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The transport properties of hybrid free, synthetic, and specular spin valve (SV) at film level are reviewed and their potential for read head application are discussed. Synthetic pinned SV and specular SV have good thermal stability because of either high effective exchange field or good protection from interdiffusion with MOLs.

High tunneling magnetoresistance (TMR) ratio and low RA in magnetic tunnel junctions are necessary condition for application in magnetic random access memory. To get high TMR ratio and low RA, good quality of MgO (002) insulating layer is important. To increase crystalline quality of MgO (002) layer, we applied negative bias on the substrate during MgO deposition. We report the results of the tunneling magnetoresistance (TMR) ratio and the resistance-area product (RA) for CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with substrate bias voltage, and showed TMR increase and RA decrease with substrate bias. The effects of substrate bias voltage on the TMR ratio, RA and MgO (002) peak intensity are discussed. Index Terms--Magnetic tunnel junctions (MTJs), resistance-area product (RA), substrate bias, tunneling magnetoresistance (TMR).

We report on the magneto-transport measurements of MgO magnetic tunnel junctions (MTJs) composed of NiFeSiB/CoFeB as the free layer for two different structures (top-type and bottom-type pinning). The magneto-transport properties of these MTJs were investigated by varying the thickness of the amorphous NiFeSiB layer for a fixed CoFeB thickness. The tunnel magnetoresistance (TMR), measured in both type of structures, exhibit the same or a higher amplitude (up to 230% measured at room temperature in the case of top-type device), comparing to the case of a single CoFeB free layer. These results suggest that hybrids free layers can be used as good candidates for MTJs with reduced saturation magnetization while keeping a high TMR ratio. Index Terms--Amorphous, hybrid free layer, magnetic tunnel junction, NiFeSiB.

Professor Albert Fert and Peter Grunberg are to be awarded the Nobel Prize in Physics for the year 2007 because of their research in giant magnetoresistance that increased the storage capacity of disk drives.

A four-state magnetic random access memory (MRAM) was developed using an epitaxial [Co.sub.50][Fe.sub.50]-MgO-[Co.sub.50][Fe.sub.50] magnetic tunnel junction (MTJ) with a tunnel magnetoresistance (TMR) ratio of 145% at room temperature (RT). Four remanent magnetization states in the single-crystalline [Co.sub.50][Fe.sub.50] electrode, due to the cubic anisotropy with easy axes of the /110) directions, result in four possible angular-dependent TMRs, each separated by more than 20% at RT. Analysis of the asteroid curve for [Co.sub.50][Fe.sub.50] indicated that the magnetic field along 22.5[degrees] from the directions made it possible to change the magnetization direction of the selected cell without disturbing those of the half-selected cells. Index Terms--CoFe, magnetic tunnel junction (MTJ), magnetoresistance (MR), multistate magnetic random access memory (MRAM).

A fully sealable matrix-based magnetoresistive biochip has been recently introduced for the detection of biomoleeular recognition events. This work reports results for a 3 x 3 cells matrix comprising hydrogenated amorphous silicon diodes (PIN and Schottky) and aluminum oxide magnetic tunnel junctions (MTJ). The noise characteristics of the individual thin film diodes (TFD) and the MTJ were analyzed for measuring frequencies from DC to 1 kHz, allowing the detection of single magnetic nanopartieles with 250 nm and 130 nm diameters. For 50 nm particles, and at 1 kHz, minimum number of detectable labels ranges from 20 (Schottky diodes) to 50 (PIN diodes). Index Terms--DNA-chips, magnetic nanoparticles, magnetic tunnel junction, magnetoresistive biochips.

This paper describes the improvement on the defect detection performance of printed circuit board (PCB) inspection based on the eddy-current testing (ECT) technique with the multispin-valve giant magnetoresistance (SV-GMR) sensor. To obtain the ECT signal in the same scanning line, SV-GMR sensors are mounted on the exciting coil in the same column parallel with the scanning direction. Harmonic analysis based on the Fourier transform is used to analyze the signal from the SV-GMR sensor in order to increase scanning speed. Then signal averaging is applied to the ECT signal in order to improve the signal-to-noise ratio. Experimental results are per- formed to verify the inspection performance. Index Terms--Eddy-current testing (ECT), muitisensor, printed circuit board (PCB), scanning speed, signal averaging, signal-to-noise ratio (SNR), spin-valve giant magnetoresistance (SV-GMR).

