Effect of high pressure on the crystal and magnetic structures of La0.5Ca0.5CoO3 cobaltite

The atomic and magnetic structures of La0.5Ca0.5CoO3 cobaltite have been studied by the neutron diffraction technique at high pressures of up to 4 GPa in the 10- to 300-K temperature range. The pressure dependences of the structural parameters have been obtained. The Curie temperature increases with the pressure with the coefficient dT (C)/dP = 1 K/GPa, demonstrating the stability of the ground ferromagnetic (FM) state. The pressure dependence of the ground FM state in La0.5Ca0.5CoO3 is in drastic contrast with that for La1 - x Ca (x) CoO3 at a lower calcium content (x < 0.3). For the latter compound, the pressure suppressed the ground FM state and a large negative pressure coefficient of the Curie temperature (dT (C)/dP similar to -10 K/GPa) was observed. The nature of such a phenomenon is analyzed in the framework of the double exchange model also taking into account the changes in the electron configuration of Co3+ ions.