Interplay between effects of external pressure and dilution of the U sublattice in UCoAl-based materials

Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3 GPa suppresses the ferromagnetism and restores the “UCoAl-type” metamagnetism back. However, the metamagnetic transition becomes of the second order instead of the first order one in parent UCoAl. This is attributed to enhancement of fluctuations of the U magnetic moment upon dilution of the U sublattice.