High-amplitude precession and dynamic unsusceptibility of magnetic moments of a two-layer film

The precession motion of magnetization in a longitudinal alternating magnetic field for a system of two antiferromagnetically coupled magnetoactive layers is studied. New dynamic modes characterized by large precession amplitudes and doubling of the period are found. The modes can be efficiently controlled using an external magnetic bias field. A new effect consisting in the unsusceptibility of a magnetic subsystem to excitation by an alternating field has been revealed.     

Spin precession waves in superfluid 3He-B

Spin precession waves of homogeneously precessing domains (HPD) in superfluid 3He-B have been studied at 11 bars and temperatures down to 0.45T(c). The waves were excited by an alternating longitudinal magnetic field with an axial symmetry, applied as a small perturbation ranging from 1 nT up to a few micro T. When the spin precession wave is excited, two nuclear magnetic resonances simultaneously coexist: first, the high frequency resonance used for excitation of the HPD, and, second, the low-frequency resonance of the HPD wave mode. We report the first experimental evidence of the nonlinear behavior of low-frequency precession spin wave modes of the continuously maintained HPD.     

On the nuclear magnetoelectric resonance in tetragonal KNbO3

The magnetic response of a KNbO₃ crystal due to the nuclear spin precession resulting from the excitation of nuclear spins by an alternating electric field has been investigated theoretically. The converse effect, i.e., the emergence of an alternating electrical polarization as a result of the magnetic excitation of nuclear spins, has also been considered.     

Frequency （Stochastic） Resonance and Stochastic Resonance for a Superconducting Junctions＇ Device

In this paper, we investigate a Josephson-junction device with dichotomous resistance or a special SQUID （superconducting quantum interference device）. It is shown that frequency （stochastic） resonance and stochastic reso- nance can appear for some suitably selected parameters＇ values of the device respectively. Our results can provide some insights for the investigation of the SQUID response to the signal （including the input alternating current, the added al- ternating voltage, the vertically added alternating magnetic field, and the detected （electric-magnetic） temporal-periodic signal）.     

Average transient period for precession regimes in magnetic films with dynamic bistability

The average transient time of regular regimes corresponding to the dynamic bistability state is studied using analysis of uniform precession of magnetization of a thin magnetic film. The possibility of controlling the transient process parameter by an additional ac magnetic field in the form of a harmonic of noise signal is established. A new type of stochastic resonance is detected, which corresponds to the probability of high-amplitude precession and is manifested during a short noise action.     

Switching of precession regimes under the conditions of dynamic bistability of magnetization

The dynamics of the magnetization of a single-crystal film under the conditions of dynamic bistability has been investigated using numerical simulation. It has been shown that the use of an additional alternating magnetic field has made it possible to suppress the dynamic bistability of magnetization and to implement one of the two precession regimes depending on the field frequency. Multiple switching between magnetization precessions with different amplitudes can be performed directly from one regime to the other regime due to the corresponding change in the frequency of the additional magnetic field.     

Spin-torque ferromagnetic resonance induced by the spin Hall effect

We demonstrate that the spin Hall effect in a thin film with strong spin-orbit scattering can excite magnetic precession in an adjacent ferromagnetic film. The flow of alternating current through a Pt/NiFe bilayer generates an oscillating transverse spin current in the Pt, and the resultant transfer of spin angular momentum to the NiFe induces ferromagnetic resonance dynamics. The Oersted field from the current also generates a ferromagnetic resonance signal but with a different symmetry. The ratio of these two signals allows a quantitative determination of the spin current and the spin Hall angle.     

Bifurcation magnetic resonance in type (100) films upon in-plane magnetization

The magnetization dynamics in (100) single-crystal films with a cubic anisotropy has been studied by numerical simulation. It has been shown that the additional (bifurcation) resonance caused by the bistability, i.e., two closely spaced equilibrium magnetization states, appears upon in-plane magnetization along the hard axis. The change in the resonance region and the corresponding dynamic regimes with a variation in the RF field or with a small detuning of the magnetizing field has been investigated. The regular and chaotic precession regimes near the bifurcation resonance have been revealed. The states of dynamic bistability have been found.     

Some principles in choosing parameters of magnetic resonance tomographs

The problem of amplifying the signal that ensures the visualization of internal organs in the magnetic resonance tomograph due to the optimal selection of some of its parameters has been considered. The operating principle of the tomograph has been analyzed. The relation between the angle of the magnetic moment precession in hydrogen nuclei in an organism, the frequency of the ac magnetic field exciting this precession, and the constant magnetic field used has been determined using quantum-mechanical concepts. This relation makes it possible to determine the optimal parameters for tomograph operation.

     

The effects of large oscillating fields on spin precession in magnetic resonance

Magnetic resonance of a spin system which is acted upon by a large near-resonance oscillating magnetic field transverse to a static field has been studied experimentally and theoretically for many years. The technique of DEMUR (Double Electron Muon Resonance) has many advantages for such studies. This paper will describe the results of an experiment to study the precession of the muonium triplet near magnetic resonance using DEMUR.     

