Superconductivity of binary and ternary molybdenum phosphides prepared at high pressure

Binary and ternary molybdenum phosphides have been prepared at temperatures between 1200 and 1700 degreesC under 4 GPa. An electrical resistivity and a de magnetic susceptibility of the molybdenum phosphides were measured at low temperatures. The superconducting transition temperatures (T-c's) of bi nary molybdenum phosphides are 7 K for Mo3P, 5.8 K for Mo8P5 and 3 K for Mo 4P3. Phosphorus-rich compounds MoP, MoP2 and MoP4 do not show the supercond uctivity down to 2 K. Ternary molybdenum phosphides MoNiP and MoRuP show th e superconducting transition at around 15.5 K. The superconductivity in MoN iP and MoRuP is due to the Mo 4d electrons. The Mo-Mo bonds in the molybden um phosphides are very important for the enhancement of the superconductivi ty. (C) 2001 Elsevier Science B.V. All rights reserved.