Surface distortions of the magnetic structure of a uniaxial antiferromagnet: The “magnetic field-roughness” phase diagram

Magnetic-structure distortions induced by an external magnetic field near a rough surface of a uniaxial collinear antiferromagnet are analyzed using mathematical modeling. The “magnetic field-roughness” phase diagram of these distortions is constructed. It is demonstrated that, under specific conditions, the presence of atomic steps leads to the formation of domains in the surface layer of the antiferromagnet. In the case of a strong roughness, there arise static vortices at the surface and a 90° domain wall aligned parallel to the surface of the antiferromagnet.     

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.     

Magnetic structure of the interface between ferromagnet and antiferromagnet with parallel anisotropy axes

The structure of a spin spiral arising in the vicinity of the interface between a ferromagnet and a compensated antiferromagnet is studied in the case where the anisotropy axes of the layers are parallel to each other, and the evolution of this spiral in an external magnetic field is investigated.     

Anisotropy induced by impurities of “random local field” type in <Emphasis Type="Italic">O</Emphasis>(<Emphasis Type="Italic">n</Emphasis>) models and suppression of the Imry–Ma inhomogeneous state

It is shown that in a system with anisotropic distribution of the impurity-induced random local field directions in the n-dimensional space of a vector order parameter with the O(n) symmetry, the impurityinduced effective anisotropy arises for the space dimensionality 2 < d < 4. If the anisotropy constant exceeds the threshold value, then an inhomogeneous state predicted by Imry and Ma becomes energetically unfavorable, and the system goes back to a state with the long-range order.     

Exclusive measurement of the pp --> pppi(+)pi(-) reaction near threshold

The pp-->pp pi(+) pi(-) reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal pp-->pp(*)(1440)-->pp sigma = pp(pi(+)pi(-))(I = l = 0) as the dominant process as well as significant contributions from p(*)-->Delta(++)pi(-)-->psigma. The observed anisotropy in the proton angular dependence is consistent with heavy-meson exchange. In the invariant mass spectra, no narrow structures of statistical relevance (3sigma) are found.     

Quasi-One-Dimensional Ising Models with Defects of the “Random Local Field” Type: the Imry–Ma Phase in Spaces with a Dimension Higher than the Lower Critical Dimensionality

Physics of the Solid State - The “temperature–defect concentration” phase diagram of quasi-one-dimensional Ising models with defects of the “random local field” type...     

Reversible dimerization of 9-cyano-10-methylacridinyl radical

The electrochemical reduction of the 9-cyano-10-methylacridinium cation in acetonitrile yielded the corresponding radical, which was rather stable at 20 °C and gave a resolved ESR spectrum. This radical reversibly dimerized in the temperature range from 20 to −30 °C. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1444–1445, August, 2006.     

Two-dimensional O(n) Models with Defects of “Random Local Anisotropy” Type

Physics of the Solid State - The phase diagram of two-dimensional systems with continuous symmetry of the vector order parameter containing defects of the “random local anisotropy” type...     

Concentration phase transition in systems with weak anisotropy

Systems with weak easy-axis anisotropy, which contain im purities of the type of a “random local field,” have been considered. The anisotropy-constant dependence of the critical concentration of impurities at which the long-range order is destroyed has been obtained for the space-dimension range 2 ≤ d ≤ 4.     

Cubic anisotropy created by defects of “random local anisotropy” type,and phase diagram of the O(n) Model

Physics of the Solid State - The expression for the cubic-type-anisotropy constant created by defects of “random local anisotropy” type is derived. It is shown that the Imry–Ma...