Compressibility anomaly in the superconducting material Nb3Al under high pressure

Nb3Al, which is widely used in high field magnets, was studied under a range of pressures up to 39.5 GPa using diamond anvil cell. The Nb3Al superconductor is structurally stable up to the highest pressure of the present investigation from previous reports. However, an anomaly of the compressibility beyond 19.2 GPa was detected in the pressure versus volume plot. The curve of volume versus pressure shows the existence of a plateau around 18.0 GPa as seen in several other highly correlated electrons systems, The observed pressure-induced isostructural phase transition was accomplished with a volume inclination without any symmetrical change (space group, Wyckoff position). The physical mechanism behind this isostructural phase transition is the interesting issue for further studies.