In this paper, we present a spin torque included dynamic micromagnetic modeling investigation on the perpendicular magnetoresistive random access memory design. A small inject current always generates a steady magnetization precession of the eomposite storage layer around perpendicular axis. For a given current density, the precession frequency is lower when the Gilbert damping constant of the perpendicular layer is higher. It is found that magnetization reversal of the perpendicular storage layer occurs when the lateral precession frequency reaches the ferromagnetic resonance condition. To reach the required precession frequency, a higher current density is required for a great value of damping constant of the perpendicular layer. Index Terms--Damping constant, ferromagnetic resonance, magnetoresistive random access memory (MRAM), perpendicular MRAM, spin torque.

To demonstrate the highest areal recording density of tape media, we have developed a metal evaporated tape with higher magnetic anisotropy of 2.5 x [10.sup.5] J/[m.sup.3] and finer magnetic activation volume of 2.7 x [10.sup.-24][m.sup.3] of a Co-CoO recordin la er de osited on a g yp smoother base film. A capability of an areal recording density of 23.0 Gb/[in.sup.2] was confirmed using a giant magnetoresistive head as a read head. The smoother surface roughness improved signal-to-noise ratio more than 2 dB. Index Terms--Areal recording density, giant magnetoresistive head, magnetic tape recording, metal evaporated.

The band structure calculations, structures, transport and magnetic properties in two dimensional layer structured perovskite compounds [Sr.sub.2-x][La.sub.x]Co[O.sub.4] are presented. The results have shown that the system is metallic with a high spin polarization that is responsible for the large magnetoresistance.

The effects of ion irradiation on a giant magnetoimpedance (GMI) are examined for a Co-based amorphous ribbon with different ions like Xe, Ar and N. The analysis has shown that the ion irradiations have modified the magnetic properties including a large coercivity and shearing of the in-plane magnetization loops, thus indicating the reduction of an exchange coupling.

The steplike impedance change for thin-film giant magnetoimpedance (GMI) element is analyzed. The analysis has shown that the magnetic energy of the two phases have intersected each other in a certain external magnetic field, indicating that the basis of steplike GMI of thin-film element is disclosed as a structural change of magnetic domain based on magnetic energy.

Microstructured magnetic tunnel junction ring with outer/inner diameter of 2/1 [micro]m has been fabricated to investigate the angular dependence of magnetoresistance during magnetization reversal process. The minor loop of magnetoresistive curve reveals four distinct resistance levels associated with four magnetization configurations within the free layer throughout the magnetization reversal. The magnetoresistance decreases with increasing angle between applied external field and biasing direction, which is resulted from the relative alignment of total magnetization of pinned and free layer. An extra feature appeared in the minor loop when the external field is transverse to the biasing direction; this can be attributed to a vortex-pair formation/annihilation in the free layer. Furthermore, a series of schemes of magnetic configurations of pinned and free layers are illustrated to explain the routes of minor loops. Index Terms--Magnetization reversal, magnetoresistance, magnetoresistive devices.

We report the results of current-induced magnetization switching (CIMS) for MgO-based magnetic tunnel junctions (MTJs) with a tunneling magnetoresistance (TMR) ratio of about 66% and a critical current density of 4.45 x [10.sup.6] A/[cm.sup.2]. The stable switching probability related to CIMS over 1 x [10.sup.4] cycles is observed up to 90%. The influence between the switching current and the pulse duration is discussed. Index Terms--Current-induced magnetization switching (CIMS), magnetic tunnel junction (MTJ), switching probability, tunneling magnetoresistance (TMR).

A double-barrier-layer perpendicular magnetic tunneling junction (DpMTJ) structure consisting of Si substrate/Pt/GdFeCo/AlOx/GdFeCo/ FeCo/AlOx/FeCo/TbFeCo/Pt/Ti-cap was prepared by a direct current (dc) and radio frequency (RF) magnetron sputtering method. An elliptical DpMTJ element with 3.5 [micro]m x 2.5 [micro]m size was fabricated using a top-down technique. A conducting atomic force microscope (CAFM) was used to obtain I-V curves of DpMTJ structures. We obtained the magnetoresistance (MR) ratio value from measured I-V curves by applying two opposite magnetic fields value of [+ or -] 200 Oe perpendicular to the plane of film. The MR ratio was reached as high as 74% at zero applied bias voltage. Furthermore, the MR ratio decreased as bias voltage increased. It could make the DpMTJ structure to be used in the high-density MRAM devices. Index Terms--Magnetic tunneling junction (MTJ), magnetoresistance (MR).

