Effect of planar anisotropy on damping decrement of free oscillations of magnetization in garnet-ferrite films

The results of experimental investigation of free oscillations of magnetization in garnet-ferrite films with planar anisotropy are considered. It is shown that the damping decrement of free oscillations increases with effective anisotropy field H _Kp .     

Phase-controlled force and magnetization oscillations in superconducting ballistic nanowires

The emergence of superconductivity-induced phase-controlled forces in the (10(-2)-10(-1)) nN range and of magnetization oscillations in nanowire junctions is discussed. A giant magnetic response to applied weak magnetic fields is predicted in the ballistic Josephson junction formed by a superconducting tip and a surface, bridged by a normal-metal nanowire where Andreev states form.     

Rabi-type oscillations in a classical Josephson junction

We study analytically and numerically the phase-modulation properties of a classical Josephson tunnel junction biased in the zero-voltage state and phase locked to an external ac field. We show that the phase-locked state is being modulated in the transients, or in response to perturbations, and the modulation frequency is calculated as a function of relevant system parameters, such as microwave field amplitude. Our analysis demonstrates that the modulation of a phase-locked state in an entirely classical Josephson junction produces oscillations analogous to quantum mechanical Rabi oscillations, expected to be observed under the same conditions.     

Micromagnetic simulation of magnetization reversal in controlled mesoscopic ferromagnetic junction

Magnetisation switching process and corresponding domain structures of mesoscopic ferromagnetic junction with different thickness are studied with micromagnetic simulation using Landau–Lifshiz–Gilbert equations. It is demonstrated by simulation results that the reversal process and switching field are dominated by the wide pad parts and only weakly depend on the wire parts.     

Magnetic field dependent magnetization oscillations in two-dimensional quantum electron systems

A simple relationship between amplitudes of magnetization oscillations is presented as result of a single-electron Josephson junction in a two-dimensional quantum electron system with a perpendicular magnetic field.     

Specific features of quantum oscillations of magnetization in quasi-two-dimensional antiferromagnetic semimetals

The specific features of quantum oscillations of the magnetization in quasi-two-dimensional wide-band-gap antiferromagnetic semimetals with a low concentration of charge carriers have been considered theoretically. It has been shown that, in these systems, the Fermi energy determined from the analysis of the frequency of the de Haas–van Alphen oscillations according to the standard procedure can differ significantly from the true value. For the correct determination of the Fermi energy in the canted phase, it has been proposed to analyze quantum oscillations of the magnetization M not as a function of the inverse magnetic field 1/H, but as a function of 1/cosγ, where the angle γ characterizes the inclination angle of the magnetic field with respect to the plane of the quasi-two-dimensional semimetal.     

Free magnetization oscillations in garnet ferrite films with quasi-planar anisotropy

Free magnetization oscillations in garnet ferrite films with quasi-planar anisotropy was studied. The oscillations were excited by a pulse of an in-plane magnetic field. An analytic expression relating the oscillation frequency to the film parameters and the external magnetic field was derived; the expression is in good agreement with the experimental data. The planar anisotropy is shown to increase the free-oscillation damping.     

Mesoscopic oscillations of the magnetization near Ising impurity centers in strong magnetic fields

The frequency of orientational quantum oscillations of the magnetization near impurity-ion clusters with Ising properties in a saturated magnetic crystal is calculated. It is noted that in compounds of the type Ho_xY_3−x Fe₅O₁₂, where magnetic phase transitions are observed, additional magnetization reversal and magnetic resonance features due to mesoscopic oscillations of the magnetization can be observed at low concentrations x<0.001 and cryogenic temperatures in fields comparable to the intersublattice exchange interaction field. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 6, 445–448 (25 March 1997)     

Effect of frustration on the magnetization in nickel ferrite-chromites

A study is reported on the behavior of the isotherms of the magnetization σ(H) and of the longitudinal λ_‖(H), transverse λ_⊥(H), volume ω(H), and anisotropic λ_t(H) magnetostrictions measured at T=80 K in the Cu_0.4Fe_0.6[Ni_0.6Cr_1.4]O₄ and Zn_0.4Fe_0.6[Ni_0.6Cr_1.4]O₄ ferrite-chromites having a frustrated magnetic structure. It has been established that these ferrite-chromites do not undergo technical magnetization and that the growth of the magnetization with the field is accounted for by two paraprocesses of different natures.     

Exchange interaction and oscillations of the magnetization of the electron gas in a quantum cylinder

The exchange energy of the electron gas on a cylindrical surface in a constant magnetic field has been calculated. Analytical formulas describing the contribution of the exchange interaction into oscillations of the magnetization of the electron gas in a quantum cylinder have been obtained. It is shown that the magnetic response of the system exhibits Aharonov-Bohm oscillations for both degenerate and Boltzmann electron gases.     

