Neutron diffraction studies have been carried out on a single crystal of oxygen-deficient perovskite TbBaCo2O5.5 in the temperature range of 7-370 K. There have been observed several magnetic or structural transitions. Among these, the existence of the transitions to the insulating phase from the metallic one at ~340 K, to the one with the ferromagnetic moment at ~280 K and possibly to the antiferromagnetic one at ~260 K, with decreasing temperature T correspond to those reported in former works. We have studied the magnetic structures at 270 K and 250 K and found that all Co3+ ions of the CoO6 octahedra are in the low spin state and those of the CoO5 pyramids carry spins which are possibly in the intermediate spin state. Non-collinear magnetic structures are proposed at these temperatures. Two other transitions have also been observed at the temperatures, ~100 K and ~250 K.
@article{arxiv.cond-mat/0301618,
title = {Magnetic Structures of High Temperature Phases of TbBaCo2O5.5},
author = {Minoru Soda and Yukio Yasui and Toshiaki Fujita and Takeshi Miyashita and Masatoshi Sato and Kazuhisa Kakurai},
journal= {arXiv preprint arXiv:cond-mat/0301618},
year = {2009}
}