We have systematically investigated the complex impedance (CI) and complex capacitance (CC) spectra of MgO-based magnetic tunnel junctions (MTJs) due to successive annealing. The variation of the tunnel magnetoresistance (TMR) ratio due to annealing can be related to the change of interfacial trap states and textured MgO based on the analysis of CI spectra by an equivalent circuit model. The results of CC spectra are also consistent with the analysis of CI and observed TMR ratio variation. The CI and CC techniques are also powerful to characterize the oxide-based MTJs. Index Terms--Complex capacitance (CC), complex impedence (CI), MgO, equivalent circuit model (ECM), tunnel magnetoresistance (TMR).

Giant magnetoresistance (GMR) type Co-Cu multilayers and exchange-biased spin-valve (EBSV) type Co-Cu-Co tri-layers are fabricated by sputtering with a thin layer of Ag inserted between Co and Cu as a surface modifier (SM). Their magnetoresistances (MR) are measured in both current-perpendicular-to-plane (CPP) and current-in-plane (CIP) configurations. In all situations, the size of the MR change decreases as the Ag SM is introduced, and the effect is interface related. Index Terms--Current-in-plane (CIP), current-perpendicular-to-plane (CPP), exchange-biased spin-valve (EBSV), giant magnetoresistance (GMR), surface modifier.

Temperature dependence of thermally activated ferromagnetic resonance (FMR) has been studied for two kinds of tunneling magnetoresistive (TMR) heads with a track width of about 100 nm. It is found that the power spectral density (PSD) is composed of a FMR peak and a resonance kink at slightly lower frequency. For the TMR head with a well-defined magnetization state (single domain) of the free layer, the kink is much smaller than the peak in amplitude, and the FMR peak increases in its amplitude and shifts to lower frequency as temperature increases. However, for the TMR head with a hysteretic magnetization behavior, the FMR peak is blurred by the kink and no discernible shift of its position can be detected as temperature increases. It is observed that the noise power can be redistributed among different resonance modes at different temperatures and fields. Index Terms--Magnetic noise, power spectral density, tunneling magnetoresistive heads.

Microstructured magnetic tunnel junction rings have been fabricated by a top-down technique combining electron beam lithography and ion milling process. Four-terminal magnetoresistance measurements and magnetic force microscopy were used to successfully explore a four-transition process within the free layer throughout the magnetization reversal. Various magnetization configurations were identified to be the onion state, vortex-pair state, vortex state, vortex-core state, and reverse onion state. In addition, the various durations of each magnetic state observed in the magnetoresistance curve can be utilized for the study of a coupling effect between the pinned layer and the free layer. Index Terms--Fabrication, magnetic force microscopy (MFM), magnetization reversal, magnetoresistance.

We have investigated the mechanism of weak exchange bias for a spin valve with threshold layer antiferromagnetic (AFM) thickness using giant magnetoresistance (GMR) and polarized neutron reflectometry (PNR). Results show that the sample exhibits instantaneous switching of the free layer followed by a gradual reorientation of the magnetization in the pinned ferromagnetic layer via domain wall formation. During subsequent field cycles, we found that relaxation in the pinned ferromagnetic (FM) layer is induced not only by an increasing field, but also in a static field over a relatively long time scale. Index Terms--Antiferromagnetic (AFM) materials, giant magnetoresistance (GMR), interface magnetism.

Synthesis and characterization of transition metal (TM)-doped [In.sub.2][O.sub.3] oxide is reported. Most of the samples were found to be paramagnetic, and only Fe and Cr co-doped sample showed as light trace of ferromagnetism at 300 K with saturation magnetization [M.sub.s] = 0.35 emug/g. Measured transport properties revealed significant differences in transport among the samples. The absolute value of electrical resistivity for the [In.sub.1.8][Fe.sub.0.1] [Mn.sub.0.1][O.sub.3] sample at 300 K was [rho] : 9.4 x [10.sup.3] [OMEGA] * cm, while [In.sub.1.8][Fe.sub.0.1][Cr.sub.0.1][O.sub.3] had [rho] : 62 [OMEGA] * cm at the same temperature. Furthermore, magnetoresistance (MR) studies of [In.sub.1.8][Fe.sub.0.1][Cr.sub.0.1] [O.sub.3] showed that the sign of MR changes from negative (200 K), with [MR.sub.(200K)] = -0.2%, to positive T < 50 K reaching maximum absolute value at 10 K, i.e., [MR.sub.(10K)] = 5.2%. Index Terms--Diluted semiconductors, magnetoresistance (MR) effect, spintronics.

