High-pressure diffraction studies on Ca2RuO4 -: art. no. 094104

We studied the crystal and magnetic structure of Ca2RuO4 as function of pressure with different diffraction techniques. The first-order phase transition observed at a moderate pressure of P=0.5 GPa between the insulating and the metallic high-pressure phase is characterized by a broad region of phase coexistence. The following structural changes are observed as function of pressure: (a) A discontinuous change of both the tilt and rotational angle of the RuO6-octahedra at this transition, (b) a gradual decrease of the tilt angle in the high-pressure phase (P>0.5 GPa), and (c) the disappearance of the tilt above 5.5 GPa leading to a higher symmetry structure. The magnetism was studied by single-crystal neutron diffraction: The ferromagnetic component of the high-pressure phase and a rearrangement of antiferromagnetic order in the low-pressure phase have been observed.