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The crystal chemistry and magnetic properties of polycrystalline Ba(Sub 3)MRuIrO(sub 9) (M(super 1+) = Li, Na; M(super 2+) = Mg, Ni, Zn; M(super 3+) = Bi, In) are investigated. It is found that there are antiferromagnetic interactions within the phase sharing octahedra that contain a disordered mixure of Ru and Ir on a single crystallographic site.

The crystal chemistry and magnetic properties of mixed ruthenium-iridium triple-perovskite series Ba(sub 3)MRuIrO(sub 9) (M = Y, lanthanides) is described. It is found that Ba(sub 3)Ln(super 3+)RuIrO(sub 9) compounds have less weiss constants, low effective magnetic moments at low temperatures, consistent with antiferromagnetic correlation.

IrMn/[Co/Pt]n and [Pt/Co]n/IrMn multilayers in the as-deposited state shows a perpendicular exchange bias. The study conducted focuses on the magnetic-field annealing effects and the correlation between perpendicular exchange bias and magnetic anisotropy.

It is of increasing importance to understand and measure the effect of damage caused by the contact between the head and disk in magnetic recording system since the head to disk spacing is reduced. In this paper, we developed a new testing method to study the influence of the mechanical stress and studied the mechanical stress robustness of PtMn and IrMnCr heads which have a synthetic ferri-coupled magnetic pinned layer structure with PtMn and IrMnCr antiferro magnetic film. Pinned layer damage types were categorized using high field transfer curves. We found that amplitude degradation is due to pinned layer damage caused by mechanical stress. Mechanical stress robustness of IrMnCr heads is superior to that of PtMn heads. Index Terms--Antiferro magnetic film, high field transfer curve, IrMnCr, mechanical stress, pinned layer, PTMN.

Structural and magnetic characterizations are performed on exchange-biased multilayers, namely, Ta/X/IrNm/Y/Ta where X and Y are Py and Co. A direct link is observed between the exchange bias variation with temperature and the magnetic disorder.

The magnetoresistance of antiparallel (AP) coupled self-pinned spin valves was measured utilizing Ir as a coupling layer. The magnetoresistance ratio increased quasilinearly from 2.2% to 4.0% with a reference layer thickness as expected from the Valet-Fert model in the long spin diffusion length limit.

A magnetoresistance study of submicrometer size elements where the anisotropic magnetoresistance (AMR) was controlled by suitably selecting the Ir content in (FeNi)Ir alloys is presented. At high fields a negative slope in the MR-H characteristic is obtained as in NiFe structures, indicating that the high field behavior evolves from a distinctly different mechanism from that of AMR.

The coupling between top and bottom pinned layers through various nano-oxide layers (NOLs) in IrMn-based spin valves is investigated. It is indicated that the biquadratic coupling between pinned Co(sub 90)Fe(sub 10) layers through NOLs results from the coupling between Fe (or Co(sub 90)Fe(sub 10)) and Fe(sub +3) oxides.

The exchange bias in polycrystalline IrMn/NiFe is found at perfectly compensated interfaces. It was seen that the coercive field of partly uncompensated ferromagnetic/antiferromagnetic bilayers increases with decreasing intergrain exchange interactions within the ferromagnet.

The magnetic domain structural, magnetic properties and thermal stability of IrMn biased top spin valves containing Co and NiFe are examined. Co-SV exhibited the maximum magnetoresistance (MR) ratio of 9.6 percent while the MR ratio of NiFe-Sv was 4.6 percent.

The low temperature properties of IrMn spin valves Ti(50 A)/NiFe(40 A)/Co(8 A)/Cu(30 A)/Co(30 A)/IrMn(t A)/Ti(50 A) are examined. Giant magnetoresistance (GMR) is adversely affected at lower temperature with thin IrMn.

The introduction of a NiFe/antiferromagnetic-MnIr bilayer or a NiFe/MnIr/NiFe trilayer below a CoTaZr soft underlayer and the effect of exchange biasing on the spike noise are discussed. The spike noise from the CoTaZr layer with a thickness below 100 nm declined with the addition of the NiFe/MnIr/NiFe trilayer by restraining the formation of domain walls.

The magneto-optical Kerr effect is used for examining the exchange bias of different types of patterned NiFe/IrMn microstructures. The patterning of exchange coupled double layers into small dimensions resulted in the decline of the exchange field.

The antiferromagnetic-ferromagnetic exchange coupling between IrMn and FeTaN films is investigated to study the effects of the exchange field on the high frequency response and the thermal stability of the anisotropy field of FeTaN. The exchange anisotropy is shown to be important in determining the high-frequency parameters of the permeability.

Thin films of IrMn were made by magnetron sputtering, using nominally 20 at. % Ir, and their structural and magnetic properties were evaluated for use as an exchange bias material. The data suggests that spin-flop models for exchange bias may not apply to IrMn, and that small spin structures dominate low temperature behavior.

