Superconducting Properties of GdFeAsO0.85 at High Pressure

Abstract

We report hydrostatic pressure studies up to 5.3 GPa on pressure synthesized GdFeAsO0.85 polycrystalline sample by electrical resistivity, magnetic ac-susceptibility, and ac-specific heat measurements. The superconducting transition temperature (TC) is suppressed dramatically from 53 K at ambient pressure to 36 K at 5.3 GPa. We find that the magnetic ordering temperature (TN=2.4 K) of Gd sublattice determined by specific heat is nearly pressure independent. Also, the superconducting volume fraction estimated by ac-susceptibility data does not change in the pressure range studied. At ambient pressure, the specific heat jump at the TCΔC/TC = 18.3 mJ/mole K2 is comparable to that found in SmFeAsO0.85F0.15 and SmFeAsO0.6. At high pressure, the amplitude of the specific heat jump decreases together with the decrease of TC and conforms with the universal scaling law of (Formula presented.) found in a number of 122 iron pnictide superconductors.