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Motivated by the importance of magnetization dynamics in nanomagnets for the development and optimization of magnetic devices and sensors, we measured and modeled spin wave spectra in patterned elliptical nanomagnets. Ferromagnetic resonance spectra for multiple nanomagnets of Ni80Fe20, fabricated by electron-beam lithography to have nominal short-axes of 200 nm or 100 nm, were measured by use of heterodyne magneto-optical microwave microscopy. Scanning electron microscope images taken of the same nanomagnets were used to define element shapes for micromagnetic simulations. The measured spectra show significant differences between nominally identical nanomagnets, which could be only partially attributed to uncontrolled shape variations in the patterning process, as evidenced by the limited agreement between the measured and simulated spectra. Agreement between measurements and simulations was improved by including a zone of reduced magnetization and exchange at the edges of the nanomagnets in the simulations. Our results show that the reduction of shape variations between individual magnetic random-access memory elements can potentially improve their performance. However, unambiguous determination of materials parameters in nanomagnets based on analysis and modeling of spin wave spectra remains problematic. [ABSTRACT FROM AUTHOR]

This paper reports effects of inter-film interactions on static and dynamic magnetization behavior at film edges in magnetic trilayer stripe arrays under transverse applied fields. The trilayers consist of two magnetic films of Ni80Fe20, 10 nm and 20 nm thick that interact via dipolar fields across thin, nonmagnetic spacers from 1 nm to 20 nm thick. These trilayer films are patterned into stripe arrays by optical interference lithography. Ferromagnetic resonance spectra exhibit separate edge modes that are identified as excitation of edge modes primarily in one magnetic film or the other. When interlayer exchange is negligible, we observe several effects of dipolar edge-edge coupling including shifts of the edge saturation fields and changes in the mode intensity ratio relative to single-film edges. These interaction effects are reproduced by micromagnetic modeling and explained by simple models. [ABSTRACT FROM AUTHOR]

We use “edge mode” ferromagnetic resonance to probe the magnetic properties of oxidized Ni80Fe20 (Py) nanostripe edges. The oxidation is carried out using either oxygen plasma or thermal annealing in an oxygen ambient. We find that for both treatments the edge saturation field decreases systematically with increasing oxidation due to reduced magnetization near the edges. However, the change of effective out-of-plane anisotropy field shows opposite trends for these two oxidation methods. Micromagnetic simulations suggest that thermally annealed samples may have an additional reduction in the bulk magnetization, possibly due to a compositional change in Py stripes. The two distinct oxidation profiles also result in different changes in resonance linewidth; we find little damping change for plasma treatment but an enhanced effective damping for thermal annealing. [ABSTRACT FROM AUTHOR]

The effects of edge roughness on vortex nucleation field and its distribution are measured in Permalloy nanostructured arrays. Teardrop-shaped elements, 250 nm wide and 30 nm thick, were fabricated using electron beam lithography and lift-off. Roughness variations were created by varying the electron dose during patterning, and measured by analysis of in-focus transmission electron microscopy (TEM) images. In situ measurements of the vortex nucleation fields and the nucleation field distributions of the dose arrays were performed with Lorentz mode TEM. In combining the measurements of edge roughness with measurements of nucleation field and its distribution, we show that edge roughness increases the probability for vortex nucleation and thus permits vortices to nucleate at larger applied fields, but at the same time, edge roughness broadens the nucleation-field distribution in magnetic nanostructured arrays. [ABSTRACT FROM AUTHOR]

The effect of doping on the magnetic damping parameter of Ni80Fe20 is measured for 21 transition metal dopants: Ti, V, Cr, Mn, Co, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, and Au. For most of the dopants, the damping parameter increases linearly with dopant concentration. The strongest effects are observed for the 5d transition metal dopants, with a maximum of 7.7×10-3 per atomic percent osmium. [ABSTRACT FROM AUTHOR]

Reports on strong anisotropy in thin magnetic films deposited on obliquely sputtered tantalum underlayers. Fitting the angular dependence of the ferromagnetic resonance field to obtain values of anisotropy field; Microstructure of spin valve; Magnetoresistive measurements of the dispersion of the hard axis directions.