The study has examined the use of the laminated antiferromagnet PtMn/IrMn to exchange bias spin valves in an attempt to combine the high exchange field and blocking temperature of PtMn with the good pinning profile of IrMn. For both top and bottom spin valves the laminated antiferromagnet showed improvement in thermal stability compared to deposited and annealed IrMn spin valves.

Magnetic hysteresis loops (MHLs) are comparatively measured on both textured and single crystalline [Sc.sub.5][Ir.sub.4][Si.sub.10] superconductors. Three kinds of peaks of the flux pinning force are observed at low fields near zero, intermediated fields, and high fields near the upper critical field.

The various effects of the substrate thickness on the static, as well as the dynamic properties of the exchange biased multilayers fabricated onto ultrathin flexible substrates. The ultrathin flexible substrates are shown to be extremely beneficial for obtaining high permeability, hence making the layers useful for microwave applications.

Several numerical simulations are conducted to analyze the properties and the magnetic failure taking place in the giant magnetoresistance spin valve read sensors. Changes in temperature and current distribution is shown to lead to different mass-transport mechanisms in the sensors.

The angular distribution of exchange bias and its size dependence are analyzed in MgO magnetic tunnel junctions with IrMn antiferromagnetic pinning layer. Device size is in the mesoscopic range where the finite number of antiferromagnetic grains has determined the statistical properties of exchange bias.

The article explains the fabrication of a new strain sensor, which is shown to be based on the stress- magnetoresistance effect of the Ni-Fe/Mn-Ir exchange-coupled magnetic film. The change taking place in the resistivity is shown to be proportional to the applied compressive stress of the sensor.

Several studies are conducted to explain the texture, as well as the magnetic and structural propertie of the IrMn/CoFe exchange bias systems. The microstructure of the systems is shown to be highly dependent on the anisotropy constant.

Several experimental measurements are conducted to explain the antiferromagnet activity taking place in the different exchange bias systems. The correlation existing between the exchange field and the distribution of grain volumes of the system is also analyzed.

Several first-principles density functional calculations are conducted to explain the intrachain antiferromagnetic interaction and the electronic structure exhibited by the [Sr.sub.3]NiIr[O.sub.6] compounds.

The article explains the magnetic, thermal and the electrical properties of the different single-crystal [J.sub.eff] = 1/2 Mott insulator [Sr.sub.2]Ir[O.sub.4. The presence of a low magnetic/ferroelectric state is shown to lead to the generation of a big magnetoelectric effect.

Several analyses are conducted to explain the effects of heating pulse width and antiferromagent thickness on the write power density of the IrMn and FeMn compounds. Lower thickness is shown to lead to low write power density.

Magnetization versus magnetic field measurements at several temperatures were used to analyze the IrMn/Co/NM/[Ni.sub.81][Fe.sub.19] spin valves, with the nonmagnetic (NM) spacers of Ru and Cu grown by sputtering. The analyses results provided quantitative values of both contributions and revealed that the oscillatory coupling mechanism dominates in the system with Ru spacer, while the Neel coupling mechanism dominates for the Cu spacer.

The magnetization profile of Ir in a MnIr/CoFe exchange bias system is examined by x-ray resonant magnetic reflectivity at Ir [L.sub.3] absorption edge. A stacked multilayer sample of MgO/[[Ru/[Mn.sub.75][Ir.sub.25]/[Co.sub.70][Fe.sub.30]].sub.15]/Ru has shown that the Ir is magnetized at the MnIr/CoFe interface.

The effects of oxidation time and annealing conditions on sputter-deposited magnetic tunnel junctions with a Ti[O.sub.x] barrier are examined. High resolution electron microscopy has indicated that longer oxidation times have led to a major increase in barrier layer width and to the formation of large volumes of oxides of Co and Fe.

Several analyses are conducted to explain the thermomigration-induced magnetic degradation of current perpendicular to the plane in the spin-valve read sensors. A reduction in the read sensors value is shown to lead to a significant decrease in the magnetic degradation of the system.

The magnetic anisotropy analysis technique is employed to explain the impact of the Cu layers on the core magnetization state and exchange bias observed in the IrMn/Cu/[[Co/Pt].sub.3] multilayers. The presence of the Cu spacer thickness in the multilayers is shown to lead to a significant increase in the angle of the magnetization axis.

Several magnetization measurements are conducted to explain the magnetic interactions taking place in the IrMn/Co/Ru/NiFe spin value structures. The mechanisms observed in the weak interlayer coupling taking place in these structures.

When parahydrogen is used as a source of nuclear spin polarization, spontaneous magnetization transfer has proceeded in low magnetic field from the two nascent hydride ligands of the dihydride complex fac,cis-[Ir(P[Cy.sub.3])[(py).sub.3][(H).sub.2]]B[F.sub.4] to its other NMR active nuclei. The degree of signal enhancement in the free substrate is increased by using electronically rich and sterically encumbered phosphine ligands such as P[Cy.sub.3], P[Cy.sub.2]Ph, or P[super i][Pr.sub.r] and by optimizing the strength of the magnetic field in which polarization transfer occurs.