GaAs and GaN pn-junctions are fabricated with Mn-doped ferromagnetic layers on top of nonmagnetic substrates. In the ease of heavily doped (Ga,Mn)As/GaAs [p.sup.++][n.sup.++]-junctions (Zener diodes) the tunneling current becomes magnetic field dependent at low temperatures. This can be explained by a model based on the valence band splitting due to the exchange interaction between the hole spins and the localized spins of the Mn atoms. In the pn-junctions with more lightly doped nonmagnetic regions in the (Ga, Mn)N and (Ga, Mn)As diodes, no magnetic field dependence in the I-V characteristics is observed, probably due the absence of ferromagnetism in the depletion region of the [p.sup.+] n-junctions. Index Terms--Magnetic semiconductors, magnetoresistance, spin-dependent tunneling.

Graphene-a single atomic layer of graphite--is a recently found two-dimensional (2-D) form of carbon, which exhibits high crystal quality and ballistic electron transport at room temperature. Soft magnetic NiFe electrodes have been used to inject polarized spins into graphene, and a 10% change in resistance has been observed as the electrodes switch from the parallel to the antiparallel state. This coupled with the fact that a field-effect electrode can modulate the conductivity of these graphene films makes them exciting potential candidates for spin electronic devices. Index Terms--Magnetoresistive devices, soft magnetic films, thin films.

In this study, current-perpendicular-to-plane great magnetoresistance (CPP-GMR) spin valves with the minimum pillar width of 34 nm [phi] were successfully fabricated using EB-assisted chemical-vapor-deposition (CVD) hard masks. An area of the obtained magnetic cell is about one order smaller compared with those fabricated with normal EB or photo lithography technique. Measurement of transport properties such as current-induced magnetization switching (CIMS) and MR were demonstrated in such spin valves with various pillar widths. Dependence of the CPP-MR properties on the milled pillar width was discussed. In the case of 66 nm [phi] width in particular, the MR by external magnetic field switching and CIMS were 0.4% and 0.3%, respectively. The critical switching current [I.sub.c] was ~40 mA ([J.sub.c] ~ 9 x [10.sup.8] A/[cm.sup.2]). In the case of smaller width, only MR by external magnetic field was observed. Index Terms--Chemical-vapor-deposition (CVD), CPP-GMR spin valve, critical current density, current-induced magnetization switching (CIMS), electron beam (EB), magnetoresistance (MR), scanning electron microscope (SEM).

We present a detailed investigation into the intrinsic tunnel barrier reliability in AlOx-based magnetic tunnel junctions (MTJs) as a function of aluminum thickness and oxidation time. The intrinsic reliability is measured as the ramped breakdown voltage ([V.sub.bd]) at room temperature for both positive and negative polarity. We find that [V.sub.bd] generally increases with the resistance-area (RA) product of the MTJ. While this dependence is quite strong at low RA, it gradually weakens for higher RA. At fixed RA, [V.sub.bd] also depends on the original Al film thickness with better properties for thicker Al. Finally, we observe a polarity dependence of [V.sub.bd] which changes sign as the MTJ goes from thin Al to thick Al. We attribute the polarity dependence to the different quality of the top and bottom interfaces and conclude that the interface emitting the tunneling electrons primarily governs the barrier reliability. Index Terms--Dielectric breakdown, magnetic memories, magnetoresistive devices, reliability, tunneling.

Magnetic tunnel junctions (MTJs) with partially oxidized 9-[Angstrom] [AlO.sub.x]-barriers were recently shown to have the necessary characteristics to be used as magnetoresistive sensors in high-density storage devices. Here we study dielectric breakdown in such underoxidized MTJs, focusing on its dependence on tunnel junction area and oxidation time. A clear relation between breakdown mechanism and junction area is observed for the MTJs with the highest studied oxidation time: samples with large areas fail usually due to extrinsic causes (characterized by a smooth resistance decrease at dielectric breakdown). Small area junctions fail mainly through an intrinsic mechanism (sharp resistance decrease at breakdown). However, this dependence changes for lower oxidation times, with extrinsic breakdown becoming dominant. In fact, in the extremely underoxidized magnetic tunnel junctions, failure is exclusively related with extrinsic causes, independently of MTJ area. These results are related with the presence of defects in the barrier (weak spots that lead to intrinsic breakdown) and of metallic unoxidized Al nanoconstrictions (leading to extrinsic breakdown). Index Terms--Dielectric breakdown, magnetic tunnel junctions (MTJs), magnetoresistance (MR).