Investigates the anisotropy in thin magnetic films deposited on obliquely sputtered tantalum underlayers. Anisotropy measurements; Microstructure; Homogeneity.

Presents an overview of a study on dynamics and self-organized criticality in magnetic materials. Equations of motion for the normal modes of normally magnetized thin films; Involvement of parametrically excited modes in features of the domain of auto-oscillation; Effects of degeneracy breaking in pairs of hidden modes.

We have used “trapped spin wave” or edge modes of magnetic precession to probe the magnetic environment near magnetic film edges magnetized perpendicular to the edge. Micromagnetic models of dynamics in stripes reveal that the edge mode frequency-field relationship depends on whether the edge surface is vertical or tapered, while the “bulk” modes are nearly unaffected. The models show the edge-mode frequency going to zero at the edge saturation field. This critical field becomes much less distinct for applied fields misaligned from the edge normal by as little as 1°. Ferromagnetic-resonance and Brillouin light-scattering measurements of the edge modes in an array of 480-nm-wide×12-nm-thick Ni80Fe20 stripes have a lower edge saturation field than the vertical edge models, but agree well with the model of 45°-tapered edges. [ABSTRACT FROM AUTHOR]

Micromagnetic calculations are used to determine the eigenfrequencies and precession patterns of some of the lowest-frequency magnetic normal modes of submicron patterned elements. Two examples are presented. For a Permalloy-like ellipse, 350 nm × 160 nm × 5 nm thick in zero field, the lowest frequency normal mode at 4 GHz corresponds to precession in the "ends" of the ellipse. Other resonant frequencies are compared with the frequencies of spinwaves with discrete wave vectors. For a normally magnetized 50 nm diameter × 15 nm thick cobalt disk, the calculated eigenfrequencies increase linearly with applied field, mimicking the behavior of the experimental critical current for spin transfer instabilities in an experimental realization of this disk. [ABSTRACT FROM AUTHOR]

We have achieved excellent exchange decoupling of grains in CoPd multilayers by annealing in air at 300 °C. Samples exhibit a slope in the hysteresis loop close to 1.0, nucleation fields as large as 11 kOe, and coercivities as large as 16 kOe. These are among the best properties ever achieved for CoPd multilayers. In samples of the general type seed layer\ (0.3 nm Co\1 nm Pd)×15\capping layer, it appears that atoms diffuse rapidly up and down the grain boundaries at 300 °C. From x-ray photoelectron and Auger depth profiling, we have found that when Co atoms arrive at the surface they become oxidized and remain at the surface, leaving the grain boundaries depleted in Co and apparently nonmagnetic. If the annealing is carried out in vacuum, exchange decoupling of the grains does not occur. This result supports our conclusion that the presence of oxygen plays a crucial role. When Au or Pt atoms are present in the seed layer or capping layer, they diffuse into the CoPd grain boundaries and apparently enhance the exchange decoupling of grains. [ABSTRACT FROM AUTHOR]

The extrinsic ferromagnetic resonance linewidth is modeled in a perpendicular recording media with inhomogeneous uniaxial anisotropy field Hu and with tilting of the easy axes from the film normal. The linewidth is calculated using both a local resonance model and a classical equivalent of the two-magnon model. Variations in Hu and easy axis tilting are shown to produce very different angular dependence of the linewidth, and when the two-magnon models are valid, the linewidth is also shown to depend on inter-granular exchange coupling. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Detailed ferromagnetic resonance measurements on thin Ni[SUB80]Fe[SUB20] films are described that determine characteristics of intrinsic damping and the effects of intentionally created defects on linewidth. Measurements are made as a function of frequency with magnetization oriented in-plane and normal to the plane. For nominally uniform films, the ferromagnetic resonance linewidth is linear in frequency for both in-plane and normal magnetization and is well described by Landau-Lifshitz damping with a constant damping parameter. The effect of inhomogeneity was investigated by depositing the Ni[SUB80]Fe[SUB20] films on specially prepared substrates, one with parallel, random grooves and one with polycrystalline, antiferromagnetic NiO. The linewidth in these samples is generally larger with magnetization in-plane than it is with magnetization normal. In the NiO/Ni[SUB80]Fe[SUB20] film, the in-plane linewidth is linear in frequency with a significant zero-frequency linewidth. In the Ni[SUB80]Fe[SUB20] sample on the grooved substrate, the linewidth has a more complicated frequency dependence. [ABSTRACT FROM AUTHOR]

