The dynamical behaviour of liquids is frequently characterized by the fragility, which can be defined from the temperature dependence of the shear viscosity, η (ref. ). For a strong liquid, the activation energy for η changes little with cooling towards the glass transition temperature, T. The change is much greater in fragile liquids, with the activation energy becoming very large near T. While fragility is widely recognized as an important concept-believed, for example, to play an important role in glass formation-the microscopic origin of fragility is poorly understood. Here, we present new experimental evidence showing that fragility reflects the strength of the repulsive part of the interatomic potential, which can be determined from the steepness of the pair distribution function near the hard-sphere cutoff. On the basis of an analysis of scattering data from ten different metallic alloy liquids, we show that stronger liquids have steeper repulsive potentials.

It is established, using magnetization measurements, that Ni50Mn36.5In13.5 is in a paramagnetic state (PS) above and below the martensitic transition temperature (TM). Magnetoresistance (MR) and magnetic entropy changes (ΔSM) in the vicinity of TM were studied. MR and ΔSM at TM were found to be ≈−8% and ≈+24 J Kg−1 K−1, respectively, at ΔH=5 T. Although MR and ΔSM values were lower than compared to those found in other Heusler systems, the significantly smaller hysteresis observed in Ni50Mn36.5In13.5 makes this compound, and other such compounds that undergo a martensitic transition in a PS, promising for the study and applications of magnetocaloric magnetic materials.

The short-and medium-range order of electrostatically levitated Zr 80 Pt 20 and Zr 77 Rh 23 liquids are presented, based on a combination of high-energy X-ray diffraction and time-of-flight neutron diffraction studies. The atomic structures of the Zr 80 Pt 20 liquids were determined as a function of temperature from constrained reverse Monte Carlo simulations using X-ray and elastic neutron scattering measurements and two partial pair-distribution functions obtained from molecular dynamics simulations. Analysis of both the Faber-Ziman and Bhatia-Thornton partial structure factors shows that the Zr 80 Pt 20 and Zr 77 Rh 23 liquids have similar topological short-range order. Interestingly, the chemical short-range order appears to be much more strongly tied to the topological order in the Zr 77 Rh 23 liquid than in the Zr 80 Pt 20 . These results demonstrate that the combination of experimental scattering measurements with molecular dynamics results provides a powerful approach for obtaining details of chemical and topological ordering in metallic glasses and liquids.

The results of high-energy X-ray scattering studies over a wide temperature range for equilibrium and supercooled Zr x Ni 100 − x (x = 36, 57, 76) liquids and the corresponding glasses are presented. The results of liquid density and viscosity measurements are also shown. All of the liquid studies were made on containerlessly processed liquids using the technique of electrostatic levitation. The scattering data were used to determine the temperature-dependent total structure factor, S(q), and pair-correlation function, g(r). A discontinuity is observed between the magnitude of the first peak in S(q) of the liquid when extrapolated to the glass transition temperature, T g , and the value determined for the structurally relaxed glass at T g . This indicates that the structural ordering in the liquid accelerates upon approaching T g , consistent with the behavior expected for a fragile liquid. An asymmetry in the first peak in the pair correlation function develops with decreasing temperature for all alloy liquids and glasses, suggesting that chemical ordering accompanies the structural ordering.

The effects of the partial substitution of Mn by Co on the magnetic, magnetoelastic, and magnetocaloric properties of Ni 50 Mn 35 In 15 Heusler alloys were studied using x-ray diffraction, temperature and field dependences of the magnetization ͓M͑T,H͔͒, and strain gauge techniques. It was observed that the presence of Ϸ3% Co atoms in Mn sites strongly affected the magnetic and magnetoelastic behaviors of Ni 50 Mn 35 In 15. At H = 5 T, a maximum magnetoelastic strain of Ϸ0.6% was observed for Ni 50 Mn 35 In 15. It was found that Co substituted into the Mn position does not affect the ⌬S M in the vicinity of the second order transitions ͑SOTs͒, however ⌬S M near the first order transitions ͑FOTs͒ it slightly decreases. The net refrigeration capacities in the vicinity of both the FOT and SOT were found to significantly increase by introducing Co into Mn sites. The net refrigeration capacity in the vicinity of the FOT and SOT was found to be 167 J/kg ͑T = 277-293 K͒ and 229 J/kg ͑T = 305-354 K͒, respectively, at a magnetizing field of 5 T. These values of the magnetocaloric parameters are comparable to that of the largest values reported for metallic magnets near room temperature.