Magnetic properties of the 5fitinerant electron metamagnet UCoAl under high pressure

The magnetization and susceptibility of single-crystalline UCoAl were measured under high pressures to P=1.2 GPa. A sharp metamagnetic transition was observed only in magnetic fields along the c axis. The critical field is $B_c$=0.65 T at P=0 GPa, which increases with pressure and temperature. The susceptibility for ambient pressure shows a broad maximum at $T_{\max }$=20 K. The value of $T_{\max }$ increases with pressure. A theory of the itinerant metamagnetic transition has been generalized for the case of anisotropic spin fluctuations. The observed pressure dependence of the inverse susceptibility at $T_{\max },$ the temperature $T_0$ for the disappearance of the metamagnetic transition, and the temperature dependence of $B_c$ can be explained with this theory.