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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]

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]

Due to the finite aspect ratio of the ferrite, the distribution of the internal field in small planar microwave ferrite devices is strongly inhomogeneous. This is a source of additional losses through magnetostatic modes. To study the magnetostatic modes, the thickness dependence of the ferromagnetic resonance spectra was measured for a series of 2 mm square single crystal yttrium–iron–garnet films in the 35

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]

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.

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.

Focuses on a study on giant magnetoresistance peaks in CoNiCu/Cu multilayers grown by electrodeposition. Introduction to giant magnetoresistance; Experimental details; Analysis of the high angle x-ray diffraction patterns.

Deals with a study which assessed the magnetocaloric properties of Gd[subx]Ag[100-x] alloys prepared through melt spinning. Information on field-induced entropy change of a magnetic material; Preparation of alloy ingots; Examination of ribbon microstructures.

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.

Examines the effect of twin boundaries on flux pinning in yttrium-barium-copper oxide at low and intermediate magnetic fields. Description of crystals used in the study; Use of a commercial superconducting quantum interference device in measuring the magnetic properties of the crystals; Experimental details and result of the study.