Ac susceptibility studies of the weak itinerant ferromagnet SrRuO3 under high pressure to 34 GPa

The dependence of the Curie temperature T-Curie on nearly hydrostatic pressure has been determined to 17.2 GPa for the weak itinerant ferromagnet SrRuO3 in both polycrystalline and single-crystalline forms. T-Curie is found to decrease under pressure from 162 to 42.7 K at 17.2 GPa in nearly linear fashion at the rate dT(Curie)/dP similar or equal to-6.8 K/GPa. No superconductivity was found above 4 K in the pressure range from 17 to 34 GPa. Room-temperature x-ray diffraction studies to 25.3 GPa reveal no structural phase transition but indicate that the average Ru-O-Ru bond angle beta passes through a minimum near 15 GPa. The bulk modulus and its pressure derivative were determined to be B-o=192(3) GPa and B-o(')=5.0(3), respectively. Parallel ac susceptibility studies on polycrystalline CaRuO3 at 6 and 8 GPa pressure found no evidence for either ferromagnetism or superconductivity above 4 K.