Thermodynamic study on non-centrosymmetric superconductor UIr by ac calorimetry under high pressure

Tateiwa, Naoyuki   ; Haga, Yoshinori   ; Matsuda, Tatsuma; Yamamoto, Etsuji  ; Ikeda, Shugo; Onuki, Yoshichika*

We investigated non-centrosymmetric compounds CePtSi and UIr by the ac heat capacity measurement under pressures. The pressure phase diagrams are determined. In CePtSi, the Nel temperature = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The phase diagram of CePtSi is thus very unique. In the ferromagnetic compound UIr where successive ferromagnetic transitions appear under pressure, the heat capacity shows an anomaly at the Curie temperature and this anomaly shifts to lower temperatures with increasing pressure. The present pressure dependence of was consistent with the previous works by the resistivity and magnetization measurements.