Electrical Resistivity Measurements on the International Space Station for the Studies of Dynamics in Metallic Liquids

In addition to its fundamental importance, the electrical resistivity plays a very important role in the studies of various types of thermal excitations (phonons, excitons, magnons) and phase transitions (structural, magnetic, electronic, superconducting) in crystalline solids. It is also useful in amorphous materials for studying the glass transition, structural relaxations, and glass-crystal transformations. In comparison, studies of liquids, especially high-melting temperature metallic liquids, are less common. Severe contaminations due to chemical reaction with the probe and container material handicap such measurements. Rapid crystallization prevents studies of supercooled metastable liquids in containers. In this book chapter, we describe a new powerful tool for studying the resistivity of metallic liquids, the electromagnetic levitator (EML) on the International Space Station (ISS), ISS-EML. This technique allows measurements to be made in levitated equilibrium and supercooled metallic liquids. The most important observation that was made recently is the saturation of resistivity above a characteristic temperature, T_A. Previous experimental and molecular dynamics (MD) simulation studies identified T_A as a crossover temperature, where the dynamical properties (viscosity, diffusion coefficient) start to deviate from a high-temperature Arrhenius-type temperature dependence with a constant activation energy (η = η₀ exp (E/k_BT)) to a temperature-dependent activation energy. According to MD simulations, this happens when the atomic dynamics changes from single particle to cooperative excitations of atoms. Although the exact mechanism for the saturation of resistivity is not fully understood, some qualitative arguments are presented here to explain this and its connection with liquid dynamics.