Magnetic property in the ferromagnetic superconductor UGe at pressures above the ferromagnetic critical pressure

Tateiwa, Naoyuki   ; Haga, Yoshinori   ; Matsuda, Tatsuma; Yamamoto, Etsuji  ; Onuki, Yoshichika; Fisk, Z.

UGe is a ferromagnet with the Curie temperature of 54 K at ambient pressure. The superconductivity appears in the pressure region of 1.0-1.6 GPa where UGe is in the ferromagnetic state. Ferromagnetic state disappears above =1.6 GPa. In this study, we have measured the dc-magnetization up to 4.1 GPa using the ceramic anvil high pressure cell. We confirmed the maximum at in the temperature dependence of the dc magnetic susceptibility. With increasing pressure, is increased from 24 K at 1.9 GPa to 32 K at 2.6 GPa. The peak structure around becomes broader with increasing pressure and disappears above 4 GPa. The metamagnetic transition field increases rapidly with increasing pressure. We discuss the experimental results with the phenomenological spin-fluctuation theory.