An anomalous Hall effect (AHE) and a planar Hall effect (PHE) represent a perpendicular component and an in-plane component of the magnetization in the double-layered media. Since AHE and PHE have different symmetries regarding to the applied magnetic field H, it is easy to distinguish the AHE component, which is proportional to M, and PHE component, which is proportional to M², from the measured Hall voltage V[sub H]. The Hall voltage of the double-layered film composed of Co-Cr-Ta and Ni-Fe layers was observed when the magnetic field is applied at an angle (α) of 30° from the normal to the film plane. The perpendicular and the in-plane components, which are regarded as the magnetization process of Co-Cr-Ta and that of the Ni-Fe layer, respectively, can be easily determined from these characteristics. The Hall measurement is useful to study the magnetization characteristics in the double-layered media. [ABSTRACT FROM AUTHOR]

The magnetic field determined from vanishing rotational hysteresis loss of CoCrPtB perpendicular thin film media was experimentally investigated. It was clarified that (1) in Co[sub 72]Cr[sub 16]Pt[sub 8]B[sub 4] media with d[sub mag] of less than 200 nm and Co[sub 64]Cr[sub 24]Pt[sub 8]B[sub 4] media with d[sub mag] of less than 100 nm, a homogeneous structure was realized, except for the existence of an initial growth region. (2) For both media, the perpendicular rotational hysteresis loss, W[sub r], the maximum field of W[sub r], H[sub p], and the field where W[sub r] = 0, H[sub W][sub r=0], increased with an increase in d[sub mag]. (3) For both media, H[sub W][sub r = 0] / H[sup grain][sub k] increased with an increase in d[sub mag] and saturated at a magnitude of about 1. (4) For the medium with thin magnetic film thickness, at applied field of H[sub W][sub r=o] < H < H[sup grain][sub k], a multidomain state was realized in the torque measurement in spite of no observation of loss of rotational hysteresis. This is considered to be due to the existence of thermal agitation between the multidomains. [ABSTRACT FROM AUTHOR]

It has recently been found that large uniaxial anisotropy fields in excess of 120 kA/m (1500 Oe) can be created in thin (3-5 nm) films of Co by obliquely sputtered Ta underlayers. This anisotropy can be used to pin the bottom film of a spin valve while having only a modest effect on the top "free" film, separated by a 2.5 nm Cu spacer layer. This article describes measurements of thermal stability in these Ta-pinned spin valves. Using room temperature giant magnetoresistance (GMR) as a measure, we find that the structure is stable under cumulative 20 min anneals at 25 °C intervals up to 300 °C; GMR decreases to zero upon further anneals up to 450 °C. Measurements taken at elevated temperatures reveal that GMR decreases linearly with temperature, extrapolating to zero at approximately 425 °C, while the anisotropy field is much less temperature dependent, remaining nearly constant up to 150 °C and gradually decreasing to 50% of its room temperature val! ue at 325 °C. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report results for μMAG standard problem No. 4, a 500 nmx125 nmx3 nm rectangle of material with properties to mimic Permalloy. Switching dynamics are calculated for fields applied instantaneously to an initial s state: Field 1 at 170° and Field 2 at 190° (-170°) from the positive long axis. Reversal in Field 1 proceeds by propagation of end domains toward the sample center. Reversal in Field 2 involves rotation of the end domains in one direction while the center of the particle rotates in the opposite direction, resulting in collapsing 360° walls with complex dynamics on fine length scales. Approaching the static coercivity, H[sub c], in small field steps, we find that the ring down frequency, f, and susceptibility, χ, are in approximate agreement with a single spin model that predicts f∝(H[sub c]-H)[sup 1/4] and χ∝(H[sub c]-H)[sup -1/2]. We show a correlation between the modes of oscillation that become unstable at the critical ! field and the switching behavior. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The preparation and measurement of nickel spheres for use in the calibration of magnetometers are described. The absolute value of the magnetic moment of a set of these spheres near room temperature was measured using the Faraday method. The variations of moment for temperatures near room temperature and for applied fields between 0.3 and 5 T were also determined. [ABSTRACT FROM AUTHOR]

