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Dual IrMn-pinned current-perpendicular-to-plane giant magnetoresistive sensor structures have been investigated, and their signal and noise characteristics are compared to similar standard single sensors, using test structures with sizes down to 50 nm. The intrinsic signal ΔRA product is found to be increased by a factor of nearly 2 between single and dual spin valves, although the parasitic resistance due to the second 80-nm-thick IrMn-pinned layer stack limits the net increase in ΔR/R to a factor of 1.5. For the single spin valve with antiparallel free and reference layers, the noise power spectral density shows a large asymmetry between positive and negative current flows due to strong spin-torque effects for positive (electrons flow from reference layer to free layer) current densities above 1×107A/cm2. For the dual sensor, however, the critical current density is symmetric in polarity and is increased to above 5×107A/cm2, resulting in a 5-fold increase in practical sensor output voltage. [ABSTRACT FROM AUTHOR]

The magnetoresistance of current perpendicular to the plane spin-valve sensors with antiparallel coupled pinned layers utilizing Ir as an AP coupling layer was measured as a function of reference layer thickness. Ir-coupled antiparallel pinned structures exhibit extremely high coupling energies in excess of 3 ergs/cm2, allowing for an increase of the thicknesses of both the pinned layer and reference layer to more than 100 Å while maintaining both high saturation fields and a moment-balanced antiparallel pinned structure desirable for stable read sensors. The spin valves were patterned into pillars with diameters ranging from 50 to 200 nm by using a combination of electron beam lithography and ion milling. The magnetoresistance increases from 2.2% to 4.0% by increasing the reference layer thickness from 30 to 110 Å, which is in agreement with the Valet-Fert model in the long spin-diffusion length limit. [ABSTRACT FROM AUTHOR]

Time resolved scanning Kerr microscopy has been used to study the response of square Ni88Fe12/Co80Fe20 bilayer elements to a pulsed magnetic field. Measurements were performed upon a square element of 6000 nm size and upon 64, 120, 220, 425, and 630 nm square elements that formed square arrays of about 4000 nm total size. While the frequency of precession of the magnetization of the 6000 nm element could be described with a macrospin model, the frequencies observed in the arrays of submicron size elements differed from the macrospin prediction. This observation may be understood in terms of the increasing nonuniformity of the demagnetizing field as the element aspect ratio is decreased. [ABSTRACT FROM AUTHOR]

The properties of magnetic tunnel junctions with aluminum oxide barriers alloyed with boron are presented. When aluminum is deposited by sputtering, 10 at. % B addition is sufficient to completely transform the deposited Al film from crystalline to amorphous. We have investigated if the deposition of amorphous AlB prior to oxidation results in a variation of tunnel-valve properties. It is found that ultrathin Al[SUB90]B[SUB10] films can be readily oxidized using a procedure similar to that for Al films, resulting in tunnel valves with good magnetic properties. In the ultrathin regime (when the specific junction resistance is R[SUBj]<20 Ω μm[SUP2]), the barriers with boron yield magnetoresistance values slightly above that of pure aluminum oxide, although the effect is not significant for R[SUBj]<5 Ω μm[SUP2]). [ABSTRACT FROM AUTHOR]

Ferromagnetic resonance (FMR) in the Co[SUB80]Fe[SUB20]/Ni[SUB80]Fe[SUB20] free (sense) layer of micron-sized, magnetic tunnel junction (MTJ) devices is studied by two different techniques. The first method employs the MTJ device's magnetoresistance, and measures thermally excited magnetization fluctuations (mag-noise) as a resistance noise spectrum. Correlations between magnetoresistance and FMR frequency versus in-plane magnetic field have been observed for different devices. The FMR frequencies agreed well with calculations when including substantial out-of-plane magnetic anisotropy fields. The second method detects the change in the complex impedance of the MTJ before and after applying a dc current, as measured by a vector network analyzer. The latter method seems to be very sensitive to internal nonuniform states of the free layer magnetization. [ABSTRACT FROM AUTHOR]

