Intermixing during epitaxial growth and Mössbauer spectroscopy with probe layers

Mössbauer spectroscopy with ⁵⁷Fe (¹¹⁹Sn) probe layers is a useful method to study the local magnetic structures at buried interfaces. However interface alloying, which always exists in the real samples, have to be taken into account for accurate interpretation of experimental data. We developed an algorithm, which describes the interface intermixing in the multilayers. Substituting deposited atoms by atoms of substrate and floating of deposited atoms in the upper layers during epitaxial growth leads to the formation of asymmetric chemical and magnetic interfaces. This asymmetry in the M₁/M₂ superlattices can explain the difference between magnetic responses from M₁ on M₂ and M₂ on M₁ interfaces which were observed in experiments. Applying this intermixing model to the systems with probe layers located at different distances from the interfaces gives the natural explanation of hyperfine fields distributions on probe atoms and helps us clarify some discrepancies reported in the literature.     

Collisions between optical spatial solitons propagating in opposite directions

We formulate the theory describing the evolution and interactions between optical spatial solitons that propagate in opposite directions. We show that coherent collisions between counterpropagating solitons give rise to a new focusing mechanism resulting from the interference between the beams, and that interactions between such solitons are insensitive to the relative phase between the beams.     

Collisions between (2+1)D rotating propeller solitons

We study theoretically the collisions between (2+1)D rotating-dipole-type bimodal solitons and find that such interactions exhibit many interesting exchanges of angular momentum.     

Rotating propeller solitons

We demonstrate experimentally and theoretically (both analytically and numerically) a new type of spatial soliton: a rotating "propeller" soliton. This is a composite soliton made of a rotating dipole component jointly trapped with a bell-shaped component. We observe as much as 239 degrees of rotation over 13 mm of propagation (6.5 diffraction lengths).     

Random replicators with high-order interactions

We use tools of the equilibrium statistical mechanics of disordered systems to study analytically the statistical properties of an ecosystem composed of N species interacting via random mutual interactions, as well as via deterministic self-interactions of order p>/=2. We show that the main effect of increasing the order of the interactions among the species is to make the system less competitive, in the sense that the fraction of extinct species is greatly reduced. In addition, we find that for p>2 there is a threshold value which gives a lower bound to the concentration of the surviving species, preventing then the existence of rare species and, consequently, increasing the robustness of the ecosystem to external perturbations.     

Investigating phase transitions in a model Fe/V magnetic superlattice

We propose a model of an iron-vanadium superlattice for investigating phase transitions in multilayers. Several basic types of temperature dependences of spontaneous (resultant) magnetization in a magnetic superlattice model are revealed for the first time for various values of an interlayer exchange interaction.     

Features of the magnetic state of the layered Fe-V nanostructure of the superconductor-ferromagnet type

The magnetic state of the V(39 nm)/20 [V(3 nm)/Fe(3 nm)] nanostructure has been investigated by polarized neutron reflectometry in the temperature range from 1.6 to 30 K in magnetic fields from 0.2 to 15 kOe. The data obtained indicate that the superconductivity of vanadium layers may affect magnetic ordering both over the depth of the structure and in its plane.     

On the calculation of the magnetic structure of surfaces,near-surface layers,and interfaces of 3d metals

Physics of the Solid State - A microscopic approach to the calculation of the distribution of magnetic moments in the vicinity of surfaces, interfaces, and other spatially inhomogeneous 3d metal...     

Spectral representation of nonequilibrium Green's functions in the Kadanoff-Baym technique

A. I. Gertsen State Pedagogical Institute, Leningrad. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 84, No. 1, pp. 141–145, July, 1990.     

Response of Mn overlayers on Fe to external magnetic fields: Electronic structure calculations

The behavior of Mn overlayers on Fe(0 0 1) under the influence of external magnetic fields is investigated. The electronic charge distribution, local magnetic moments as well as their couplings are determined as a function of the external field by solving self-consistently a tight binding Hamiltonian, parameterized to ab initio TBLMTO calculations. Our method allows to trace back the field-dependent average magnetization of the system to its electronic structure and magnetic configuration. We show how in the non-collinear framework the response of the system is markedly different to what is found in the collinear framework. If metastable magnetic configurations exist, the external field can be used for tuning the system between some of them because the system stays in some of those metastable states even after switching off the external field.