High-pressure effects on the crystal and magnetic structure of the Nd0.78Ba0.22CoO3 cobaltite

The crystal and magnetic structure of the Nd (0.78) Ba (0.22) CoO (3) cobaltite is studied by neutron diffraction at high pressures up to 4.2 GPa in the temperature range 10 - 300 K. The pressure dependences of structural parameters are obtained. Ferromagnetic ordering of the Co sublattice is observed at normal pressure below T-C similar to 140 K, and ferrimagnetic ordering of the Co and Nd sublattices with an antiparallel direction of magnetic moments appears at T (F) similar to 40 K. The magnetic moment of Co and the temperature T (C) change slightly under pressure, which points to the stability of the initial intermediate- spin ( S = 1) state of Co (3+) ions. This behavior differs considerably from the characteristic behavior of cobaltites that are close in chemical composition and structure and exhibit ferromagnetic ordering of only the Co sublattice. In these cobaltites, the magnetic moment of Co is substantially suppressed and T-C decreases under pressure, which is related to the change in the state of Co 3(+) ions from the intermediate spin state to the nonmagnetic low- spin state ( S = 0). The interplay between the appearance of the magnetic interaction of the R - Co sublattices and the stability of the spin state of Co (3+) ions in the Nd (0.78) Ba (0.22) CoO (3) cobaltite is discussed.