orbit coupling in Pt atoms at the Co0.30Pt0.70/Mg0.23Zn0.77O interface. Owing to the ferroelectric behavior in WZ-MgZnO materials, the fabrication of WZ-MgZnO barrier based MTJs deposited on a metallic ferromagnetic electrode will open routes for electrically controllable non-volatile devices that are compatible with CMOS technology.

We experimentally investigated the asymmetric transmission probabilities of spin-up and spin-down electrons at a (001)-Fe/Ag interface, which result in a highly spin-dependent interface resistance () that improves the magnetoresistive outputs of giant magnetoresistive devices whose ferromagnetic layers comprise only 3d transitional materials such as FeCo-based alloys. We quantitatively determined the spin-dependent interfacial parameters at FexCo100-x/Ag interfaces that were tuned by varying the Fe concentration x. Among the interfaces, the highest interface resistance of 0.65 mΩµm2 was obtained with an of 1.89 mΩµm2, which corresponds to ARF/N↑ ~ 1.08 mΩµm2 and ARF/N↓ ~ 7.98 mΩµm2 at a (001)-Fe/Ag interface.

The structural properties and Morin transition in c-plane-oriented α-Fe2O3 and Ir-doped α-Fe2O3 thin films have been investigated. The enhancement of the Morin transition temperature (TM) in α-Fe2O3 film by Ir doping has been demonstrated. The TM in the c-plane-oriented α-Fe2O3 thin film was determined from the temperature-dependent in-plane magnetization and change of coercivity (Hc); this TM value was found close to that of bulk α-Fe2O3. The spin directions of non-doped and Ir-doped α-Fe2O3 at room temperature were also estimated from conversion electron Mossbauer spectroscopy measurements. We confirmed that Ir doping dramatically enhances the TM of α-Fe2O3 thin film.

The (001)-oriented and (110)-oriented epitaxial grown Co2Fe0.4Mn0.6Si films were fabricated by magnetron sputtering technique in order to investigate the annealing temperature dependence of the intrinsic Gilbert damping constant ( α). The stuck films, deposited on MgO and Al2O3 a-plane substrates, respectively, were annealed at various temperatures ranging from 400 °C to 550 °C. The X-ray diffraction analysis was conducted to confirm that all the films were epitaxially grown. In addition, the ferromagnetic resonance measurements as well as the vibrating sample magnetometer were carried out to determine their magnetic properties. A small α of 0.004 was recorded for the sample with 001-oriented Co2Fe0.4Mn0.6Si (CFMS (001)) and 110-oriented CFMS (CFMS (110)) annealed at 450 °C.

The lattice parameter dependence of the Neel temperature TN of thin Cr2O3 in a Cr2O3/Co exchange-coupled system is investigated. Lattice-mismatch-induced strain is generated in Cr2O3 by using different buffer layers. The lattice parameters are determined from out-of-plane and in-plane X-ray diffraction measurements. The Neel temperature is detected by direct temperature-dependent magnetization measurement as well as the temperature-dependent interface exchange coupling energy. It is observed that in-plane lattice contraction can enhance TN in Cr2O3, which is consistent with theoretical calculations.

We investigated the magnetoelectric properties of Cr2O3/Co all-thin-film exchange coupling system with Cr spacer layer. In this system, significantly small coercivity (Hc

Annealing time and temperature dependences of MR ratio in CoFe/Cu spin-valves were investigated. Thermal deterioration of MR ratio was well explained by considering two phenomena with effective activation energies of 2.16 eV and 1.57 eV for CoZrNb/NiFelCoFe/Cu/CoFe/FeMn spin-valves, and considering one phenomenon with a value of 2.49 eV for CoZrNb/NiFe/CoFe/Cu/CoFe/IrMn spin-valves, respectively. These values are in good agreement with activation energies of interdiffusion based on the vacancy mechanism. It is shown that no significant change in MR ratio is evaluated from the effective activation energies for the period of more than 10 years at 150/spl deg/C in CoZrNb/NiFe/CoFe/Cu/CoFe/IrMn spin-valve films.

In this study, we introduce the energy application such as annealing on the Al as deposition state and from molecular dynamics (MD) simulations, the details of atomic configurations for Al atoms on Cu(l 11) surface were investigated. Using this method we can control the size of the Al grains, and, hence, the CCP phenomena can be controlled and improved.The current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect has been greatly attracted for its application to ultra high density storage devices.