Because the memory of the bias direction is carried by the antiferromagnetic order in exchange biased films, the stability of the antiferromagnetic order is critical to the existence of the exchange bias field. Ferromagnetic resonance was used to measure the relaxation behavior of polycrystalline CoO films coupled to films of Ni[sub 80]Fe[sub 20], probing the system on the time scale of the experiment, approx. 10[sup 3] s, and the time scale of the magnetic precession, approx. 10[sup -10] s. Unidirectional anisotropy (exchange biasing) and isotropic resonance field shifts are observed at the lowest temperatures. Above the apparent exchange bias blocking temperature, isotropic resonance field shifts persist. At still higher temperatures, diminishing resonance field shifts are accompanied by peaks in the FMR linewidth. The results highlight the effects of varying relaxation rates in the CoO relative to the two experimental time scales. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In magnetic random access memory, power consumption depends on the coercivity of the magnetic elements in the memory cells. In this article a new method is described that uses a “domain wall trap” element shape to reduce both the coercivity and the dependence of coercivity on element size in submicron magnetic elements. Micromagnetic simulations of a shaped permalloy element show coercivity less than one tenth the coercivity calculated for a rectangular permalloy element of the same size. The switching times for the domain wall traps are shown to be comparable to those of rectangular elements. [ABSTRACT FROM AUTHOR]

Focuses on a study which presented Monte Carlo simulations of the magnetocaloric effect in superferromagnetic clusters having uniaxial magnetic anisotropy. Background on magnetocaloric effect; Calculations and results; Conclusion.

Presents a study which described a method for determining both magnetorestriction and elastic modulus by ferromagnetic resonance (FMR). Theoretical background; Experimental procedure; Results of the study.

Focuses on a study that calculated Henkel plots using a hysteresis model base on independently moving domain walls. Background on Henkel plots; Computational procedure used; Results and discussion.

Deals with a study which described the fluctuations in the domain-wall energies, in terms of an ensemble of stochastic Langevin functions, to represent the multiplicity of metastable states in a bulk ferromagnetic materials with domain-wall pinning effects. Experimental and computational investigation into the Barkhausen effect and hysteresis properties in steel; Methodology of the study; Results and discussion.

Deals with a study which focused on the role of magnetic anisotropy in the magnetocaloric effect. Factor considered in the choice of optimizing the magnetocaloric properties of a material; Entropy change associated with applying the magnetic field; Features of the Monte Carlo calculations.

Reports on the field-induced adiabatic magnetic entropy change of a series of iron-substituted gadolinium garnets which have the potential to increase the working temperature range or to reduce field requirements of cryogenic magnetic refrigeration. Significance of a thermodynamic Maxwell relation; Preparation of the samples; Performance of electron paramagnetic resonance/ferromagnetic resonance measurements.

Reports on the field and power dependence of auto-oscillations in yttrium-iron-garnet films. Domains of oscillatory behavior due to individual resonance modes; Mechanism for the oscillations observed in the experiment; Typical frequencies of auto-oscillatory behavior in the simulation.

