Evidence for an antiferromagnetic component in the magnetic structure of ZrZn2

Zero-field muon spin rotation experiments provide evidence for an antiferromagnetic component in the magnetic structure of the intermetallic ZrZn₂.     

Relationships between the magnetic structure parity of an easy-axis antiferromagnet and the refraction mode of electromagnetic waves of the TM and TE types

The role of antisymmetry in the refraction processes of electromagnetic waves of the TM and TE type that recede from nonmagnetic media at an arbitrary angle on the surface of a compensated antiferromagnet for a longitudinal magnetooptical configuration is examined.     

Effect of roughness on the magnetic structure of ferro/antiferromagnetic interface

Spin structures at the ferro/antiferromagnetic interfaces perturbed by defects such as atomic high steps are analytically investigated. A two-dimensional model is proposed to describe the spin distribution formed on the interfacial step at the domain wall. A criterion of the domain wall configuration relative to the interface is found, defined by the magnetic and geometrical characteristics of the interface and the magnet.     

Distortions of the magnetic structure of a thin antiferromagnetic layer in magnetic field

Distortions induced by an external magnetic field in the magnetic structure of a thin layer of a uniaxial collinear antiferromagnet with rough surfaces are studied using computer simulation. It is shown that, under certain conditions, the presence of atomic steps at the layer surfaces causes the antiferromagnetic layer to break up into domains. The character and magnitude of distortions are found for an arbitrary ratio of the distance between atomic steps to the order parameter correlation length. Original Russian Text ? A.I. Morosov, I.A. Morosov, A.S. Sigov, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 7, pp. 1228–1235.     

Reflection of electromagnetic waves from the layered structure of a high-temperature superconductor-multiferroic with cycloidal antiferromagnetic structure

The reflection of electromagnetic waves from the layered structure of a high-temperature superconductor-multiferroic with cycloidal antiferromagnetic structure in an external magnetic field is studied. The frequency dependence of the reflection coefficient at different values of an external magnetic field is calculated. The possibility of effectively controlling the reflective properties of the structure is established.     

Self-induced transparency and electromagnetic pulse compression in a plasma or an electron beam under cyclotron resonance conditions

Based on analogy to the well-known process of the self-induced transparency of an optical pulse propagating through a passive two-level medium we describe similar effects for a microwave pulse interacting with a cold plasma or rectilinear electron beam under cyclotron resonance condition. It is shown that with increasing amplitude and duration of an incident pulse the linear cyclotron absorption is replaced by the self-induced transparency when the pulse propagates without damping. In fact, the initial pulse decomposes to one or several solitons with amplitude and duration defined by its velocity. In a certain parameter range, the single soliton formation is accompanied by significant compression of the initial electromagnetic pulse. We suggest using the effect of self-compression for producing multigigawatt picosecond microwave pulses.     

Controlling the speed of electromagnetic waves in TbMnO3 in the sinusoidal antiferromagnetic phase by means of an external magnetic field

The possibility of controlling the speed of electromagnetic waves in TbMnO₃ of sinusoidal electromagnetic structure is investigated. Expressions for the components of the susceptibility tensors are obtained. Frequency dependences of the speed of electromagnetic waves are calculated for different values of an external magnetic field.     

Modulation in the statistical properties of stochastic electromagnetic beams through an electromagnetic induced transparency atomic vapor

We report analytical expressions for the elements of the 2 × 2 cross-spectral density matrix of a stochastic electromagnetic beam passing through an electromagnetic induced transparency (EIT) atomic vapor. By use of the derived formulas the changes in the spectral density, the spectral degree of coherence, and the spectral degree of polarization of such a beam on propagation can be studied in detail. Numerical examples show that the statistical properties of the stochastic electromagnetic beam can be modulated by the Rabi frequency of the control light when the beam propagates through the EIT atomic vapor.     

Influence of the soliton-magnon interferences on the dynamics of an antiferromagnetic chain

We study the influence of small amplitude fluctuations on the soliton induced dynamic structure factors of the classical one dimensional antiferromagnet with two single ion anisotropies. In contrast to the case of an external magnetic field the equations of motion for the in-plane and out-of-plane fluctuations separate and can be solved exactly.     

Reflecting electromagnetic waves from a surface of TbMnO3 with sinusoidal antiferromagnetic structure

A spectrum of coupled waves in TbMnO₃ with sinusoidal antiferromagnetic structure is investigated. Expressions for the activation frequencies are obtained, and temporal and spatial permittivity dispersions are considered. Frequency dependences for the reflectance of electromagnetic waves from the TbMnO₃ surface are calculated.     

电磁诱导透明的经典类比

介绍了电磁诱导透明现象及实质,并利用2个经典的线性耦合RLC电路模拟演示了电磁诱导透明现象,发现耦合电容越小,效果越明显.该实验有益于学生对量子相干现象的理解.     

Spiraling spin structure in an exchange-coupled antiferromagnetic layer

Using trilayers of permalloy/FeMn/Co with various thicknesses t(AF) of the antiferromagnetic FeMn, we have observed evidence of a spiraling spin structure within FeMn. For t(AF)<90 A, the turn angle straight theta of the spiral varies as straight theta = (1.76 degrees /A)t(AF).     

