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Magnetic resonance force microscopy measurements of the electron spin resonance of a thin film of 2,2-diphenyl-1-picrylhydrazyl were performed using a low doped silicon cantilever with a high coercivity SmCo particle glued to its end. The low doping level enables amplitude modulation of the microwave field with only small spurious driving of the cantilever. Besides amplitude modulation we use frequency modulation of the microwave field at integer fractions of the cantilever resonance frequency leading to derivative signals up to the fourth derivative of the amplitude modulation response signal. The influence of the modulation depth on the line shape of the first derivative response is also presented. [ABSTRACT FROM AUTHOR]

Magnetic and structural characteristics of ErFeO3, TmFeO3, and YbFeO3 single crystals were studied over a wide temperature range. Magnetic measurements found that the spin-rotation transitions in all crystals are well described by the earlier proposed theory with no fitting parameters. Additionally, they have shown the absence of the magnetic compensation point in TmFeO3 and a noticeable growth of the c-axis magnetization at low temperatures in TmFeO3 and ErFeO3. The x-ray measurements found no symmetry-lowering lattice distortions during the reorientation. Overall, the measurements cover a wide range of material parameters and demonstrate the generality of the modified mean field theory of the Γ4→Γ24→Γ2 orientation phase transitions in orthoferrites. [ABSTRACT FROM AUTHOR]

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.

The anomalous concentration dependence of the effective internal field in FeCo-[Al.sub.2][O.sub.3] granular films is explained in terms of local structure inhomogeneities. Using AFM, SQUID and FMR data it has been deduced that the composition of local film regions differs from the nominal one determined by EDAX. Index Terms--Ferromagnetic resonance, granular cermet films, SQUID magnetometer.

The granular layered magnetic system [Co.sub.80][Fe.sub.20] (t)/[Al.sub.2][O.sub.3] (3 nm), where the [Co.sub.80][Fe.sub.20] layers of nominal thickness t form separate, almost spherical magnetic granules of typical diameter 2-3 nm between the [Al.sub.2][O.sub.3] spacers, was studied. We discuss measurements of the dc and ac magnetic susceptibility [Chi] for 1 nm [is less than] t [is less than] 1.3 nm at temperatures 10 K [is less than] T [is less than] 300 K and ac frequencies 0.01 Hz [is less than] f [is less than] [10.sup.3] Hz, revealing a rich variety of magnetic states, including superparamagnetic (SPM), ferromagnetic (FM)-like, and glass (G)-like. In order to describe the ac response in this disordered planar system, a generalization of the Neel-Brown approach is proposed, including random anisotropy and random molecular fields acting on the granules. The observed magnetic states are summarized in a phase diagram in the variables t - T, which is explained through the competition of thermal energy with two kinds of interaction between granules: usual dipolar (point-like) and FM 'exchange' (due to stray dipolar fields from nonspherical granules). In particular, the coincidence of maximum low field sensitivity dMR/dH with the SPM-FM transition line on this diagram is confirmed. Index Terms--Discontinuous metal-insulator films, ferromagnetic transition, magnetic phase diagram, spin-glass transition.

Using the ferromagnetic resonance (FMR) technique, the interlayer coupling is studied in granular multilayered system (CoFe/Al2O3)n with varying number of layers n=1, . . . ,8. The main difference between the cases of n=1 and n⩾3 is a notable splitting of FMR line under external field normal to layers. This is explained by an interlayer dipolar coupling, only possible for discontinuous layers. The relative magnitudes of two absorption peaks and distance between them are described by a simple model of planar square lattices of magnetic dipoles. [ABSTRACT FROM AUTHOR]

Magnetization of ErFeO3 single crystal was measured by a super conducting quantum interference device magnetometer with greatly improved precision. A dramatic (70%) increase of magnetization was observed in the spin-reorientation interval (88–97 K). This and the temperature dependence of the spin-rotation angle are accurately described by the modified mean field theory, which uses the key fact of the magnetic anisotropy of erbium subsystem. Calculated temperature dependence of the rotation angle shows a remarkable correspondence with the experiment with no fitting parameters. Proposed model is general and can be used to analyze orientation transitions in many orthoferrites. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ferromagnetic resonance at 9.2 GHz (X band) was used to characterize the uniaxial magnetic anisotropies in rectangular arrays of submicron circular Ni dots. The in-plane anisotropy, originated from interdot interactions in the rectangular lattice, and the perpendicular anisotropy, due to individual dot shape and magnetostriction, were explored. For in-plane dependencies of the resonance field (H[SUBr]), the main resonance mode angular dependence was well described by the standard Kittel formula. As the interdot distances decreased from 800 to 50 nm, the in-plane uniaxial anisotropy field changed from 5 to 130 Oe, in reasonable agreement with calculations. Simultaneously, the position of perpendicular (H[SUBr]) increased from 6.38 to 6.83 kOe, also following) Kittel's formula. [ABSTRACT FROM AUTHOR]