A vortex gyrating in a magnetic disk has two regimes of motion in the presence of disorder. At large gyration amplitudes, the vortex core moves quasi-freely through the disorder potential. As the amplitude decreases, the core can become pinned at a particular point in the potential and precess with a significantly increased frequency. In the pinned regime, the amplitude of the gyration decreases more rapidly than it does at larger precession amplitudes in the quasi-free regime. In part, this decreased decay time is due to an increase in the effective damping constant and in part due to geometric distortion of the vortex. A simple model with a single pinning potential illustrates these two contributions. [ABSTRACT FROM AUTHOR]

We have identified an important microstructural origin of the switching field distribution (SFD) in patterned Co/Pd multilayer nanodots. In this study, we patterned a marked array of 115 nm Co/Pd nanodots on 50-nm-thick Si3N4 substrate. We identified the dots with unusually small and large (>2 standard deviations of the mean) switching fields with magnetic force microscopy, followed by microstructural characterization of the same dots with transmission electron microscopy (TEM). From electron diffraction, we found that most nanodots with small switching fields have strong (200) spots, whereas those with large switching fields lack these spots. While bright-field TEM images reveal an average grain size of 7 nm, dark-field images of the (200) spots reveal on average, a single grain of >10 nm in lateral dimensions. Since we observed a direct correlation between strong (200) reflections and small reversal fields, we conclude that the largest grain in each nanodot, with an in-plane [001] is the likely cause for premature switching, which in turn defines the SFD of this array. [ABSTRACT FROM AUTHOR]

This paper presents an edge field correction for micromagnetic computations of arbitrarily shaped objects on rectangular grids. The correction is compatible with fast Fourier transform techniques and involves factors that are precomputed using the standard self-magnetostatic algorithms applied on a local, refined mesh. To evaluate this correction, we introduce a quantitative measure that is based on calculating an edge mode resonance for different orientations of an edge with respect to the rectangular mesh. Applied to a 350-nm Permalloy square, we find up to a 50% frequency shift for the uncorrected approach, but less than a 5% shift using the proposed method. We also study vortex expulsion in a 220-nm Permalloy square, and again find that the proposed correction significantly reduces the dependence of the expulsion field on the orientation angle of the sample square with the mesh. [ABSTRACT FROM AUTHOR]

Two vector magnetometry techniques are described for characterizing the magnetic properties of the edges in long, straight magnetic stripes. The critical transverse field at which the edge magnetization saturates is determined by measuring hysteresis loops as a function of angle. The angular dispersion in the stripe edge direction is estimated from the remanence by measuring the angular width of the transition from one stability direction to the other. Experimental results are presented for two samples prepared through different lithography processes. These are compared to micromagnetic modeling results for both 90° and tapered edges. Differences between measured and modeled results are likely due to thermal fluctuations and edge defects. [ABSTRACT FROM AUTHOR]

We have found that preoxidation of the bottom electrode prior to deposition of Al2O3 or MgO is very effective as a general approach to suppressing orange-peel coupling in magnetic tunnel junctions. When orange-peel coupling is suppressed, the hard-axis saturation field of the free layer is greatly reduced. [ABSTRACT FROM AUTHOR]

We have found that preoxidation of the bottom Co electrode in magnetic tunnel junctions (MTJs) very effectively suppresses orange-peel coupling. The result is a free layer that is much softer. Work by others has demonstrated that preoxidation is compatible with high-quality MTJ fabrication. [ABSTRACT FROM AUTHOR]

Presents a study that determined the normal modes and ferromagnetic resonance linewidth of an inhomogeneous thin film. Examination of the density of states profile of the thin film; Analysis of the intensity of rediagonalized eigenmodes; Information on the diagonalization of perturbed Hamiltonian system.

Presents a correction to the article, entitled 'Strong anisotropy in thin magnetic films deposited on obliquely sputtered Ta underlayers'.

Presents calculations of head to head domain wall structures in magnetic strips of Ni80Fe20 with varying widths and thicknesses. Calculation method; Results and discussion.

Presents an abstract of the study 'Nonlinear Dynamics of Magnetoexchange Modes in YIG Films.'