Specific features in precession dynamics of magnetization of a uniaxial magnetic film

The precession dynamics of the magnetization of a film with in-plane uniaxial anisotropy in the case of its biasing along the hard magnetization axis has been analyzed by numerically solving the Landau-Lifshitz equations. It has been revealed that the ferromagnetic resonance spectrum near the magnetic anisotropy field exhibits an additional peak, which is associated with the angular bistability due to the presence of two symmetric angular equilibrium positions. The trajectories of precession motion during biasing along the hard magnetization axis differ substantially from the trajectories corresponding to the biasing along the easy axis.     

Nonlinear dynamic magnetization regimes in (100) ferrite-garnet films

To study the nonlinear dynamics of a uniformly precessing magnetization in perpendicularly magnetized (100) ferrite-garnet films, equations of motion are numerically solved over a wide ac field frequency range. Bifurcation changes in the magnetization precession and the states of dynamic bistability have been detected. The conditions of high-amplitude regular and stochastic dynamic regimes are revealed, and the possibilities of controlling these precession regimes by applied magnetic fields are shown.     

Stochastic resonance in single-domain nanoparticles with cubic anisotropy

The signal-to-noise ratio for magnetic stochastic resonance in a superparamagnetic particle with cubic anisotropy is shown to be strongly dependent on the Larmor precession damping α. This phenomenon is due to the coupling of the relaxation and precession modes and can be used for measuring α. The dependence of the signal-to-noise ratio on α is characteristic of particles with nonaxial anisotropy; so the effect is absent in uniaxial particles.     

Ferrimagnetische Resonanz in Rotationsellipsoiden

Ferrimagnetic resonance at 9660 Mc/s in prolate spheroids (ratio of axes 1:5 to 1:1) of polycristalline ferrites has been investigated. The saturation magnetization between room temperature and the Curie point has been calculated from the displacement of the field needed for resonance in comparison to spherical samples. The halfwidth depends strongly on the ratio of axes and the orientation of the samples because the uniform precession is displaced in relation to the upper spin wave limit.     

Nonlinear effects of magnetization precession near ferromagnetic resonance

The features of precession of the magnetic moment of a film near ferromagnetic resonance are investigated which are due to the magnetic-moment nutation in the effective field and to the frequency-doubling effect. The contribution to this precession from harmonics with frequencies which are multiples of the basic resonance frequency is analyzed for a garnet ferrite film of the (111) type in a perpendicular bias magnetic field.     

Präzession magnetischer Momente angeregter Atomzustände im äußeren Magnetfeld

The magnetic momentum of the 6³ P ₁ state of Hg 202 has been oriented by exciting mercury-202-vapour with the circularpolarized 2537 Å resonance line. The precession of the resulting magnetization around an external magnetic field has been studied by the observation of the linear and especially the circular degrees of polarization of resonance radiation. These measurements are interpreted by a simple rotator model.     

Dynamics of a magnetic moment of finite dipolar lattices in the AC field

Dynamic regimes of a magnetic moment of 2 × 2, 3 × 3, and 4 × 4 square dipole lattices in the linearly and circularly polarized ac magnetic field and the perpendicular static field have been investigated. The possibility of regular and chaotic precession dynamics of the magnetic moment of the lattices has been demonstrated. A shift of the main magnetic resonance owing to the dipole–dipole interaction and additional resonances have been revealed. Quasiperiodic regimes and bistability states with a metastable chaotic attractor have been discovered.     

Regular and chaotic precession of magnetization in magnetic films with a stripe domain structure

Based on a numerical solution of the equations of motion found over a wide range of frequencies of an alternating magnetic field, the nonlinear precession dynamics of magnetization are studied in thin-film structures of the (100) type with a stripe domain structure in a perpendicular bias field. The conditions are determined under which high-amplitude regular and chaotic dynamic regimes occur. Bifurcational variations in the precession of coupled magnetic moments and dynamic-bistability states are detected. The specific features of the spectrum of Lyapunov exponents and of time analogs of Poincaré cross sections of trajectories in chaotic regimes are considered.     

Natural ferromagnetic resonance in the disordered alloy Pd2AuFe

A contribution to electromagnetic power losses, additional to the losses due to eddy currents and exhibiting a resonance frequency dependence with the main maximum near 1 GHz, has been observed for the ferromagnetic alloy Pd₂AuFe in the frequency range 0.9 MHz–10 GHz in the absence of an external constant magnetic field. Investigations performed in a dc magnetic field show that this effect is a natural ferromagnetic resonance due to intradomain magnetization precession in the effective magnetic-anisotropy field. Fiz. Tverd. Tela (St. Petersburg) 40, 1900–1904 (October 1998)     

Muon spin resonance by strong pulsed r.f. field with pulsed muons

Muon spin resonance experiments have been performed for the ⁺ in H₂O and for some other cases, and the first observation has been made of the time-differential pattern of muon spin resonance, namely, spin precession around the r.f. field vector under various resonance conditions. In the present experiment, a high-power pulsed r.f. field was effectively applied to the pulsed muon beam in our laboratory of the KEK-Booster Meson Facility (BOOM). Potential uses of muon spin resonance, particularly for research in the border regions of solid state and nuclear physics, are discussed in comparison with the conventional spin rotation method.