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We demonstrate that the spectroscopic g-factor can be determined with high precision and accuracy by broadband ferromagnetic resonance measurements and by applying an asymptotic analysis to the data. Spectroscopic data used to determine the g-factor are always obtained over a finite range of frequencies, which can result in significant errors in the fitted values. We show that by applying an asymptotic analysis to broadband datasets, precise values of the intrinsic g-factor can be determined with errors well below 1%, even when the exact form of the Kittel equation (which describes the relationship between the frequency and resonance field) is unknown. We demonstrate this methodology with measured data obtained for sputtered Ni80Fe20 (Permalloy) thin films of varied thicknesses, where we determine the bulk g-factor value to be 2.109 ± 0.003. Such an approach is further validated by application to simulated data that include both noise and an anisotropy that is not included in the Kittel equation that was used in the analysis. Finally, we show a correlation of thickness and interface structure to the magnitude of the asymptotic behavior, which provide insight into additional mechanisms that may lead to deviations from the Kittel equation. [ABSTRACT FROM AUTHOR]

We report on the effect roughness has on the magnetic properties of Co/Ni multilayers with perpendicular anisotropy. We can systematically vary the surface roughness and grain size by the variation in the Cu seed layer thickness. The roughness has a significant effect on the lateral anisotropy variation across the material, which was studied through the size dependence of the switching field and switching field distribution in nanostructures. Ferromagnetic resonance measurements show a large dependence of the linewidth on the topography. However, only the inhomogeneous linewidth broadening varied significantly with roughness with little to no effect on the intrinsic damping parameter of α=0.015-0.018. [ABSTRACT FROM AUTHOR]

We use broadband ferromagnetic resonance spectroscopy and x-ray diffraction to investigate the fundamental origin of perpendicular anisotropy in Co90Fe10/Ni multilayers. By careful evaluation of the spectroscopic g-factor, we determine the orbital moment along the out-of-plane and in-plane directions. For the multilayers, we find a direct relationship between the orbital moment asymmetry and the perpendicular anisotropy, consistent with the theory of Bruno [Bruno, Phys. Rev. B 39, 865 (1989)]. A systematic x-ray diffraction study revealed the presence of a trigonal strain as high as 0.7% in some samples. However, we found no direct correlation between the strain and the anisotropy, indicating that the anisotropy is not dominated by magnetoelastic effects. To further study the interface structure on the anisotropy, we prepared a set of equivalent alloy samples. The strain in the alloy samples was comparable to that of the multilayer samples; however, the orbital moment asymmetry in the alloy samples showed a very different trend, allowing us to isolate the effect of the interfaces in the multilayers. [ABSTRACT FROM AUTHOR]

We performed a systematic study of damping in Co90Fe10/Pd multilayers by use of broadband (1-60 GHz) ferromagnetic resonance (FMR) spectroscopy in the perpendicular geometry. The data were fitted with the conventional Landau-Lifshitz equation in conjunction with an inhomogeneous contribution to linewidth δH0. Samples were prepared with net perpendicular anisotropy field values ranging from --0.5 to +1.2 T. δH0 shows a dependence on the perpendicular anisotropy, though the Landau-Lifshitz damping parameter &agr;, which ranged from 0.016 to 0.04, exhibits no trend as a function of anisotropy. We explain the wide variation of &agr; as a result of spin pumping from Co90Fe10 into adjacent nonmagnetic layers. We use a quantitative model for spin pumping that includes the intrinsic spin-mixing conductance at the Co90Fe10/Pd interface and the spin-diffusion length of Pd, which were experimentally measured at room temperature to be (1.07 ± 0.13) x 1019 m-2 and 8.6 ± 1.0 nm, respectively. We quantitatively show how a is enhanced by spin pumping through an FMR investigation of individual Pd/CoFe/Pd, and Pd/CoFe/Pd/CoFe/Pd layer structures [ABSTRACT FROM AUTHOR]

