Piezoelectricity in quantum rare-earth metallic boron oxides with the coupling between magnetic, electric and elastic subsystem is studied theoretically. It is proved that the change of piezoelectric ...modules of the considered crystals are proportional to components of the quadrupole susceptibility, which determines the external magnetic and electric fields, strain and temperature dependences of that change. We show why holmium compounds manifest the strongest renormalization among other rare-earth ions in this family of crystals. The reason is in the structure of the low energy term of the electron configuration, depending on spins and orbital moments of 4f electrons.
Nitrogen-vacancy colour centres in diamond can undergo strong, spin-sensitive optical transitions under ambient conditions, which makes them attractive for applications in quantum optics, nanoscale ...magnetometry and biolabelling. Although nitrogen-vacancy centres have been observed in aggregated detonation nanodiamonds and milled nanodiamonds, they have not been observed in very small isolated nanodiamonds. Here, we report the first direct observation of nitrogen-vacancy centres in discrete 5-nm nanodiamonds at room temperature, including evidence for intermittency in the luminescence (blinking) from the nanodiamonds. We also show that it is possible to control this blinking by modifying the surface of the nanodiamonds.
Abstract
Quantum triangular-lattice antiferromagnets are important prototype systems to investigate numerous phenomena of the geometrical frustration in condensed matter. Apart from highly unusual ...magnetic properties, they possess a rich phase diagram (ranging from an unfrustrated square lattice to a quantum spin liquid), yet to be confirmed experimentally. One major obstacle in this area of research is the lack of materials with appropriate (ideally tuned) magnetic parameters. Using Cs
2
CuCl
4
as a model system, we demonstrate an alternative approach, where, instead of the chemical composition, the spin Hamiltonian is altered by hydrostatic pressure. The approach combines high-pressure electron spin resonance and r.f. susceptibility measurements, allowing us not only to quasi-continuously tune the exchange parameters, but also to accurately monitor them. Our experiments indicate a substantial increase of the exchange coupling ratio from 0.3 to 0.42 at a pressure of 1.8 GPa, revealing a number of emergent field-induced phases.
Existence of uniform trajectory and uniform global attractors for an incompressible non-Newtonian fluid (namely, for the mathematical model of nonlinearly viscous fluid motion) in 2D and 3D bounded ...domains is studied in this paper. For this aim the topological approximation method is effectively combined with the theory of attractors of trajectory spaces.
This paper is devoted to studying the solvability of one initial boundary value problem describing the motion of aqueous solutions of polymers. This model considers a nonlinearly viscous fluid. The ...existence of weak solutions for the considered problem is considered on the basis of a topological approximation approach. In addition, the problem of optimal feedback control is considered for the studied mathematical model. The existence of the optimal solution providing a minimum for the specified bounded and semicontinuous quality functional is proven.
On the basis of the trajectory pullback attractors theory, this paper studies the dynamics of weak solutions for a nonautonomous model of the polymer solutions motion (with the rheological relation ...satisfying the objectivity principle). For this model, we establish the existence of weak solutions, determine a family of trajectory spaces, introduce the concepts of trajectory and minimal pullback attractors, and prove the existence of these attractors.
PDF
