Electrical conductivity and superconductivity of ZrNi 4P 2 and ZrRu 4P 2 prepared at high pressure

Abstract

Ternary metal phosphides ZrNi 4P 2, ZrRu 4P 2 and HfRu 4P 2 have been prepared at high temperatures and high pressures. The X-ray diffraction lines of these compounds are assigned by the index of the ZrFe 4Si 2-type structure. The resistivity of ZrNi 4P 2 decreases rapidly with decreasing temperature. It behaves as a metal. The relation between the electrical properties and the structure in ZrNi 4P 2 is discussed. The superconductivity in ZrRu 4P 2 and HfRu 4P 2 is found at around 11 K and 9.5 K, respectively. These are new superconductors. The T c of 11 K in ZrRu 4P 2 is the highest value obtained during various sample preparations and annealing conditions. The upper critical field ( H c2 ) obtained from H c2 vs temperature curve for ZrRu 4P 2 is 12.2 tesla at 0 K when the midpoint of the resistivity jump is taken as the T c . The superconductivity of ZrRu 4P 2 and HfRu 4P 2 is discussed.