Sun Li-Ling

Superconductivity at 55 K in Iron-Based F-Doped Layered Quaternary Compound Sm[O1-xFx] FeAs

We report the superconductivity in iron-based oxyarsenide Sm[O1-xFx]FeAs, with the onset resistivity transition temperature at 55.0K and Meissner transition at 54.6 K. This compound has the same crystal structure as LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the highest critical temperature among all materials besides copper oxides up to now.

First-principles study on the elastic properties of platinum nitride

Elastic properties of platinum nitride (PtN) are studied by first-principles calculations with the fully relativistic full potential linearized augmented plane-wave (LAPW) method, the plane-wave ultrasoft pseudopotential (PW-PP) and the projector-augmented wave (PAW) methods. The results reveal that: (1) the scalar relativistic scheme is sufficient to treat the valence electronic structure, i.e. the spin-orbit effect has little effect on the bulk modulus value of platinum nitride; (2) the all-electron full potential method is no more accurate than the pseudopotential and PAW-based methods when calculating the lattice constant and bulk modulus properties of the platinum nitride; (3) platinum nitride in zinc-blende structure is unstable and its crystal structure is still an open problem.

Compression behaviour and equation of state of Zr44.4Nb7Cu13.5Ni10.8Be24.3 bulk metallic glass up to 39 GPa

The compression of Zr44.4Nb7Cu13.5Ni10.8Be24.3 bulk metallic glass (BMG) is investigated at room temperature up to 39 GPa using {in situ} high-pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state of the BMG is obtained by the calculation of the radial distribution function. Pressure-induced structural relaxation is exhibited. It is found that below about 6 GPa, the existence of excess free volume contributes to the rapid structural relaxation, which gives rise to rapid volumetric change, and the structural relaxation results in structural stiffness under higher pressure.

Growth, Characterization and Fermi Surface of Heavy Fermion CeCoIn5 Superconductor

High quality single crystals of heavy Fermion CeCoIn5 superconductor have been grown by flux method with a typical size of (1 − 2) × (1 − 2) × (~ 0.1) mm3. The single crystals are characterized by structural analysis from x-ray diffraction and Laue diffraction, as well as compositional analysis. Magnetic and electrical measurements on the single crystals show a sharp superconducting transition with a transition temperature at Tc,onset ~2.3 K and a transition width of ~0.15K. The resistivity of the CeCoIn5 crystal exhibits a hump at ~45 K, which is typical of a heavy Fermion system. High resolution angle-resolved photoemission spectroscopy (ARPES) measurements of CeCoIn5 reveal clear Fermi surface sheets that are consistent with the band structure calculations when assuming itinerant Ce 4f electrons at low temperature. This work provides important information on the electronic structure of heavy Fermion CeCoIn5 superconductor. It also lays a foundation for further studies on the physical properties and superconducting mechanism of the heavy Fermion superconductors.

Isostructural Transition of MgB2 Under High Pressure

The high-pressure behaviour of the superconductor MgB2 with a hexagonal structure has been investigated by the in situ synchrotron radiation x-ray diffraction method under pressures up to 42.2 GPa in a diamond anvil cell. An abrupt decrease of about 7% in the unit cell volume of this material occurs in the pressure range of 26.3-30.2 GPa. A split of the Raman spectrum was also observed. The jump of the compression curve and Raman spectrum are ascribed to an isostructural transition in MgB2 at a pressure of 30.2 GPa.

Effects of gravity field on glass forming ability in ZrTiCuNiBe alloy

The solidification and glass forming ability of Zr41Ti14Cu12.5Ni10Be22.5 bulk glassy forming alloy is investigated by Bridgman unidirectional solidification at different growth velocities under different gravity field orientations. Large differences in glass formation, undercooling and crystallization morphology on different solidification conditions have been found and discussed from the point of view of gravity induced convection. The results are useful for understanding the nucleation and growth in the melt and glass formation mechanism in the alloy.

Phase transition in Pd40Ni10Cu30P20 bulk metallic glass under HP & HT

The phase transitions in Pd40Ni10Cu30P20 bulk metallic glass (BMG) have been studied under high pressure and high temperature (HP & HT) by X-ray diffaction measurements with synchrotron radiation source. We found that the BMG underwent a phase transitions of amorphous-crystalline-amorphous at 10 GPa upon heating. The parallel experiments were carried out at 7 GPa, while we did not observe the amorphous-crystalline-amorphous transitions by increasing temperature. Quenching the melted BMG at 7 GPa, it was found that the phase crystallized from the melt differed from the primary phase crystallized from the starting amorphous solid upon heating suggesting there existed a distinct mechanism in two cases.

Kinetics of the Glass Transition of the Zr41Ti14Cu12.5Ni10Be22.5 Alloy Solidified in a Drop Tube

Droplets of Zr41Ti14Cu12.5Ni10Be22.5 glass-forming alloy with different sizes are solidified in a drop tube containerless process. The glass transition temperature Tg of Zr41Ti14Cu12.5Ni10Be22.5 glassy spheres solidified with different cooling rates is investigated by using a differential scanning calorimeter. It was found that all the amorphous spheres show an increase of Tg with the heating rate. The glassy spheres have a unique value for the glass transition activation energy Eg = 435.50 kJ/mol, which is independent of cooling rate q. The insensitivity of Tg to q is interpreted by an extension of the free volume model for flow.

Structural relaxation of Pd39Ni10Cu30P21 bulk metallic glass under high pressure

The Pd39Ni10Cu30P21 bulk metallic glass is isothermally relaxed under various pressures. The degree of the structural relaxation is evaluated in terms of the enthalpy recovery behaviours involved in the irreversible glass transition processes by using a temperature-modulated differential scanning calorimetry technique. A roughly Linear increase of the recovery enthalpy is observed within the experimental pressure range fi-om 2.67 to 4.45 GPa, which reflects the release of the frozen-in enthalpy in the as-quenched glass with increasing relaxation pressure. The pressure dependence of the timescale of the enthalpy recovery processes is also exhibited.