Nonoxide tunnel barriers such as AlN are of interest for magnetic tunnel junctions to avoid the oxidation of the magnetic electrodes. We have investigated the fabrication and properties of thin AlN-based barriers for use in low resistance magnetic tunnel junctions. Electronic, magnetic and structural data of tunnel valves of the form Ta (100 Å)/PtMn (300 Å)/CoFe[sub 20] (20 Å-25 Å)/barrier/CoFe[sub 20] (10-20 Å)/NiFe[sub 16] (35-40 Å)/Ta (100 Å) are presented, where the barrier consists of AlN, AlN[sub x]O[sub y] or AlN/AlO[sub x] with total thicknesses between 8 and 15 Å. The tunnel junctions were sputter deposited and then lithographically patterned down to 2x2 μm[sup 2] devices. AlN was deposited by reactive sputtering from an Al target with 20%-35% N[sub 2] in the Ar sputter gas at room temperature, resulting in stoichiometric growth of AlN[sub x] (x=0.50±0.05), as determined by RBS. TEM analysis shows that t! he as-deposited AlN barrier is crystalline. For AlN barriers and AlN followed by natural O[sub 2] oxidation, we obtain tunnel magnetoresistance >10% with specific junction resistance R[sub j] down to 60 Ωμm[sup 2]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have investigated the use of ultrathin Al[sub 2]O[sub 3] barriers to fabricate low-resistance tunnel-valve sensors suitable for recording heads. Tunnel valves of the type underlayer/(IrMn or PtMn)/CoFe/Al[sub 2]O[sub 3]/CoFe/NiFe/Cap layer have been fabricated by magnetron sputtering. Tunnel barriers are formed by Al metal deposition followed by in situ oxidation, and tunnel-junction test devices are built by photolithography with areas down to 1x1 μm[sup 2]. Specific resistances as low as 13 Ω μm2 with 25% tunnel magnetoresistance have been obtained using Al thicknesses of 6-7 Å. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Individual layers of Ni[sub 0.8]Fe[sub 0.2], Ni[sub 0.8]Fe[sub 0.13]Co[sub 0.07], TaN, and CrSi, and a full magnetic random access memory stack consisting of NiFeCo/CoFe/Cu/CoFe/NiFeCo/TaN/CrSi multilayers, were etched in high density Cl[sub 2]/Ar plasmas either with or without concurrent ultraviolet (UV) illumination. Under optimized conditions, etch rate enhancement up to a factor of 5 was obtained for NiFeCo, TaN, and CrSi with UV illumination; whereas the etch rate of NiFe was retarded. Post-etch cleaning with H[sub 2] or SF[sub 6] plasmas or H[sub 2]O rinsing was necessary in all cases in order to prevent corrosion of the metal layers from chlorinated etch residues. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated the low-temperature magnetic and magnetotransport characteristics of CoFeB/Cu/CoFeb/FeMn amorphous magnetic spin valves. Experimental details; Experimental results; Conclusions.

Presents a study that fabricated face-centered cubic Co[subx]Pd[sub1-x] alloy films by molecular beam epitaxy. Methodology; Results; Conclusion.

Presents a study on the development of ultrafine face-centered-cubic cobalt in a conducting copper matrix by annealing of sputtered metastable Co[subx]Cu[sub1-x] alloy films. Experimental method; Results; Conclusions.

Studies magnetic properties of the spinel phase for iron[subx]copper[1-x]rhodium[sub2]selenium[sub4]. Method of the study; Results and discussion; Concusion.

Presents a study which examined the consequence of structure on the magnetic properties of 304 stainless steel in two distinct crystalline states. Experimental procedures; Results and discussion; Conclusion.

Deals with a study which described an epitaxial spin-valve-type system for low-field magnetoresistive (MR) detection. Information on sensitive magnetic field sensors; Data on MR response; Details on hysteresis loops.

Details a study which investigated the structural and magnetic properties of metastable gadolinium-chromium alloys prepared by direct current magnetron sputtering. Preparation of the study population; Representative x-ray diffraction patterns of the alloys; Relationship between magnetization and temperature.

Presents a study that fabricated iron(Fe)(110)/silver(Ag)(111) superlattices with Ag layer thicknesses of 30 or 60 Å and various Fe layer thicknesses by high-rate sputtering. Advantages of metallic superlattices of Fe/Ag; Representative diffraction data; Diffraction pattern of an ideal superlattice.