Effect of pressure on the iron arsenide superconductorLixFeAs(x=0.8,1.0,1.1)

Abstract

Resistance measurements of a ``111'' type superconductor ${\text{Li}}_{x}\text{FeAs}$ $(x=0.8,1.0,1.1)$ were performed at high pressure. The superconductivity transition temperature $({T}_{c})$ is found to decrease almost linearly with increasing pressure and the pressure derivative, $d{T}_{c}/dP$, becomes smaller with increasing Li content. Electron spin resonance experiment at ambient pressure on a stoichometric sample shows gradual decrease in the spin moment and the loss of coherence of spin coupling as the temperature is lowered. A very weak Fe local moment is observed when the temperature is lowered to ${T}_{c}$. In situ synchrotron radiation powder x-ray diffraction at high pressure shows changes in the resistivity are not related to a structural transition.