Effect of pressure on normal and superconducting state properties of iron based superconductor PrFeAsOF (y = 0.12, 0.14).

The effect of high pressure (up to 8 GPa) on normal and superconducting state properties of PrFeAsOF, an 1111-type iron based superconductor close to optimal doped region, has been investigated by measuring the temperature dependence of resistivity. Initially, the superconducting transition temperature (T ) is observed to increase slowly by about 1 K as pressure (P) increases from 0 to 1.3 GPa. With further increase in pressure above 1.3 GPa, T decreases at the rate of ~1.5 K/GPa. The normal-state resistivity decreases monotonically up to 8 GPa. We have also measured the pressure dependence of magnetization (M) on the same piece of PrFeAsOF sample up to 1.1 GPa and observed T as well as the size of the Meissner signal to increase with pressure in this low-pressure region. In contrast, for an over-doped PrFeAsOF sample, magnetization measurements up to 1.06 GPa show that both T and the Meissner signal decrease with pressure. The present study clearly reveals two distinct regions in the dome-shaped (T -P) phase diagram of PrFeAsOF.