Highly spin-polarized tunneling with tunnel magnetoresistance (TMR) ratios of 90% at room temperature and 240% at 4.2 K was demonstrated for fully epitaxial magnetic tunnel junctions fabricated using a cobalt-based full-Heusler alloy [Co.sub.2][Cr.sub.0.6][Fe.sub.0.4]Al (CCFA) thin film having a composition close to the stoichiometric one and a MgO tunnel barrier. A high tunneling spin polarization of 0.79 at 4.2 K was obtained for the epitaxial CCFA films from the TMR ratios. This adds to the promise of the fully epitaxial MTJ as a key device structure for utilizing the intrinsically high spin polarizations of Co-based full-Heusler alloy thin films. Index Terms--Co-based full Heusler alloy, half-metallic ferromagnet, magnetic tunnel junction, tunnel magnetoresistance.

Electron transport property in the nanocontacting wire was investigated by measuring magnetoresistance effect. In the regime of conductance quantization, the magnetoresistance exhibits the quantized step (in the unit of [e.sup.2]/h) and nonquantized step ([DELTA]G < [e.sup.2]/h). The magnetoresistance effect appears to be large in the case that either of the steps was observed in a magnetoresistance curve, indicating that there are different mechanisms which bring about the giant magnetoresistance. Index Terms--Ballistic magnetoresistance (BMR), conductance quantization, nanocontact.

A nano fabricated planar point contact (PC) in NiFe film showed a magnetoresistance (MR) ratio of about 18%, and it stabilized at about 12%; with both values being much larger than those for the anisotropic MR (AMR) ratio of the film. The measurements of current-driven resistance change in the PC were also performed in which about 10.5% resistance change was observed. The saturated resistances coincided with the typical values in the MR measurements (MR: 12%). These results inspired correlation between MR and domain wall. Index Terms--Magnetic confinement, magnetic domains, magnetoresistance, nanotechnology.

A new method for correlating the far infrared magnetorefractive effect (MRE) and giant magnetoresistance (GMR) is tested on commercially grown CoFe/Cu multilayers. Parameters are determined to demonstrate a simple relationship between prominent features of an MRE spectrum and the size of the electrical magnetoresistance. The results encourage the use of the new approach for sensing GMR in thin films. Index Terms--Conductivity, giant magnetoresistance, infrared spectroscopy, magnetic films, magnetooptic effects.

In this paper, we propose an alternative method to improve magnetoresistance by inserting a thin ferromagnetic (FM) layer into the nonmagnetic (NM) spacer of a basic spin-valve (SV) trilayer (FM1-NM-FM1), thus creating a penta-layer SV structure (FM1-NMFM2-NM-FM1). We investigated the effect of increasing the resistivity ([[rho].sub.F2]) of the FM2 on overall magnetoresistance (MR). We performed both analytical and numerical studies on the MR of the current perpendicular-to-plane (CPP) structure using the phenomenological spin drift-diffusion models. For finite [[rho].sub.F2], the MR profile is dependent on the intrinsic conductance polarization ([[alpha].sub.F2]) of FM2. We found that inserting FM2 enhances MR when [[alpha].sub.F2] exceeds a critical value of [[alpha].sub.2C]. It is found that MR can be doubled by inserting a FM layer with high [[alpha].sub.F2], such as the half-metallic [Cr.sub.2]O. We have numerically calculated [MR.sub.max]. and the corresponding [[rho].sub.F20] values for different [[alpha].sub.F2] values. Finally, we studied the effect of spin relaxation on the MR of the CPP SV. Index Terms--Current perpendicular-to-plane (CPP)-GMR, ferromagnetic, magnetoresistance (MR), spin valve (SV).

We investigated current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) with current screen layer of various Co-Fe compositions. The resistance-area product (RA) and the change in the resistance-area product ([DELTA]RA) increased with increasing Fe compositions in the current screen layer up to 25 at.%. However, they were very low at Fe compositions above 50 at.%. It seemed that the boundaries of the RA and [DELTA] RA dependences on Co-Fe composition were similar to that of the Co-Fe composition between fcc and bcc structures. Based on transmission electron microscopic observations, the current screen layer composed of [Co.sub.90][Fe.sub.10] was formed uniformly, and it had an epitaxially crystalline structure. On the other hand, the current screen layer composed of [Co.sub.90][Fe.sub.10] was formed with a large degree of roughness, and it had a complicated crystalline structure. This suggests that a uniform current screen layer with an epitaxially crystalline structure is important to enhance the MR ratio for CPP-GMR. Index Terms--Co-Fe composition, CPP-GMR, current screen layer, spin-valves.