Abstract: We used Brillouin light scattering and magneto-optical Kerr effect measurements to study the magnetic properties of ultra-thin 1.5nm Fe layers undergoing various annealing and high temperature growth processes on GaAs(001). We found that the thermal processing has a profound effect on the form and magnitude of the magnetic anisotropy and value of the coercivity. In addition, in situ scanning tunneling microscopy revealed that high temperature post-deposition annealing results in the formation of rectangular pits, while high temperature growth results in a rough faceted microstructure. [Copyright &y& Elsevier]

We used perpendicular ferromagnetic resonance to measure the damping parameter in Co90Fe10/Ni multilayers over a wide range of layer thicknesses. The magnetic anisotropy within this range varied from in-plane to out-of-plane. We measured (Co90Fe10)xNi1-x alloys of identical thicknesses over the same compositional range of Co90Fe10 and Ni in order to isolate the influence of the multilayer structure. The damping parameter varied from 0.004 to 0.030 and depended only on the relative amounts of Co90Fe10 and Ni and was independent of the magnetic anisotropy and layer structure. [ABSTRACT FROM AUTHOR]

We developed the thin film microwave magnetic material, M-type barium hexagonal ferrite (BaM) doped with Al, for signal processing devices operating above 40 GHz with little to no applied magnetic field. Al was chosen as the dopant material because it significantly increases the already strong anisotropy field of BaM. A series of thin film BaAlxFe12-xO19 samples, x ranging from 0 to 2 in 0.25 steps, were deposited on Pt templates using a metal-organic decomposition growth technique. The resulting films are polycrystalline and highly textured, with the hexagonal c-axis directed out of plane. These films are also self-biasing; easy axis hysteresis loops have a high squareness ratio, s, in the 0.83-0.92 range. As expected, the anisotropy field increases with x, ranging from 1.34 to 2.19 × 106 A/m (16.9-27.5 kOe) for x = 0-2, while the saturation magnetization Ms decreases with x, ranging from 0.334 to 0.175 × 106 A/m (4πMs = 4.2-2.2 kG) for x = 0-2. These values were measured at room temperature, but the temperature dependence of these quantities was also measured below room temperature, down to 30 K. The measured ferromagnetic resonance linewidths, on the order of 12-30 × 103 A/m (140-370 Oe) for compositions below x = 1, indicate device-quality films. Above a certain threshold, the linewidth increases linearly with frequency at a rate of 0.2-0.64 × 103 (A/m)/GHz (2.5-8 Oe/GHz) for x = 0-1, respectively. The behavior of the linewidth is correlated with the structural properties of the films measured using x-ray diffraction and atomic force microscopy. The results of magnetic force microscopy, Curie point measurements, spectral ellipsometry (index of refraction), and magneto-optical measurements are also included and discussed. [ABSTRACT FROM AUTHOR]

In (Co/Pd)n multilayer dots with submicrometer diameters, it is understood that reversal is initiated by the nucleation of a small reversed region, followed by uninhibited expansion of the nucleus. The fact that the reversed domain expands will relative ease has been attributed to the fact that the field required to free a domain wall is much smaller than the field required to create the nucleus. In this work, we measured the angular dependence of the coercivity in individual 500-nm and 1-µm (Co/Pd)n multilayer dots and show that the shape of this curve deviates from the Stoner-Wohlfarth-like form observed by others. We attribute this deviation to (1) the domain-wall repining field exceeding the nucleation field when the reversal field has a large in-plane component and (2) exchange-spring-like behavior at the dots' edges due to ion-mill damage. [ABSTRACT FROM AUTHOR]

The structure and static magnetic properties--saturation magnetization, perpendicular anisotropy, spectroscopic g factor, and orbital magnetization--of thin-film 3d transition metal alloys are determined over the full range of alloy compositions via x-ray diffraction, magnetometry, and ferromagnetic resonance measurements. We determine the interfacial perpendicular magnetic anisotropy by use of samples sets with varying thickness for specific alloy concentrations. The results agree with prior published data and theoretical predictions. They provide a comprehensive compilation of the magnetic properties of thin-film NixCo1-x, NixFe1-x, and CoxFe1-x alloys that goes well beyond the often-cited Slater-Pauling dependence of magnetic moment on alloy concentration. [ABSTRACT FROM AUTHOR]