Search

Magnetic and magnetotransport properties of current-perpendicular-to-the-plane (CPP) giant-magnetoresistance (GMR) spin-valve sensors containing the Heusler alloy Co2MnGe are presented. The geometrical and head integration constraints which exist for recording head applications are discussed and dictate various design compromises which determine the final device properties. Here we show that even for small total sensor thicknesses 400 Å and anneal temperatures < 250 °C we can obtain CPP-GMR signal levels up to ΔRA = 4 mΩ-μm2 at room temperature when inserting Co2MnGe in both the free layer and reference layers of the spin valve. Output levels increase to 10 mΩ-μm2 when reducing the temperature below 100 K, demonstrating the strong temperature dependence of the spin-dependent scattering in the Co2MnGe-based magnetic layers. [ABSTRACT FROM AUTHOR]

The magnetotransport properties of current perpendicular to the plane giant magnetoresistive spin valves utilizing (CoxFe100-x)100-yAly alloys are investigated over a wide alloy composition range. (Co50Fe50)75Al25 is determined to be the approximate alloy composition that maximizes magnetoresistance. An increase in magnetoresistance from 1.7% for spin valves with standard Co50Fe50 to 3.3% for spin valves with (Co50Fe50)75Al25 is observed when substituting the same “magnetic” thickness in both the reference and the free layers. The spin-diffusion length for (Co50Fe50)75Al25 is determined to be less than approximately 35 Å. Spin-torque measurements show that the spin-torque current density threshold is lower in CoFeAl spin valves compared to standard CoFe spin valves. [ABSTRACT FROM AUTHOR]

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.

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.

Doping ferromagnetic nickel–iron alloys with chromium causes the Curie temperature to be reduced. We have demonstrated that solid state solutions of Ni–Fe–Cr can be formed by implanting Cr ions into ferromagnetic NiFe alloy films, thus creating paramagnetic films. We find that the magnetic moment and coercivity decrease steadily with Cr+ dose, reaching zero at room temperature with the onset of paramagnetism. Using Cr+ implantation in conjunction with a lithographic mask we have patterned continuous Ni80Fe20 films into separate regions that are ferromagnetic and paramagnetic at room temperature. This magnetic patterning process may have applications for the manufacture of magnetic write heads, such as for the notching process used to constrain the stray field from the write gap. [ABSTRACT FROM AUTHOR]

The magnetic relaxation of 10 and 50 nm thin films of (CoFe)100-xGex (0 at. %≤x≤35 at. %) alloys was investigated by broadband ferromagnetic resonance (FMR) experiments. 10 nm thin films exhibit a significant two magnon contribution to the FMR linewidth. The 50 nm films exhibit very low damping constants of α≈0.0025 and relaxation rates as low as 33 MHz in the composition range of 20 at. %≤x≤30 at. % Ge after annealing. Structural characterization revealed B2 order for these compositions. First principles calculations confirm a pseudogap in the minority channel for B2 ordered (CoFe)75Ge25 which may cause the low damping parameters and high ΔRA in CoFeGe based current perpendicular to the plane giant magnetoresistance spin valves. [ABSTRACT FROM AUTHOR]

The magnetic and corrosion properties of Ir[sub 16]Mn[sub 84] with Ru and Cr additions have been studied. Spin valves with Ir[sub 16]Mn[sub 84]-Ru have slightly lower H[sub ex] and T[sub b] than when pure Ir[sub 16]Mn[sub 84] is used. The corrosion properties improve, H[sub ex] and T[sub b] improve with 3 vol % Cr, but drop considerably with more Cr additions, losing 21% of the pure IrMn value by 12 vol % Cr. The corrosion current and potential are I[sub c] = 8 µA/cm² and E[sub 0] = -580 mV respectively, for Ir[sub 16]Mn[sub 84] with 12 vol % Cr. This represents a significant improvement over pure Ir[sub 16]Mn[sub 84], which has I[sub c] = 100 µA/cm² and E[sub 0] = -1300 mV. When Ru is used as the additive, I[sub c] and E[sub 0] are 10 µA/cm² and - 100 mV, respectively, for 9 vol %. Cr is the superior additive, especially in small concentrations where it shows a significant decrease in the I[sub c] without degrading the magnetic properties. [ABSTRACT FROM AUTHOR]

X-ray diffraction (XRD), magnetometry, and ferromagnetic resonance (FMR) measurements were performed on sputtered thin films of the nominal Heusler alloy (Co2Mn)1-xGex with varying Ge content and annealing temperatures. XRD indicates some degree of B2 alloy formation, with strong (110) texturing. FMR measurements were performed in a perpendicular geometry that minimized the contribution of two-magnon scattering to the linewidth. The FMR data indicate a significant increase in linewidth for samples that lack a well-defined (220) peak, presumably as a result of inhomogeneous line broadening. Samples annealed at 200?°C exhibit decreasing Landau-Lifshitz damping with increasing Ge content, while samples annealed at 245 and 300?°C have a nonlinear dependence of linewidth on frequency. The nonlinear component of the linewidth data was successfully fit with a generalized theory of slowly relaxing impurities, originally proposed by Van Vleck and Orbach. The modified theory includes the possibility of transverse coherence during the relaxation process. Magnetometry and FMR spectroscopy results were analyzed in the context of Malozemoff's generalized Slater-Pauling (GSP) theory, with the conclusion that the Ge sites support a significant negative-polarized spin density of several tens of percent. The GSP analysis results were consistent with a more conventional analysis of the spectroscopic g-factor that is appropriate for alloys. The proportionality of the strength of the slow-relaxer contribution to the damping suggests that the negatively polarized Ge atoms are acting as the slowly relaxing impurities in question. [ABSTRACT FROM AUTHOR]