75As-nuclear magnetic resonance (NMR) on an iron (Fe)-based superconductor LaFeAsO 1-xF x (x = 0:14) was performed under a pressure of 3 GPa. Enhancement of the superconducting transition temperature (T c) was confirmed from the relaxation rate (1=T 1); T c goes up to 40K by applying pressure up to 3 GPa. 1=T 1T, which is temperature independent just above T c and gives a measure of the density of states (DOS) at the Fermi energy, enhances by applying pressure. These facts suggest that an increase of the DOS leads to the enhancement of T c. On the other hand, anomalous behavior of 1=T 1T observed at high temperatures is suppressed by applying pressure.
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