Incommensurate--commensurate transitions in the mono-axial chiral helimagnet driven by the magnetic field

The zero temperature phase diagram of the mono-axial chiral helimagnet in the magnetic field plane formed by the components parallel and perpendicular to the helical axis is thoroughly analyzed. The nature of the transition to the commensurate state depends on the angle between the field and the helical axis. For field directions close to the directions parallel or perpendicular to the helical axis the transition is continuous, while for intermediate angles the transition is discontinuous and the incommensurate and commensurate states coexist on the transition line. The continuous and discontinuous transition lines are separated by two tricritical points with specific singular behaviour. The location of the continuous and discontinuous lines and of the tricritical points depend strongly on the easy-plane anisotropy, the effect of which is analyzed. For large anisotropy the conical approximation locates the transition line very accurately, although it does not predict the continuous transitions nor the tricitical behaviour. It is shown that for large anisotropy, as in CrNb3S6, the form of the transition line is universal, that is, independent of the sample, and obeys a simple equation. The position of the tricritical points, which is not universal, is theoretically estimated for a sample of CrNb3S6Comment: 10 pages, 9 figure

Compositional dependence of thermal and mechanical properties of quaternary Zr-Cu-Ni-Al bulk glassy alloys

To determine the optimized composition of quaternary Zr-Cu-Ni-Al bulk glassy alloy, its thermal and mechanical properties are examined. Zr shows high correlation coefficients with T g and Vickers hardness, whereas Ni and Al show high correlation coefficients with T l and T x , respectively. Only Cu shows no remarkable correlation coefficient with any thermal or mechanical properties. We conclude that a compositional region with a high (over 135 kJ/m 2 ) U-notch Charpy impact (CUE) value is located around the Zr 52 Cu 30 Ni 8 Al 10 bulk glassy alloy, which exhibits a maximum CUE of 165 kJ/m 2 . Moreover, a compositional region with high tensile strength (over 2000 MPa) is also located around the Zr 48 Cu 32 Ni 8 Al 12 bulk glassy alloy, which shows a maximum tensile strength of 2100 MPa

Molecular Dynamics of Yukawa System (Dust Plasma) with Deformable Periodic Boundary Conditions: Formulation

Molecular dynamics of the Yukawa system, the system of particles interacting via the Yukawa or the screened Coulomb potential, are formulated for various statistical ensembles and external conditions. The Yukawa potential smoothly interpolates the long-range Coulomb and the short-range interactions by adjusting a single parameter, the screening length. In order to reduce the effect of boundaries, the periodic boundary conditions are imposed and the deformations of the fundamental vectors of periodicity are taken into account. Ewald-type expressions for interaction energy, force, and kinematic pressure are given explicitly

Elastic properties of Zr-based bulk metallic glasses studied by resonant ultrasound spectroscopy

We report measurements of the elastic properties of Zr-based bulk metallic glasses, Zr52.5Cu17.9Ni14.6Al10Ti5, Zr50Cu30Ni10Al10, and Zr50Cu40Al10 between 5 K and 300 K. Both the shear and longitudinal modulus have been measured as a function of temperature, allowing accurate determination of the Poisson’s ratio and the related ratio of bulk modulus to shear modulus, K/G. These data make it possible to assess the influence of the alloy’s composition on the mechanical properties and enable an evaluation of the correlation between the elastic moduli and the ductility of the alloys