The orthorhombic rare-earth cobaltate ${\mathrm{Nd}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{CoO}}_3$ is studied by neutron powder diffraction. The Co sublattice orders ferromagnetically below $T_c\approx 200$ K with the magnetic moments aligned along the c axis. On cooling, ${\mathrm{Nd}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{CoO}}_3$ revealed an induced ferromagnetic order of the Nd sublattice coupled antiparallel to the Co lattice. Within a simple spin-only picture, steric considerations give evidence for a mixed-valent mixed-spin configuration of the Co ions. This is compared to an intermediate valence-state scenario that shows the necessity of detailed electronic-structure calculations.

• Received 2 March 2001

DOI:https://doi.org/10.1103/PhysRevB.64.224404