Generalized Gibbs Phase Rule and Multicriticality Applied to Magnetic Systems

A generalization of the original Gibbs phase rule is proposed in order to study the presence of single phases, multiphase coexistence, and multicritical phenomena in lattice spin magnetic models. The rule is based on counting the thermodynamic number of degrees of freedom, which strongly depends on the external fields needed to break the ground state degeneracy of the model. The phase diagrams of some spin Hamiltonians are analyzed according to this general phase rule, including general spin Ising and Blume–Capel models, as well as q-state Potts models. It is shown that by properly taking into account the intensive fields of the model in study, the generalized Gibbs phase rule furnishes a good description of the possible topology of the corresponding phase diagram. Although this scheme is unfortunately not able to locate the phase boundaries, it is quite useful to at least provide a good description regarding the possible presence of critical and multicritical surfaces, as well as isolated multicritical points.

RARE-EARTH PERMANENT MAGNETS AND THEIR APPLICATION IN MAGNETIC SYSTEMS OF TECHNOLOGICAL ELECTRON ACCELERATORS

High performance rare-earth permanent magnets become crucial components of modern electron accelerators. PLP (pressless process) method was described as the advanced production step in the current rare-earth permanent magnet manufacturing. The radiation resistance of SmCo and Nd-Fe-B magnets under electron beam with 10 and 23 MeV and bremsstrahlung were studied. Dipole magnetic systems on the base of rare-earth permanent magnets were designed for the technological electron accelerators at NSC KIPT.

Unveiling electronic and magnetic properties of Cu3(SeO3)2Cl2 and Cu3(TeO3)2Br2 oxohalide systems via first-principles calculations

Here, we report a theoretical investigation of the electronic and magnetic properties of two oxohalide compounds, namely Cu3(SeO3)2Cl2 and Cu3(TeO3)2Br2, using Density Functional Theory (DFT). These layered systems are characterized by two inequivalent Cu sites, with CuO4 and CuO4X (X = Cl, Br) environments, respectively. A new magnetic model is proposed through the calculation of the magnetic exchange couplings. Our study discloses the participation of the Se and Te lone-pairs to the long-range magnetic order, providing potential key informations for future chemical design of original magnetic systems.

Dynamic Dipolar Field of Spin Waves in Low-Dimensional Magnetic Systems: The Effects of Translational Symmetry Breaking

Magnon scatterings affect the performance of magnonic devices directly, and dynamic dipolar field (DDF) is crucial in the scattering potential. In this paper, a theoretical model of the DDF in low-dimensional magnetic systems is present, and simulations give the summation area to achieve good accuracy in the DDF calculation, though the dipolar field is a long-range interaction. Calculation in a finite-size thin film indicates that due to the breaking of translational symmetry, the DDF increases evidently in the borders and the corners. The DDF near the vertex of the thin film is several orders magnitude higher than that in the inside area, making the corners prominent in the magnon scatterings.

Formulation And Evaluation Of Floating Microspheres Of Cefdinir

Various approaches have been used to retain the dosage form in the stomach as a way ofincreasing the gastric residence time (GRT), including floatation systems; high-density systems; mucoadhesive systems; magnetic systems; unfoldable, extendible, or swellable systems; andsuperporous hydrogel systems. The aim of this study was to prepare and evaluate floatingmicrospheres of cefdinir for the prolongation of gastric residence time. Themicrospheres were prepared byCapillary Extrusion method.A full factorial design was applied to optimize the formulation. The optimum batch of microsphere exhibited smooth surfaces with good flow and packing properties, prolonged sustained drug release, remained buoyant for more than 12 hrs, high entrapment efficiency upto68%.Scanning electron microscopy confirmed the hollown structure with particle size in the order of190 μm. The studies revealed that increase in concentration of gum Karaya increased the drug release from the floating microspheres.