We have constructed a pressure-temperature (P-T) phase diagram of P-induced superconductivity in EuFe2As2 single crystals via resistivity (ρ) measurements up to 3.2 GPa. As hydrostatic pressure is applied, the temperature T0 where an antiferromagnetic (AF) transition of the Fe moments and a structural phase transition occur shifts to lower temperatures, and the corresponding resistive anomaly becomes undetectable for P≥2.5 GPa. This suggests that the critical pressure Pc where T0 becomes zero is about 2.5 GPa. We have found that the AF order of the Eu2+ moments survives up to 3.2 GPa, the highest pressure in the experiments, without significant changes in the AF ordering temperature T N. The superconducting (SC) ground state with a sharp transition to zero resistivity at Tc~30 K, indicative of bulk superconductivity, emerges in a pressure range from Pc~2.5 to ~3.0 GPa. At pressures close to but outside the SC phase, the ρ(T) curve shows a partial SC transition (i.e., zero resistivity is not attained) followed by a reentrant-like hump at approximately TN with decreasing temperature. When nonhydrostatic pressure with a uniaxial-like strain component is applied using a solid pressure medium, the partial superconductivity is continuously observed in a wide pressure range from 1.1 to 3.2 GPa.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2011 Jun 10|