Neutron diffraction studies have been carried out on a single crystal of oxygen-deficient perovskite NdBaCo2O5:5 in the temperature (T) range between 7K and 320 K. We have found a magnetic transition at Tc ~ 170 K, and a rapid change of the intensities of several reflections at Tc ~ 30 K. The magnetic structures have been analyzed at 7K (< Tc) and 40K (Tc < T < Tc). Non-collinear magnetic structures, which are based on the G-type antiferromagnetic structure, are proposed at these temperatures. In the T region between T* and Tc, Co3+ ions of CoO6 octahedra are in the intermediate spin state, and those of CoO5 pyramids are in the high spin state. In the region of T < Tc, the magnitude of the Co3 spins in the octahedra decreases gradually as T decreases, suggesting that the spin state approaches the low spin state. It is pointed out that the spin state of Co ions depends on the local structure around them.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)