A spin-valve sensor biochip was used to detect cystic fibrosis related DNA targets for the purpose of developing an affordable diagnostic chip. The strategy used was based on the ac field focusing of magnetically labeled target DNA at sensor sites using U-shaped current lines. U-shaped spin-valve sensors, fabricated within the line structures, detected in real-time the hybridization of DNA targets to complementary DNA probes, previously immobilized onto the chip surface. Hybridization occurred in relatively short times (15-30 min) in comparison with conventional hybridization approaches (3 to 12 h). Statistical data on detection signals for single probe and multiprobe experiments was obtained, showing a significant difference between complementary binding signals and noncomplementary and background ones. Index Terms--Biomedical transducers, DNA, magnetic particles, magnetoresistive devices, medical diagnosis.

Microstructured permalloy ellipses have been fabricated using electron-beam lithography through a lift-off process. The investigations were focused on the magnetization configurations and switching processes adopting magnetic force microscopy (MFM) and magnetoresistance (MR) measurements. An original five-vortex domain configuration of ellipse can be controlled and manipulated to become a four-vortex domain configuration by tuning the external magnetic field applied along the short-axis direction. In addition, an asymmetrical reversal process can be demonstrated on an ellipse having two- or three-vortex domain configuration, in which the switching fields are 36 Oe and 24 Oe, respectively. Index Terms--Magnetic force microscopy (MFM), magnetization switching, magnetoresistance, permalloy.

We have investigated the low temperature resistance and magnetoresistance behavior of ferromagnetic cobalt wires in perpendicular external magnetic fields of up to B = 5 T. Magnetic force microscopy investigations show that the cobalt wires are single-domain at remanence, if the wire width is smaller than about 800 nm. At low temperatures a logarithmic resistance increase is observed which is consistently explained as originating from enhanced electron-electron interaction (EEI) in two dimensions, while the magnetoresistance is dominated by the anisotropic magnetoresistance. Additional resistance corrections due to weak electron localization (WEL) are not observed within the accuracy of our measurements, which is discussed in the framework of recent experimental and theoretical works. Index Terms--Electron-electron interaction, location, magnetoresistance.

In this paper, we demonstrate that tunnel magnetoresistive (TMR) elements can be used as sensitive on-chip current sensors in the microampere to milliampere range for current-based IC testing such as power-pin testing and quiescent [I.sub.dd] current (IDDQ) testing. The sensor can be integrated in CMOS ICs containing magnetic random access memory. TMR current sensors with various lateral dimensions (from submicrometer to micrometer) arranged in a Wheatstone bridge have been realized and analyzed. A typical sensitivity of 2.5 (mV/V)/mA and a current resolution of 5.5 [micro]A have been observed. The influence of the sensor geometry on sensor sensitivity, hysteresis, and temperature rise due to Joule heating has been investigated. Index Terms--Current sensor, integrated circuit (IC) testing, magnetic random access memory (MRAM), tunnel magnetoresistance (TMR).

We describe a large magnetoresistance (MR) effect in organic light-emitting diodes that reaches up to 10% at fields of 10 mT at room temperature. This MR effect occurs both in [pi]-conjugated polymers and small molecules. Our devices do not contain any magnetic materials. We found that the MR effect is only weakly temperature dependent and does not depend on sign and direction of the applied magnetic field. This is a novel type of MR--yet to be explained theoretically--that does not have, to the best of our knowledge, an analog in inorganic semiconductor devices. Index Terms--Magnetoresistance, magnetoresistive devices, organic compounds, plastics.

A linear giant magnetoresistive (GMR) isolator was modeled and the output voltage and current in relation to the input current were investigated. The feedback coil current (output current) corresponding to the input coil current closely matched the reported experimental results when the gain of the op-amp modeled was high (500). In the triangular input current wave response, feedback coil current faithfully followed the input current when the slew rate of the input coil current was equal to or lower than that of the op-amp and the input coil current amplitude was within the linear region of the isolator response. Index Terms--GMR, isolator modeling, linear isolator.