The authors discuss and investigate the characteristics structural, magnetic and current-perpendicular-to-the-plane giant magnetoresistance (CPPGMR) properties of Fe/Co superlattices on an Au electrode. RHEED images showed the surface reconstruction during deposition and indicated that Fe/Co 59 multilayers (MLs) on Au electrode has B2 ordered structure at 400degC substrate temperature.

We investigated the effect of Pt insertion on a Cr2O3/Co exchange coupling system. The perpendicular exchange bias μ0Hex decreased with increasing Pt insertion layer thickness, and we observed positive μ0Hex for samples with relatively thick Pt insertion layers. We also examined the cooling field μ0Hfc dependence of μ0Hex for the samples. At small μ0Hfc, all samples exhibited negative μ0Hex. With increasing μ0Hfc, a shift of μ0Hex from negative to positive was observed. In the past, similar behaviors were observed for FeF2/Fe systems exhibiting positive μ0Hex. In addition, the μ0Hfc dependence of μ0Hex was well fitted by an equation taking into account the Zeeman energy at the surface of an antiferromagnet as well as an antiferromagnetic exchange coupling. The results strongly suggest that (1) Cr2O3 surface spin is affected by the external magnetic field and (2) the coupling at the Cr2O3/Pt/Co interface is antiferromagnetic.

We succeeded in developing CoFe spin valves with an antiferromagnetic Ir-Mn film. Ir-Mn single-layer films and spin valves of Ta(5 nm)/Ir-Mn(8 or 9 nm)/Co90Fe10(x nm)/Cu(3 nm)/Co90Fe10(3 nm)/NiFe(2 nm)/CoZrNb(10 nm)/ (x=2, 2.3, 2.6 nm), prepared by the sputtering method, showed the crystal structure of a fcc (111) preferred orientation. As-deposited CoFe spin valves with Ir-Mn exhibited an interfacial exchange coupling energy of J=0.192 erg/cm2 (Hua∼640 Oe at tCoFe=2 nm), that was the highest ever reported for as-deposited antiferromagnetic films, such as NiO, NiMn, and FeMn. Furthermore, CoFe spin valves with Ir-Mn exhibited a higher blocking temperature of 260 °C, and a higher MR ratio of 6.37% than the spin valves with FeMn film. After annealing, the MR ratio increased to 7.82%. On the other hand, the Hua decreased about 100 Oe after annealing. The Hua-T curve was, however, improved and the Hua at 100 °C increased to 400 Oe. The decrease in Hua was not observed after second annealing and seems to be st...

The thermal reliability of spin valve films with a CoZrNb/NiFe/CoFe free layer and a CoFe/IrMn pinned layer was investigated. Stable properties; including an MR ratio of 7.5/spl sim/8%, an exchange bias of 400/spl sim/500 Oe in the pinned layer, an interlayer coupling of less than 10 Oe between the pinned and free layers, and soft magnetic properties of the free layer, were observed even after annealing for 100 hours at 270/spl deg/C. It was demonstrated that the IrMn/CoFe interface, as well as the CoFe/Cu interface, is extremely stable against interdiffusion. These films also showed an MR ratio of 5% and an exchange bias of 200 Oe even at 160/spl deg/C.

This paper investigates in-situ characterization method for metallic path shapes and their distributions inside the nano-oxide layer (NOL) by using the conductive atomic force microscopy (AFM) and reports on the effect of the assist energy upon the formation of the metallic path inside Al-Cu NOL. Film stacks of Cu/Al are deposited on a thermally oxidized Si substrate by ECR ion beam sputtering. RHEED images reveal that further increasing the annealing temperature to more than 200/spl deg/C, the disappearance of the clear rings from the Cu or the Al surfaces can be recognized due to the structural change by the alloying or segregation in both Al/Cu and Cu/Al bi-layer samples. Topographic images of the sample unoxidized with bias voltage of 0.5 V show round shape microstructures and there are both bright and dark areas in the electric current (conductive AFM) image where a bright one means apparently the shape of the metallic channels on the surface of the NOL. On the other hand, topographic images of samples annealed at 300/spl deg/C before oxidation show a decrease in grain size and channel size.

To confirm the origin of the exchange field from nano-oxide layer (NOL), the detailed analyses of the magnetization curve and the temperature dependence on magnetization for the Co/sub 1-x/Fe/sub x/-NOL inserted samples were investigated. The room temperature NOL exchange biasing superimposed on AFM exchange bias in specular spin-valve (SPSV) is also considered to realize CIPGMR (current in plane giant magnetoresistance) with higher sensitivity and a more stable pinned layer for high density magnetic recording head.