The interlayer exchange phenomenon in MnIr/permalloy and MnIr/CoFeB thin films is studied and network analyzer ferromagnetic resonance is used for determining the interlayer exchange field acting on the ferromagnetic layer at each point of its hysteresis loop. The exchange fields have shown that the exchange bias value extracted from the back and forth coercivities have not described the magnitude and time evolution of the interlayer exchange field upon reversal of the ferromagnet magnetization correctly.

The air-sensitive and electrochemically oxidized [Ir{ArNC(N[R.sub.2])NAr}[([C.sub.8][H.sub.14]).sub.2]] precursors ([C.sub.8][H.sub.14] = cis-cyclooctene and R = Me or Et; Ar = Ph or 4-Me[C.sub.6][H.sub.4]) were used to synthesize electron-rich tris(guanidinato) complexes of [Ir.sup.III]. The analytical and spectroscopic characterization and a single-crystal structure determination of isolable, paramagnetic [Ir.sup.IV] compounds, [Ir[{ArNC(N[R.sub.2])NAr}.sub.3]]P[F.sub.6] demonstrated the accessibility of [Ir.sup.IV] in a nitrogen-donor ligand environment.

The studies of domain structure and magnetization reversal process of exchange-coupled ferromagnet/antiferromagnet bilayers Co(x)/Ir-Mn(10 nm) as a function of both thickness of the Co layer and annealing temperature is presented. The domain size of the structure decreased rapidly for high annealing temperatures, while the results from x-ray diffraction indicated no significant change in the crystallographic texture.

A laser-assisted tomographic atom probe is used for structural characterization of [Ta.sub.3] nm/[[[([Pt.sub.2] nm/[Co.sub.0.4] nm).sub.3]/[Pt.sub.x]/Ir[Mn.sub.7] nm].sub.7]/[Pt.sub.10] nm multilayers without (x=0 nm) and with (x=0.4 nm) a Pt spacer. The diffusion of Ir and Mn atoms into the Co layer which is prevented by the Pt spacer that acts as a diffusion barrier and the consequences of such effect on the magnetic properties of multilayer is also discussed.

In tetragonally distorted [Fe.sub.0.5][Co.sub.0.5] alloy films grown epitaxially on Pd(001), Ir(001) and Rh(001) substrates the crystal field has located the electronic states near the Fermi level ([E.sub.F]) with one being below [E.sub.F] and the other above [E.sub.F] with an energy separation smaller than in bulk nondistorted material. This has resulted in a strong uniaxial anisotropy and an easy magnetization axis perpendicular to the film plane up to the thickness up to which the films have remained tetragonally distorted.

The correlation between the exchange bias strength and magnetic domain structure in ferromagnetic (AF) bilayers is clarified by observing ferromagnetic domain structure at Co-[L.sub.3] edge for polycrystalline Mn-Ir/Co-Fe bilyares by using the x-ray magnetic circular dichroism photoelectron emission microscopy method. The studies have shown that the larger size of AF domain, which means small distribution of fixing direction of AF spins, has induced the large exchange bias field.

The reorientation of exchange anisotropy in the epitaxial (002) IrMn/CoFe bilayers is examined. The transitions of exchange-bias field from a negative field to a positive field with increasing time scale are observed and the double-shifted magnetization curve in this system is used as an indicator for the relaxation of interfacial spins of IrMn.

The exchange bias effects in arrays of Cu/NiFe/IrMn/Cu nanoscale antidot arrays prepared by deep ultraviolet lithography are examined. The enhancement in the exchange bias field is attributed to the physical limitations imposed on the IrMn domain size by the reduced lateral dimensions of the antidots.

The advantages of an antiferromagnetic iridium-manganese intermediate layer directly under the perpendicular magnetic recording layer are described. The mechanisms through which the IrMn layer has affected the thermal stability are discussed.

The current induced magnetization reversals on the free layer of patterned spin valve ellipse are examined by using differential magnetoresistance (MR) measurements, in which various direct currents are superimposed to alternating current for the MR measurements. The magnetization transitions between metastable states are realized in the dc scanned MR loop, in which the resistance levels are identified in accordance with the field scanned MR loop.

Point-contact based studies of the effect of a large current density on the exchange bias at antiferromagnet/ferromagnet (AFM/FM) interfaces are extended to a new antiferromagnetic alloy, IrMn. A negative current density injected through the F=CoFe into an IrMn/CoFe interface has increased the exchange bias, while the positive current has decreased it.

The irradiation of IrMn-based spin valves with 550 eV hydrogen ions has increased their giant magnetoresistance and exchange bias. The results showed that the hydrogen ion irradiation with low energy is robust method to modulate electrical and magnetic properties of spin switching devices without significant degradation in the performance or the microstructures.

The time and temperature dependences of the exchange field achieved by control of the setting conditions in CoFe/IrMn exchange couples are examined. The results are consistent with an independent antiferromagnetic (AF) grain model where each grain has reversed via a process analogous to a Stoner-Wohlfarth rotation mechanism rather than an AF domain model.