The bias-dependent complex impedance spectra of ion-beam sputtered CoFe-Al[O.sub.x]-CoFe tunnel junctions have been systematically investigated. An equivalent circuit model, composed of a resistance component and two sets of parallel resistance (R) and capacitance (C) components in series, has been utilized to describe the individual impedance contribution from lead of cross patterns, CoFe-Al[O.sub.x] interfaces and bulk Al[O.sub.x] in CoFe-Al[O.sub.x]-CoFe tunnel junctions. The fitting results reveal that the RC component characterizing the CoFe-Al[O.sub.x] interface can be explained by a Schottky barrier with imperfectly blocking characteristic, which is attributed to the existence of traps in the depletion region. The tendency of interfacial resistance, [R.sub.i], and interracial capacitance, [C.sub.i], as a function of dc bias, [V.sub.dc], is expected for the space charge limited current model with exponential trap distribution, which coincides with the analyzing results of dc four-probe current-voltage curves. On the other hand, the R and C components of bulk Al[O.sub.x] almost remain constant when [V.sub.dc] increases, in contrast to the electrical behavior of CoFe-Al[O.sub.x] interfaces. The results suggest the metal-insulator interface, instead of bulk insulator, dominates the electrical transport process of MTJs. Index Terms--Bias-dependent impedence, magnetic tunnel junctions, tunnel magnetoresistance.

Giant magnetoresistive (GMR) multilayers with high GMR sensitivity might find application in low-end magnetic sensors. Electrode-position of FeCoNi/Cu GMR multilayers directly onto n-type silicon was carried out from a single electrolyte and their magnetotransport properties were investigated. Inhomogeneous dissolution of the ferromagnetic (FM) layer during Cu sublayer deposition has an important role in determining the shape of the GMR characteristics; lower dissolution promotes sharper interfaces and larger slopes of the GMR versus field curve at low fields. An increase of the Fe content in the FM sublayers reduces coercivity but promotes selective dissolution and degrades interface sharpness. Electrodeposition conditions are optimized to achieve a maximum GMR of 9% saturated at < 0.5 kOe, and a maximum GMR sensitivity of over 0.11%/Oe in the field range 5-15 Oe with a saturation GMR of 6.1%. Index Terms--Electrodeposition, FeCoNi/Cu, magnetic multilayers, magnetoresistive sensitivity.

This paper describes the detection of conductive microbeads (PbSn) based on eddy-current testing (ECT) technique. High-frequency magnetic field applied to the conductive microbeads enables spin-valve giant magnetoresis-tance (SV-GMR) sensor to detect the magnetic fields occurred from eddy currents flowing in the conductive microbeads. In this paper, analysis of these magnetic fields by an analytical method is discussed and compared with experimental results. Index Terms--Conductive microbead, eddy-current testing, high-frequency, spin-valve giant magnetoresistance.

We report on X-ray magnetic circular dichroism experiments performed on [Co.sub.5] [Cu.sub.95] as-quenched and annealed granular alloys with giant magnetoresistance (GMR). Results of the Co-[L.sub.2,3] edges give evidence of a direct correlation between the Co orbital and spin magnetic moment with the Co clusters interfacial roughness, a matter that is critical in the GMR response. Index Terms--Giant magnetoresistance, granular alloys, X-ray magnetic circular dichroism.

Nanogranular films of composition [Ag.sub.100-x][Fe.sub.x] (x: 10, 14, 20, 26, 30 at %) were prepared by dc plasma sputtering deposition. All films exhibit a negative magnetoresistance whose intensity decreases monotonically with temperature, with no apparent saturation up to 50 kOe. A magnetic correlation range [R.sub.m] is obtained from analysis of the GMR versus M/[M.sub.S] curves. The role of interparticle correlation is investigated as a function of both Fe concentration and temperature. Index Terms--Correlations, magnetoresistance, thin films.

The (Cr-M)[O.sub.2] (M = V, Mn, Fe, Co) powders were synthesized by the mechanochemical method and the magnetoresistance (MR) effect of their powder compacts was investigated as a function of the type and content of the dopant. The findings are summarized as follows. 1) Substituting limit of M for Cr in Cr[O.sub.2] was 30 at% for V, Mn, and Co, and 5 at% for Fe. 2) Doping with V effectively decreases the [T.sub.C], while Fe significantly elevates the same (420 K with 5 at% Fe). Furthermore, the changes observed in the cases of Co and Mn was marginal. 3) MR ratio was significantly enhanced with the doping of 5 at% of Fe, however, decreased in the cases of V and Co doping. 4) The reason for the MR enhancement in (Cr-Fe)[O.sub.2] powder compacts is due to the change in the barrier characteristics. Index Terms--Chromium dioxide, half metal, intergranular tunneling, magnetoresistance, tunnel barrier.