We demonstrate spatial resolution of ferromagnetic resonance in a microscopic sample of YIG using ferromagnetic resonance force microscopy (FMRFM). Measurements were performed on a small single crystal YIG film grown on a GGG substrate, roughly rectangular in shape 20 μm×∼150 μm and 3 μm thick. The perpendicular and parallel force geometries of FMRFM, in conjunction with an external bias field both parallel and perpendicular to the film, were used to scan the sample. This enabled the detection of strong signals, even at atmospheric pressure and room temperature. The fundamental and higher-order magnetostatic modes were observed to have 26–29 Gauss separation. The intensity of these modes exhibited spatial variation as the magnetic tip was scanned over the sample, and this behavior is qualitatively explained by DE theory. An improved fabrication method for magnet on cantilever was employed, which yielded a spatial resolution of 15 μm. These results demonstrate the potential of FMRFM for investigating the spatial dependence of ferromagnetic resonance, and for studying the anisotropy fields and exchange coupling effects within multilayer films and small magnetic systems. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the bifurcation to chaos in auto-oscillations in circular yttrium-ion garnet films. Time dependence of the complex Lyapunov exponent; Bifurcation diagram; Control and robustness analysis.

Details a study which investigated the Faraday rotation of bismuth and thulium substituted yttrium iron garnet films. Theoretical model for the temperature dependence of Faraday rotation; Experimental procedures; Influence of bismuth ion on electronic behavior of tetrahedral sublattice iron ions.

Presents a study which investigated the domain wall oscillations of parallel stripe domains in the thin films of substituted yttrium-iron garnet. Calculation of the resonance frequencies and wall profiles for different flexural modes; Discussion on the dynamics of a continuous magnetic medium; Illustration of experimentally observed frequencies for different modes as a function of in-plane field.

Discusses the resonance condition of a bilayer antiparallel coupled magnetic layer system with the magnetic field along both the parallel and perpendicular directions. Regions that exist when the external field in the film plane is parallel to the in-plane easy axis; Function of ferromagnetic resonance; Coupling strength between magnetic layers.

Presents a study which investigated the magnetic properties of direct current sputtered cobalt/platinum multilayer films using ferromagnetic resonance and vibrating sample magnetometer. Experimental details; Results and discussion; Conclusion.

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.

Focuses on a study which measured the temperature and time dependence of the initial susceptibility of the optical magnetization curve on epitaxial films of nominally pure yttrium iron garnet during illumination with white light after cooling in the dark. Maximum temperature for the occurrence of the light-induced effects on the susceptibility; Process of the change to low-susceptibility state by light excitation; Interpretation of results.

Presents a study which examined chaos in magnetic garnet thin films. Experimental details; Results and discussion; Description of the model.

Presents a study that analyzed an expression for the superexchange coupling between spins of localized electrons by using a periodic Anderson model with intersite hybridization. Equations used in the hybridization; Effect of calcium&sup2+; doping on the magnetic superexchange coupling between ions spins.

Presents information on a study which measured the equilibrium optical absorption and the near steady state photoinduced absorption on charge-uncompensated calcium-doped yttrium iron garnet epitaxial thin films. Compensation by electron holes localized on the oxygen ions; Concept of the photoinduced absorption technique; Normal optical absorption spectra of the samples.

Presents a study that measured the magnetic full linewidth of yttrium iron garnet films. Methodology; Correlation between linewidth measurements and the temperature; Examination of the frequency dependence of the linewidth measurements.

Examines the effects of simultaneous substitution of calcium&sup2+; and scandium[3+] on the magnetic properties of yttrium iron garnet (YIG). Measurement of the temperature dependence of the magnetization; Predictions for the composition dependence of the Curie point for octahedrally substituted YIG.

Focuses on a study which measured the temperature dependence of the magnetization of epitaxial films of yttrium calcium iron garnet system. Materials and experimental procedure; Results of molecular field calculations; Comparison between the calculations and the experimental results.

Presents information on a study which investigated the formation of the high conduction state in garnet films. Methodology of the study; Results and discussion.

Focuses on a study which examined the temperature dependence of the anomalous g value of bismuth thulium: yttrium iron garnet. Theory for the effective g value; Experimental procedures; Determination of sublattice magnetization; Conclusion.

Focuses on a study that proposed a theoretical model to explain the magnetic properties of uncompensated CaGe:yttrium-iron garnet with excess calcium. Magnetization; Single ion cubic anisotropy of Fe{sup 4+] ion in yttrium-iron garnet; Conclusions.

Presents information on a study which described the excitation effects of light and electric field on the electrical transport properties of CaGe:yttrium iron garnet epitaxial films. Room temperature-conductivity of the films; Method for increasing low-temperature conductivity of the films; Excitation of the high-conductivity state.

Presents a study which measured ferromagnetic resonance (FMR) spectra in reduced calcium-rich CaGe:YIG film. Analysis of ferromagnetic resonance measurements; Effect of reducing time on the room-temperature FMR spectra of an epitaxial CaGe:YIG crystal.

Provides information on a study that observed interactions between the domain wall resonance mode and the domain ferromagnetic resonance modes for the first time in unsaturated gallium- and lanthanum-doped thin yttrium iron garnet films. Experimental observations; Results and discussion on the study; Conclusion.