Anomalous penetration of an electromagnetic signal in a thin metallic plate under strong magnetodynamic nonlinearity conditions

A new phenomenon of anomalous transparency of a metallic plate upon the passage of a strong transport current is predicted. It is shown that the electromagnetic field of an incident wave may be carried from the skin layer to the opposite face by electrons trapped by the alternating intrinsic magnetic field of the transport current even under the conditions of the extremely anomalous skin effect for which the skin depth is the smallest parameter having the dimensions of length. The mechanism of the rf field transport effectively operates at low temperature, when the mean free path of charge carriers is large. The wave field distribution in the plate is analyzed. The cyclotron resonance at trapped electrons, which emerges due to their periodic return to the skin layer, is predicted and qualitatively analyzed.     

The influence of hexagonal anisotropy on the magnetic structure of antiferromagnetic rare earth metals and alloys

The effect of hexagonal base plane anisotropy on the antiferroniagnetic (AF) spiral spin structure of rare earth metals and alloys has been investigated. Minimization of the anisotropy energy is considered either by a reorientation of rigid coherent sections of the spiral or by a continuous modulation of the spiral periodicity. Both results indicate that when the spiral periodicity is commensurate with the hexagonal anisotropy the energy is greater than for spirals which are non-commensurate. The calculations predict that when the temperature is varied in the AF phase, the magnetic structure becomes unstable as a commensurate turn angle is approached, which may provide a qualitative explanation for the abrupt changes in the c-axis thermal expansion and temperature dependence of the elastic constant C₄₄ that have been observed experimentally in dysprosium and terbium-50% holmium. Further consequences of the spiral perturbation by hexagonal anisotropy are considered.     

外磁场中海森伯反铁磁模型的代数结构和压缩态解

外磁场中的XYZ海森伯反铁磁模型，其哈密顿量在自旋波近似下具有so(3,2)李代数结构. 利用代数对角化方法，可得到压缩态形式的能量本征态和相应的能量本征值. 用此方法进一步讨论本征态的基本性质，并建立反铁磁模型与特定类型的双模耦合谐振子的联系. 关键词： 海森伯反铁磁模型 代数对角化 压缩态     

Influence of amorphous environment on magnetic structure

The influence of disordered medium on the magnetic structure of crystalline clusters is discussed. In a plate-like crystalline cluster with localized moments the disordered magnetic environment leads to preference of a spiral magnetic structure over the antiferromagnetic collinear ordering that would be otherwise realized. By the numerical solution of a specific model qualitative information was obtained about the influence of the exponential rate of decrease of the exchange interaction, plate thickness and degree of disorder of the medium on the magnetic structure of the cluster.     

Spin flop transition in a finite antiferromagnetic superlattice: evolution of the magnetic structure

An antiferromagnetic (AF) superlattice of Fe/Cr(211) is used as a model system to study magnetic transitions in a finite-size geometry. With polarization neutron reflectometry the magnetic structure at the surface spin-flop transition and its evolution with field is determined. A domain wall created near the surface penetrates the superlattice with increasing field, splitting it into two antiphase, AF domains. After reaching the center the spin-flopped phase spreads throughout the superlattice. The experimental results are in substantial agreement with theoretical and numerical predictions.     

Nonresonant transparency channels of a two-barrier nanosystem in an electromagnetic field with an arbitrary strength

The theory of the quasistationary spectrum of the system of electrons interacting with a high-frequency electromagnetic field with an arbitrary strength in a two-barrier resonant tunneling nanostructure has been proposed on the basis of the exact solution of the total one-dimensional Schrödinger equation. It has been shown that nonresonant transparency channels in the planar two-barrier resonant tunneling structure appear owing to the superposition of a certain quasistationary state with first field resonance harmonics of both nearest states; this superposition is due to the interaction of electrons with the electromagnetic field.     

On the nonlinear dynamics of the easy-plane antiferromagnetic chain in an external magnetic field

We present a theoretical investigation of soliton excitations in an easy-plane 1d antiferromagnet in an external magnetic field beyond the Sine-Gordon approximation. We find that there exist two types of solitons. One of them depends strongly on the magnetic field, becoming unstable at a critical magnetic field B_c. The other one is stable for all magnetic fields and can be described by a Sine-Gordon model. We discuss the relevance of these excitations for neutron scattering experiments.     

Magnetic phase diagram of the spin-valve structure with an antiferromagnetic oxide layer

The magnetic phase diagram of a three-layer ferromagnet-antiferromagnet-ferromagnet structure with an antiferromagnetic oxide layer of variable thickness has been investigated. It has been predicted that there are three ranges of thicknesses in which domain walls created by the frustration of the exchange interaction between the layers have different structures. The structure of these domain walls induced by edges of atomic steps at the interfaces between the layers has been described. The predictions of the theory have been compared with the available experimental results, in particular, with the data indicating the existence of the nanodomain state.