New metal particle (MP) media was developed for use with giant magnetoresistive (GMR) heads. We confirmed the capability of constructing a helical scan magnetic recording system exceeding 3 Gb/[in.sup.2] recording density, because of sufficient signal-to-noise ratio (SNR) under test conditions at 6.74 Gb/[in.sup.2] of read-track-base calculations with the media (magnetic layer thickness : 50 nm, magnetic particle size = 45 nm, and surface roughness Ra : 1.8 nm). Low media partial-abrasive properties are incorporated to avoid excessive head gap material wear. Index Terms--Areal recording density, metal particle (MP) tape, spin-valve head, partial abrasive.

The read response of a giant magnetoresistive (GMRI sensor was calculated using a micromagnetic model taking into account the full interaction between a GMR sensor and a double-layered medium. The simulated results showed that the magnetic interaction between the sensor and the recording medium scarcely influenced the signal waveforms and the roll-off properties. The comparison of the isolated waveform and the roll-off with those obtained from the modified Fan's equation suggested that there is a nonlinearity in the read process of a GMR sensor. Index Terms--Giant magnetoresistive (GMR) head, micromagnetic model, perpendicular magnetic recording, roll-off properties, soft under layer.

Testing degradation and predicting tile lifetimes of giant magneto-resistive (GMR) heads under mechanically and thermally accelerated conditions are discussed. Our experiments revealed that accumulated mechanical acceleration can cause gradual and continuous head degradation. The amplitude loss was proportional to the integrated acoustic emission (AE) signal, and the amplitude loss rate to the integrated AE was a function of GMR temperature. Lifetime predictions with these parameters are presented. Index Terms--Acoustic emissions (AEs), degradation, giant magneto-resistive (GMR) heads, lifetime predictions.

The read performance, especially peak asymmetry, of current-perpendicular-to-the-plane giant-magnetoresistive (CPP-GMR) heads with a current screen layer (nano oxide layer having a confined current path) was investigated through a spin stand test and a micromagnetic simulation. We fabricated CPP-GMR heads having a magnetoresistive (MR) ratio of 3%. The head-amplifier signal-to-noise ratio of the CPP-GMR heads with longitudinal media was 18-27 dB with a bandwidth of 200 MHz. The peak asymmetry of these heads has a complicated dependence on the sensing current. This complicated behavior can be explained in terms of the particular transfer curve for the CPP-GMR head. The transfer curve calculated from the micromagnetic simulation was 'stair-like,' having kinks caused by the current-induced field. Increasing the sensing current changes the positions of the kinks on the transfer curve. This stair-like transfer curve directly influences the peak asymmetry through the sensing current. Accordingly, the longitudinal bias field, sensor size, and current-induced biasing should be considered when controlling the peak asymmetry of the CPP-GMR heads. Index Terms--CPP-GMR, current induced field, nano oxide layer, peak asymmetry, read performance, SNR.

In order to study the magnetic behaviors of pinned layers under different conditions, we applied compressive mechanical stress to a device and measured the transfer curve changes using a high-field (10 kOe) quasi-static tester. This permitted us to determine the behaviors of the pinned layers and the free layer. The results of the transfer curve measurements led to a classification of these curves. The governing conditions for each category were also determined. A normal transfer curve occurs when '[E.sub.j] > Eu [much greater than] [E.sub.k](AP1) and [E.sub.k](AP2),' where: AP1 is the pinned layer adjacent to the antiferromagnetic (AFM) layer; AP2 is the pinned layer adjacent to the spacer; [E.sub.u], is the coupling energy constant between the antiferromagnetic layer and the AP1 ; [E.sub.j] is the anti-parallel coupling energy constant between AP1 and AP2 through the Ru; and [E.sub.k](AP1) and [E.sub.k](AP2) are the induced uniaxial anisotropic energy constants in API and AP2 due to magnetostriction resulting from stress applied giant magnetoresistive (GMR) sensor. Index Terms--Anisotropic energy, antiferromagnet, giant magnetoresistive (GMR), high-field transfer curve, pinned layers, quasi-static tester.

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. Index Terms--Exchange coupling, giant magnetoresistance (GMR), nano-oxide layer (NOL), specular reflection, spin valves.