Quantum oscillations of resistance and magnetization in the degenerate semiconductor n-HgCr2Se4

In the magnetic field range ΔH=8–60 kOe we observed and studied the anomalous oscillations in the magnetic field dependence of the resistance and magnetization of single crystals of n-HgCr₂Se₄. The absence of periodicity in 1/H in the ΔH=8–20 kOe range can be explained by the non-Fermi-liquid behavior of the electron subsystem and agrees with the theory of the de Haas-van Alphen in systems with intermediate valence. In stronger fields, ΔH=20–60 kOe, the amplitude of the fundamental harmonic decreases, with the number and amplitude of the higher-order harmonics increasing. As a result, noise is superimposed on the signal as magnetic field strength grows. The temperature dependence of the magnetization is the sum of the monotonic spin-wave contribution and the oscillating part. Zh. éksp. Teor. Fiz. 113, 1877–1882 (May 1998)     

Effect of quantum entanglement on Aharonov-Bohm oscillations, spin-polarized transport and current magnification effect

We present a simple model of transmission across a metallic mesoscopic ring. In one of its arm an electron interacts with a single magnetic impurity via an exchange coupling. We show that entanglement between electron and spin impurity states leads to reduction of Aharonov-Bohm oscillations in the transmission coefficient. The spin-conductance is asymmetric in the flux reversal as opposed to the two-probe electrical conductance which is symmetric. In the same model, in contradiction to the naive expectation of a current magnification effect, we observe enhancement as well as suppression of this effect depending on the system parameters. The limitations of this model to the general notion of dephasing or decoherence in quantum systems are pointed out.     

Reduction in critical current density of current-induced magnetization switching

We have investigated the current-induced magnetization switching in an exchange-biased spin valve structure. By using an unpatterned antiferromagnetic layer to pin the fixed Co layer, we obtained a lower switching current density by a factor of 5 than a simple spin valve structure. For the application, it is important to know how to keep the spin polarization when the thicker layer is pinned by an antiferromagnet. The unpatterned pinned ferromagnetic lead can be a good solution for spin-transfer-torque-activated device. The effect of Cu buffer layer on the top of the thin Co and Ru buffer layer under the thick Co layer on the current-induced magnetization switching in cobalt-based trilayer spin valves was also investigated. The experimental results showed that the Ru buffer layer in combination with Cu buffer layer could induce a decrease in the critical switching current by 30%, and an increase in the absolute resistance change by 35%, which is caused by an improvement of a microstructure of a thicker Co polarizer.     

The effect of magnetic ordering on the quantum temperature oscillations of current-carrier magnetization in strongly correlated systems

We show that the effect of magnetic ordering in magnetic semiconductors by the mechanism of s-d(f) exchange interaction plays an important role in explaining the quantum temperature oscillations of band-electron magnetization that were discovered in the experiments of S. G. Ovchinnikov, V. K. Chernov, A. D. Balaev, N. B. Ivanova, B. P. Khrustalev, and V. A. Levshin (JETP Lett. 64, 642 (1995)). We analyze how hybridization of band and localized electrons affects the amplitude of this effect. Finally, we establish that because of strong intratomic correlations the amplitude of the oscillation effects depends to a great extent on the sign of the exchange constant J. Zh. éksp. Teor. Fiz. 111, 654–668 (February 1997)     

Unidirectional anisotropy and the roughness of the ferromagnet-antiferromagnet interface

Magnetization curves of a ferromagnetic film on an antiferromagnetic substrate are investigated with allowance for the frustration caused by roughness of the interface. The conditions for unidirectional anisotropy are determined, and its dependence on the degree of roughness of the film-substrate interface is found.     

Modeling magnetization oscillations in ferromagnetic cobalt disks exposed to picosecond laser pulses

Magnetic reversal of a ferromagnetic single-domain nanoparticle in the form of a disk contained in a multilayer nanostructure irradiated by linearly and circularly polarized picosecond laser pulses is modeled. It is shown that heating of the disk by the laser light causes a change in its direction of magnetization. This is accompanied by oscillations in the magnetization that decay over 1–16 ns. The frequencies of these oscillations lie in the range of 0.5–26 GHz. The main reason for the magnetic reversal of the disk is a change in the magnetic anisotropy energy during heating. The laser pulses also create a spin-polarized current and an inverse Faraday magneto-optical field in the structure, which influence the duration, amplitude, and frequency of the magnetization oscillations.     

Impurity-induced coherent current oscillations in one-dimensional conductors

The electronic transport through a single impurity in a repulsive Luttinger liquid (LL) has been theoretically studied. It has been found that the direct current Ī above the threshold voltage related to the strength of the impurity potential is accompanied by coherent oscillations with frequency f= Ī/e. There is an analogy with the Josephson junctions: the well-known regime of the power-law I−V curves in the LL corresponds to the damping of the Josephson current below the critical one, while the oscillatory regime in the LL can be compared with the Josephson oscillations above the critical current. The text was submitted by the authors in English.