Grazing incidence x-ray reflectometry has been used to study surface oxidation as a diffusion barrier for Al deposited on ferromagnetic metals (Co, Fe, Ni, and Ni[sub 80]Fe[sub 20]). Samples of the form SiO[sub 2]\10 nm X\4 nm Al with X=(Co, Fe, Ni, and Ni[sub 80]Fe[sub 20]) were investigated for X\Al intermixing. Surface oxidation was achieved by exposing the ferromagnetic layer to O[sub 2] to oxidize the top two or three atomic layers before depositing the Al layer. Specular x-ray scans were used for the analysis. Samples of the form SiO[sub 2]\10 nm X\4 nm Au were used to separate topographical roughness from intermixing. Surface oxidation was found to suppress the diffusion of Al into Co, Ni, and Ni[sub 80]Fe[sub 20] but not into Fe. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

HITPERM/SiO[SUB2] single and multilayer thin films have been produced using a target composition of Fe[SUB]70Co[SUB30])[SUB88]Zr[SUB7]B[SUB4]Cu[SUB1]. The as-deposited HITPERM film contains small bcc (or B2) nanocrystals of volume fraction less than 10% surrounded by an amorphous matrix. The lattice parameter of the nanocrystal is about 5% larger than an equilibrium FeCo phase. The saturation induction determined from FMR measurements (1.53±0.08 T) is consistent with VSM and SQUID measurements (1.45-1.5 T) and also with as-spun amorphous ribbons (1.55-1.62 T). The Landé g-factors (2.15±0.05) are typical of transition metals, particularly, of Fe. The Landau-Lifshitz-Gilbert damping parameters of the single and multilayered films are small (α=5 0.005±60.0004) with each layer acting almost independently. Neither thickness variation of each layer nor the number of stacking significantly affects the damping process in a range of film thicknesses of 50-150 nm, while the coercivities are strongly dependent on those parameters. This supports a notion that the damping parameter is an intrinsic property. [ABSTRACT FROM AUTHOR]

The magnetic domain structure, magnetic properties, and thermal stability of IrMn biased top spin valves containing Co and NiFe have been investigated. The magneto-optical indicator film pictures of Ni-Fe biased IrMn spin valve show the formation and motion of domain walls that separate large domains in the free film unlike the Co biased IrMn spin valve structure with many small microdomains. From the angular dependence of the ferromagnetic resonance linewidth (ΔH) and resonance field (H[sub res]) it was found that the IrMn biased Co film is very different from the behavior of a NiO biased Permalloy film which exhibits two-magnon scattering. To investigate the thermal stability two kinds of magnetoresistance measurements at anneal temperature (T [sub Anm]) and room temperature (T[sub RT]) following anneals were accomplished. [ABSTRACT FROM AUTHOR]

We present the dependence of the magnetostriction in Ni[sub 0.8]Fe[sub 0.2] films on Tb and Gd doping concentration and compare with the measured doping dependence of the high-frequency damping. While the magnetostriction and the high-frequency damping are correlated, the dependence is complicated. In particular, the high-frequency damping parameter α increases rapidly (α=0.008–0.84) with a modest increase in the magnetostriction (λ[sub s]=-0.6×10[sup -6] to 5.7×10[sup -6]) for Tb doping concentrations up to 10%. For Gd doping, the high-frequency damping changes slowly (α=0.008–0.02) as the doping concentration is increased to 10%, whereas the increase in magnetostriction is similar to that observed in the Tb-doped films. Further, it is possible to achieve low magnetostriction (λ[sub s]=2×10[sup -6]) near the region of critical damping. Measurements of the angular dependence of the ferromagnetic resonance linewidth in Tb-doped Ni[sub 0.8]Fe[sub 0.2] films show little change similar to the behavior observed in undoped Ni[sub 0.8]Fe[sub 0.2] films, although the linewidths are considerably larger. This is in contrast to systems such as Ni[sub 0.8]Fe[sub 0.2] on NiO, which have a large angular dependence indicating that the relaxation process proceeds through the generation of spin waves. The enhanced damping in the Tb-doped films appears, therefore, to be mediated through direct phonon generation. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

