High pressure effects on the magnetic and crystal structure of La0.75Ba0.25CoO3

Abstract The crystal and magnetic structure of the La 0.75 Ba 0.25 CoO 3 has been studied as a function of temperature and high pressure up to 8 GPa using neutron powder diffraction. The crystal structure of the compound at room temperature is considered to be single phase rhombohedral (space group R 3 − c ), at T = 50 K the crystal structure is described by two-phase model assuming the coexistence of the orthorhombic ( Imma ) and rhombohedral ( R 3 − c ) phases. The magnetic structure is found to be ferromagnetic with Curie temperature about 200 K and magnetic moment 1.6 μ B per Co ion. Applied external pressure strongly reduces magnetic moment, it decreases down to 0.7 μ B /Co at pressure of 8 GPa. The drop of magnetic moment is associated with a pressure-driven spin state crossover of the cobalt ions from the intermediate spin state to the low spin state.