The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor

We investigated the nature of the magnetic phase transition in the Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization measurements performed in the magnetic field up to 90 kOe and temperature range 2-200 K showed that the magnetic ordering at temperatures below T = 50 K exhibits features characteristic for both spin-glass and ferromagnetic phases. The modified Sherrington - Southern model was applied to explain the observed transition temperatures. The calculations showed that the spin-glass state is preferred in the range of the experimental carrier concentrations and Mn content. The value of the Mn hole exchange integral was estimated to be J/pd/ = 0.45+/-0.05 eV. The experimental magnetization vs temperature curves were reproduced satisfactory using the non-interacting spin-wave theory with the exchange constant J/pd/ values consistent with those calculated using modified Sherrington - Southern model. The magnetization vs magnetic field curves showed nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of strong magnetic frustration in the system. The experimental results were reproduced theoretically with good accuracy using the molecular field approximation-based model of a disordered ferromagnet with long-range RKKY interaction.Comment: 9 pages, 6 figure

Population Genetics of Perennial Ryegrass (\u3cem\u3eLolium Perenne\u3c/em\u3e L.): Differentiation of Pasture and Turf Cultivars

Cultivar differentiation using molecular markers to assess genetic variation may be of value in obtaining or protecting plant breeders rights. A knowledge of genetic variation and how it is structured within perennial ryegrass (Lolium perenne L.) populations will also help us understand the consequences to fitness and adaptation when implementing molecular breeding strategies. In a study of the population genetic structure of a number of perennial ryegrass varieties we examined the cultivar differentiation potential of marker technology

Magnetoresistance of a semiconducting magnetic wire with domain wall

We investigate theoretically the influence of the spin-orbit interaction of Rashba type on the magnetoresistance of a semiconducting ferromagnetic nanostructure with a laterally constrained domain wall. The domain wall is assumed sharp (on the scale of the Fermi wave length of the charge carriers). It is shown that the magnetoresistance in such a case can be considerably large, which is in a qualitative agreement with recent experimental observations. It is also shown that spin-orbit interaction may result in an increase of the magnetoresistance. The role of localization corrections is also briefly discussed.Comment: 5 pages, 2 figure

Viewing and Reading Behaviour in a Virtual Environment: The Full-Text Download and What Can Be Read Into It

This article aims to focus on usage data in respect to full-text downloads of journal articles, which is considered an important usage (satisfaction) metric by librarians and publishers. The purpose is to evaluate the evidence regarding full-text viewing by pooling together data on the full-text viewing of tens of thousands of users studied as part of a number of investigations of e-journal databases conducted during the Virtual Scholar research programme

Compactness for Holomorphic Supercurves

We study the compactness problem for moduli spaces of holomorphic supercurves which, being motivated by supergeometry, are perturbed such as to allow for transversality. We give an explicit construction of limiting objects for sequences of holomorphic supercurves and prove that, in important cases, every such sequence has a convergent subsequence provided that a suitable extension of the classical energy is uniformly bounded. This is a version of Gromov compactness. Finally, we introduce a topology on the moduli spaces enlarged by the limiting objects which makes these spaces compact and metrisable.Comment: 38 page

Quantum graphs with singular two-particle interactions

We construct quantum models of two particles on a compact metric graph with singular two-particle interactions. The Hamiltonians are self-adjoint realisations of Laplacians acting on functions defined on pairs of edges in such a way that the interaction is provided by boundary conditions. In order to find such Hamiltonians closed and semi-bounded quadratic forms are constructed, from which the associated self-adjoint operators are extracted. We provide a general characterisation of such operators and, furthermore, produce certain classes of examples. We then consider identical particles and project to the bosonic and fermionic subspaces. Finally, we show that the operators possess purely discrete spectra and that the eigenvalues are distributed following an appropriate Weyl asymptotic law