Pressure studies of (La, Sm)FeAsO1−xFx and LaFePO

Pressure dependence on superconducting transition temperature (Tc) was examined for iron-based superconductor LaFeAsO1−xFx, SmFeAsO1−xFx and LaFePO. The Tc’s increase largely for LaFePO and LaFeAsO1−xFx with a small increase of pressure. The electrical resistivity measurements reveal the pressure-induced superconductivity in undoped LaFeAsO and SmFeAsO. X-ray diffraction measurements were also performed under high pressure up to 10 GPa for LaFePO and LaFeAsO1−xFx system, where the anisotropic decrease of the lattice constants was observed with applying pressure.