For a uniformly magnetized rectangular particle with dimensions in the ratio 5 : 1 : 0.1, the coercive and switching fields in the (1,1,1) direction are determined to be H[sub c]/M[sub s]=0.057069478 and H[sub s]/M[sub s]=0.057142805. Previous micromagnetic computations of coercive and switching fields that did not approach these values for small particles are analyzed. It is shown that the disagreement was primarily due to a disparity in the method of calculating demagnetization energy. Corrected simulations are shown to agree with analytically determined values. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report the frequency dependence of the ferromagnetic resonance linewidth of the free layer in magnetic tunnel junctions with all perpendicular-to-the-plane magnetized layers. While the magnetic-field-swept linewidth nominally shows a linear growth with frequency in agreement with Gilbert damping, an additional frequency- dependent linewidth broadening occurs that shows a strong asymmetry between the absorption spectra for increasing and decreasing external magnetic field. Inhomogeneous magnetic fields produced during reversal of the reference and pinned layer complex is demonstrated to be at the origin of the symmetry breaking and the linewidth enhancement. Consequentially, this linewidth enhancement provides indirect information on the magnetic coercivity of the reference and pinned layers. These results have important implications for the characterization of perpendicular magnetized magnetic random access memory bit cells. [ABSTRACT FROM AUTHOR]

Presents a study of the magnetization process of granular cobalt-silver films. Use of the magneto-optical indicator film technique and magnetic force microscopy in the study; Quality characterization of high-temperature superconductors; Analysis of magnetization domains.

Studies the magnetic properties of nanograin iron powder. Details on the experiment; Hysteresis loops of the powder samples; Information on the time effect phenomenon in multilayer systems.

Explores the sensitivity of the structural and magnetic properties to departures from stochiometry by focusing on a series of samples with fixed Hf:Ta concentration ratio. Lattice parameters determined from Rietveld refinements of x-ray powder diffraction data; Magnetization versus temperature curves measured in a maximum applied field of kOe; Determination of field-induced entropy change for the samples.

Part I. Presents a study that calculated the demagnetized state dependence of Henkel plots using the classical Preisach model. Description of the classical Preisach model; Models used to compute Henkel plots; Conclusions.

We report on the parametric excitation of magnetic precession modes in nanodisks using a parallel pumping configuration. The excitations are detected using a ferromagnetic resonance force microscopy method, and the parallel-pumped spectra reveal nonlinear characteristics including instability thresholds and multiple, narrow, sawtooth-shaped resonances. These characteristics are in accord with analytical theory and micromagnetic modeling results. Modeled mode profiles of the excitations show that higher-order standing spin-wave modes with both even and odd symmetries are excited under parallel pumping. [ABSTRACT FROM AUTHOR]

We report ferromagnetic resonance force microscopy of confined spin-wave modes with improved, 100 nm resolution. The ferromagnetic resonance spectra in Permalloy disks (diameters ranging from 100 to 750 nm) distinguish multiple edge modes, and the images reveal distinct precession patterns. The fundamental edge mode also provides a new, localized probe of the magnetic properties of the film edge; rotation of the applied field reveals large edge property variations in nominally circular disks. As a function of disk diameter, the number of observed edge modes agrees with modeling. [ABSTRACT FROM AUTHOR]

We introduce an implementation of magnetophoresis to measure the absolute magnetization of ferromagnetic nanorods dispersed in fluids, by analyzing the velocity of single nanorods under an applied magnetic field gradient. A microfluidic guideway prevents aggregation of nanorods, isolates them, and confines their motion for analysis. We use a three-dimensional imaging system to precisely track nanorod velocity and particle-surface proximity. We test the effect of the guideway on nanorod velocity under field gradient application, finding that it guides magnetophoresis, but imposes insignificant drag beyond that of a planar surface. This result provides insight into the transport of magnetic nanorods at microstructured interfaces and allows the use of an analytical model to accurately determine the reacted viscous drag in the force balance needed for quantitative magnetometry. We also estimate the confining potential of the guideway with Brownian motion measurements and Boltzmann statistics. We use our technique to measure the magnetization of ferromagnetic nanorods with a noise floor of 8.5 × 10-20 A·m2·Hz-½. Our technique is quantitative, rapid, and scalable for determining the absolute magnetization of ferromagnetic nanoparticles with high throughput. [ABSTRACT FROM AUTHOR]